ASTM D7759/D7759M-21

Standard Guide for Nuclear Surface Moisture and Density Gauge Calibration

SIGNIFICANCE AND USE
5.1 Gauge calibration is performed for the following purposes:  
5.1.1 When necessary, to compute the calibration constants of a density calibration equation that relates the gauge density system response (the “density count”) to the soil-equivalent density of the standard on which this response is elicited.  
5.1.2 When necessary, to compute the calibration constants of a water content calibration equation that relates the gauge water content system response (the “water content count”) to the water mass per unit volume value of the standard on which this response is elicited.  
5.1.3 To establish the relationship between the density measured by the gauge to the soil-equivalent density of the standard on which this response is elicited.  
5.1.4 To establish the relationship between the water mass per unit volume measured by the gauge to the water mass per unit volume of the standard on which this response is elicited.  
5.1.5 To ensure that the gauge has an in-place density gauge precision level that is consistent with typical gauge response.  
5.1.6 To ensure that the gauge has an in-place water mass per unit volume gauge precision level that is consistent with typical gauge response.  
5.2 Gauge verification is performed for the following purposes:  
5.2.1 To indicate to the party or agency performing the verification when the mathematical relationship between the in-place density reading indicated by the gauge and the corresponding gauge density test count needs to be adjusted so that the gauge measurement errors do not exceed the specified absolute maximum measurement error for the calibration method used.  
5.2.2 To indicate to the party or agency performing the verification when the mathematical relationship between the water mass per unit volume indicated by the gauge and the corresponding gauge water content test count needs to be adjusted so that the gauge measurement errors do not exceed the specified absolute maximum measurement error for the cal...
SCOPE
1.1 Procedure A—This guide describes the process and objective of formulating the mathematical relationship between the density system count of a nuclear surface moisture and density gauge and the corresponding wet density value of the density standard upon which the density system response was observed.  
1.2 Procedure B—This guide describes the process and objective of comparing the wet density measured by a nuclear surface moisture and density gauge and the corresponding density value of the density standard upon which the density system response was observed.  
1.3 This guide describes the process and objective of the verification of the measurements of a nuclear surface moisture and density gauge.  
1.4 Procedure A—This guide describes the process and objective of formulating the mathematical relationship between the water content system count of a nuclear surface moisture and density gauge and the corresponding water mass per unit volume value of the water content standard upon which the water content system response was observed.  
1.5 Procedure B—This guide describes the process and objective of comparing the water mass per unit volume measured by a nuclear surface moisture and density gauge and the corresponding water mass per unit volume of the corresponding water content standard upon which the water content system response was observed.  
1.6 This guide describes the process and objective of the verification of the measurements of a nuclear surface moisture and density gauge.  
1.7 This guide describes two mathematical processes by which the gauge measurement precision may be computed or measured.  
1.8 This guide offers guidance for developing and reporting estimates of uncertainties in measurements made with gauges that have undergone calibration and verification.  
1.9 All observed and calculated values shall conform to the guide for significant digits and rounding established in Practice D6026.  
...

General Information

• Status: Published
• Publication Date: 30-Apr-2021
• ICS: 17.040.30 - Measuring instruments
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.08 - Special and Construction Control Tests

Relations

• Refers: ASTM D3740-23 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Nov-2023
• Refers: ASTM D3740-19 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Oct-2019
• Refers: ASTM D2216-19 - Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• Effective Date: 01-Mar-2019
• Refers: ASTM D8167/D8167M-18 - Standard Test Method for In-Place Bulk Density of Soil and Soil-Aggregate by a Low-Activity Nuclear Method (Shallow Depth)
• Effective Date: 15-May-2018
• Refers: ASTM D6938-17 - Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• Effective Date: 01-Mar-2017
• Refers: ASTM D6938-15 - Standard Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• Effective Date: 01-Aug-2015
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM D3740-12a - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-May-2012
• Refers: ASTM D3740-12 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Mar-2012
• Refers: ASTM D3740-11 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Sep-2011
• Refers: ASTM D653-11 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Sep-2011
• Refers: ASTM D7013/D7013M-11 - Standard Guide for Calibration Facility Setup for Nuclear Surface Gauges
• Effective Date: 15-Feb-2011
• Refers: ASTM D2216-10 - Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• Effective Date: 01-Jul-2010
• Refers: ASTM D6938-10 - Standard Test Method for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
• Effective Date: 01-May-2010
• Refers: ASTM D3740-10 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Mar-2010

Overview

ASTM D7759/D7759M-21, "Standard Guide for Nuclear Surface Moisture and Density Gauge Calibration," provides comprehensive guidance for the calibration and verification of nuclear surface moisture and density gauges. Developed by ASTM International, this standard is essential for ensuring that nuclear gauges deliver accurate, consistent measurements of soil density and moisture content in geotechnical and construction practices. Calibration and verification are critical for aligning gauge readings with recognized reference standards, minimizing measurement uncertainty, and maintaining compliance with project specifications and regulatory requirements. This guide is applicable to manufacturers, users, and independent calibration vendors engaged in soil and rock testing and inspection.

Key Topics

• Calibration of Density and Moisture Systems:
  • Establishes mathematical relationships-the calibration equations-linking gauge responses to known values for soil density and moisture.
  • Outlines two main procedures:
    • Procedure A: Formulates calibration equations by fitting data from multiple standards.
    • Procedure B: Directly compares measurements to the standard values for verification.
• Verification of Gauge Performance:
  • Describes processes for confirming the accuracy of previously calibrated gauges.
  • Ensures that measurement errors are within specified maximum permissible limits.
• Measurement Uncertainty:
  • Offers methods for calculating and reporting the uncertainty associated with gauge readings at various density and moisture levels.
  • Guides estimation and documentation practices for improved data reliability.
• Significance and Use:
  • Validates that the gauge maintains required precision for both density and water mass per unit volume.
  • Indicates when calibration constants or relationships should be updated to avoid exceeding allowable measurement errors.
• Safety and Regulatory Compliance:
  • Highlights the importance of trained personnel, proper maintenance, and adherence to safety protocols due to the use of radioactive materials.
  • Recommends conformance with supporting ASTM standards for terminology, measurement, and agency competency.

Applications

ASTM D7759/D7759M-21 is widely applied in:

• Construction Quality Assurance:
  • Used on site to verify soil compaction and moisture content, supporting quality assurance and control for infrastructure projects.
• Geotechnical Investigations:
  • Assists in calibrating devices used to determine key soil characteristics required for design and analysis.
• Routine Gauge Maintenance:
  • Guides regular calibrations and verifications post-manufacture, after repairs, or at established intervals to maintain the integrity of readings.
• Regulatory and Contract Compliance:
  • Supports contractors and agencies in meeting project specifications and industry regulations regarding measurement accuracy for earthworks and compaction control.
• Laboratory and Field Testing:
  • Applicable to both laboratory reference checks and on-site measurements, ensuring continuity and consistency across operational environments.

Related Standards

The following related ASTM standards are frequently referenced alongside ASTM D7759/D7759M-21:

• ASTM D653 - Terminology Relating to Soil, Rock, and Contained Fluids
• ASTM D2216 - Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• ASTM D3740 - Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock
• ASTM D6026 - Using Significant Digits in Geotechnical Data
• ASTM D6938 - In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods
• ASTM D7013/D7013M - Calibration Facility Setup for Nuclear Surface Gauges
• ASTM D8167/D8167M - In-Place Bulk Density of Soil and Soil-Aggregate by a Low-Activity Nuclear Method

These standards collectively ensure robust procedures and performance in soil testing using nuclear gauge technology.

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Keywords:
ASTM D7759, nuclear gauge calibration, density gauge verification, moisture gauge calibration, soil density measurement, water content measurement, calibration standard, measurement uncertainty, soil testing standard

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7759/D7759M − 21
Standard Guide for
Nuclear Surface Moisture and Density Gauge Calibration
This standard is issued under the fixed designation D7759/D7759M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 1.7 This guide describes two mathematical processes by
which the gauge measurement precision may be computed or
1.1 Procedure A—This guide describes the process and
measured.
objectiveofformulatingthemathematicalrelationshipbetween
the density system count of a nuclear surface moisture and
1.8 This guide offers guidance for developing and reporting
density gauge and the corresponding wet density value of the
estimates of uncertainties in measurements made with gauges
density standard upon which the density system response was
that have undergone calibration and verification.
observed.
1.9 All observed and calculated values shall conform to the
1.2 Procedure B—This guide describes the process and
guide for significant digits and rounding established in Practice
objective of comparing the wet density measured by a nuclear
D6026.
surface moisture and density gauge and the corresponding
1.10 Units—The values stated in either SI units or inch-
density value of the density standard upon which the density
pound units are to be regarded separately as standard. The
system response was observed.
values stated in each system are not necessarily exact equiva-
1.3 This guide describes the process and objective of the
lents; therefore, to ensure conformance with the standard, each
verification of the measurements of a nuclear surface moisture
system shall be used independently of the other, and values
and density gauge.
from the two systems shall not be combined.Within the text of
1.4 Procedure A—This guide describes the process and
this standard, SI units appear first followed by the inch-pound
objectiveofformulatingthemathematicalrelationshipbetween
(or other non-SI) units in brackets.
the water content system count of a nuclear surface moisture
1.10.1 Reporting of test results in units other than SI shall
and density gauge and the corresponding water mass per unit
not be regarded as nonconformance with this guide.
volume value of the water content standard upon which the
1.11 This standard does not purport to address all of the
water content system response was observed.
safety concerns, if any, associated with its use. It is the
1.5 Procedure B—This guide describes the process and
responsibility of the user of this standard to establish appro-
objective of comparing the water mass per unit volume
priate safety, health, and environmental practices and deter-
measured by a nuclear surface moisture and density gauge and
mine the applicability of regulatory limitations prior to use.
the corresponding water mass per unit volume of the corre-
1.12 This guide offers an organized collection of informa-
sponding water content standard upon which the water content
tion or a series of options and does not recommend specific
system response was observed.
course of action. This document cannot replace education or
1.6 This guide describes the process and objective of the
experienceandshouldbeusedinconjunctionwithprofessional
verification of the measurements of a nuclear surface moisture
judgment. Not all aspects of this guide may be applicable in all
and density gauge.
circumstances. This ASTM standard is not intended to repre-
sent or replace the standard of care by which the adequacy of
a given professional service must be judged, nor should this
This practice is under the jurisdiction of ASTM Committee D18 on Soil and
Rock and is the direct responsibility of Subcommittee D18.08 on Special and
document be applied without consideration of a project’s many
Construction Control Tests.
unique aspects. The word “Standard” in the title of this
Current edition approved May 1, 2021. Published June 2021. Originally
document means only that the document has been approved
approved in 2012. Last previous edition approved in 2014 as D7759–14. DOI:
through the ASTM consensus process.
10.1520/D7759-21.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7759/D7759M − 21
1.13 This international standard was developed in accor- 3.2.5 prepared standards, n—density or water content mea-
dance with internationally recognized principles on standard- surement standards prepared of soil, solid rock, concrete, and
ization established in the Decision on Principles for the engineeredmaterials,thathavedensityorwatercontentvalues,
Development of International Standards, Guides and Recom- or both, that are established and known to a specified uncer-
mendations issued by the World Trade Organization Technical tainty.
Barriers to Trade (TBT) Committee.
3.2.6 soil-equivalent density, n—the density of an average
soil (where an “average soil” is defined herein to have a Z/A
2. Referenced Documents
value of 0.5) that yields the same gauge density count response
2.1 ASTM Standards:
as a metallic calibration standard; Z is the average atomic
D653 Terminology Relating to Soil, Rock, and Contained
number of a material andAis the average atomic mass number
Fluids
of that same material.
D2216 Test Methods for Laboratory Determination of Water
3.2.7 water content system calibration, n— a set of pro-
(Moisture) Content of Soil and Rock by Mass
cesses by which, for each water content standard used in the
D3740 Practice for Minimum Requirements for Agencies
process, a water mass per unit volume indication (gauge count
Engaged in Testing and/or Inspection of Soil and Rock as
orwatermassperunitvolumevalue)isobtainedbythenuclear
Used in Engineering Design and Construction
gauge on the water content standard, and a relationship is
D6026 Practice for Using Significant Digits in Geotechnical
established between the indication of the gauge and the water
Data
mass per unit volume value of the standard; the uncertainty of
D6938 TestMethodsforIn-PlaceDensityandWaterContent
the standard and the indications must be established.
of Soil and Soil-Aggregate by Nuclear Methods (Shallow
3.2.8 water mass per unit volume calibration equation,
Depth)
n—the mathematical function that relates the water mass per
D7013/D7013M Guide for Calibration Facility Setup for
unit volume of the medium under measurement by the gauge
Nuclear Surface Gauges
(the independent variable) to the water content system count
D8167/D8167M Test Method for In-Place Bulk Density of
response of the gauge (the dependent variable).
Soil and Soil-Aggregate by a Low-Activity Nuclear
Method (Shallow Depth) 3.2.9 water content system verification, n—a set of pro-
cesses by which the acceptability of the water mass per unit
3. Terminology
volume calibration equation of a gauge is determined.
3.1 Definitions—See Terminology D653 for general defini-
4. Summary of Practice
tions. For definitions of common metrology terms used in this
standard, refer to the VIM—International Vocabulary of Me-
4.1 The summary of the practice is as follows:
trology.
4.1.1 Procedure A—For new gauges and gauges that fail to
3.2 Definitions of Terms Specific to This Standard: meet the required density system verification criteria, for each
affected index rod position one must perform a density
3.2.1 density system calibration, n—a set of processes by
which, for each density standard used in the process, a density calibration in which one relates the gauge density system
response (the gauge counts) to the soil-equivalent density of
indication (gauge count or gauge density response) is obtained
bythenucleargaugeonthedensitystandard,andarelationship the standard(s) on which the response is elicited and, in a
is established between the indications of the gauge and the second step, uses this information to establish a calibration
density of the standard; the uncertainty of the standard and the equation.
indication must be established.
4.1.1.1 The measurement uncertainties of the density stan-
dard(s) and the gauge density system counts must be known.
3.2.2 density calibration equation, n—the mathematical
4.1.1.2 The standard(s) used for the determination of uncer-
function that relates the density of the medium under measure-
taintyshallberepresentativeoftherangeofdensitiesforwhich
ment by the gauge (the independent variable) to the density
the gauge will be used.
system count response of the gauge (the dependent variable).
4.1.1.3 The mode of density calibration just described is not
3.2.3 density system verification, n—a set of processes by
limited to new gauges or gauges that fail to meet the required
which the acceptability of the associated density calibration
density system verification criteria.
equation of a gauge is determined.
4.1.2 Procedure B—Forgaugeindexrodpositionsforwhich
3.2.4 nuclear gauge, n—a device containing one or more
a density calibration equation has been formulated, one has the
radioactive sources used to measure certain properties of soil
option of performing a density calibration in which one
and soil-aggregates.
establishes the relation between the soil-equivalent density
values of the necessary number of soil-equivalent density
standard(s) and the corresponding soil-equivalent density mea-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
sured by the gauge when used to measure the standards and, in
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
asecondstep,usesthisinformationtoestablishtherelationship
the ASTM website.
between these two density values.
International vocabulary of metrology—Basic and general concepts and
4.1.2.1 The measurement uncertainties of the density stan-
associated terms (VIM), 3rd Edition. Joint Committee for Guides in Metrology,
2012. https://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2012.pdf dards and the density measured by the gauge must be known.
D7759/D7759M − 21
4.1.2.2 The standard(s) used for the determination of uncer- However, for any method that is used in the density system
taintyshallberepresentativeoftherangeofdensitiesforwhich calibration process, one must know the uncertainties of the wet
the gauge will be used. density readings measured by devices calibrated in this manner
4.1.3 The objective of density system verification is to over the range of density values for which the gauge will be
used.
evaluate the current density calibration equation for the gauge
and determine if new calibration constants are required.
4.2.3 The water content calibration equation that relates the
4.1.4 Procedure A—For new gauges and gauges that fail to water mass per unit volume value measured by the gauge on a
meet the required water content system verification criteria,
test site (the “independent variable”) with the water mass per
one must perform a water content calibration in which one unit volume test count measured by the gauge on the test site
establishestherelationbetweenthewatermassperunitvolume
(the “dependent variable”) is typically linear in form, with two
of the necessary number of water content standard(s) and the fit coefficients.
corresponding water system gauge counts elicited from the
4.3 Historically, the most successful method for computing
gauge when used to measure these standards and, in a second
the water content calibration equation of a gauge is by taking
step, uses this information to establish a calibration equation.
readingsontwowatercontentstandards(oneofwhichisazero
4.1.4.1 The measurement uncertainties of the water content
water content standard), combining the independent and de-
standard(s) and the gauge counts must be known.
pendent variables into data pairs, and computing the fit
4.1.4.2 The standard(s) used for the determination of uncer-
coefficients.
tainty shall be representative of the range of water mass per
4.3.1 The computation of the water content calibration
unit volume for which the gauge will be used.
equation is not necessarily limited to the process described in
4.1.4.3 The mode of water content system calibration just
4.3. However, for any method that is used in the water content
described is not limited to new gauges or gauges that fail to
system calibration process, one must know the uncertainties of
meet the required water content system verification criteria.
the water mass per unit volume readings measured by devices
4.1.5 Procedure B—For gauges for which the calibration
calibrated in this manner over the range of water mass per unit
constants of a water mass per unit volume calibration equation
volume values for which the gauge will be used.
have been formulated, one may perform a water content
4.4 See Appendix X1 for a flowchart of the calibration and
calibration in which one establishes the relation between the
verification processes.
water mass per unit volume value of the necessary number of
water content standard(s) and the corresponding water mass
5. Significance and Use
per unit volume measured by the gauge when used to measure
these standard(s) and, in a second step, uses this information to
5.1 Gauge calibration is performed for the following pur-
establish the relationship between these two water mass per
poses:
unit volume values.
5.1.1 When necessary, to compute the calibration constants
4.1.5.1 The measurement uncertainties of the water content
of a density calibration equation that relates the gauge density
standards and the water mass per unit volume measured by the
system response (the “density count”) to the soil-equivalent
gauge must be known.
density of the standard on which this response is elicited.
4.1.5.2 The standards used for the determination of uncer-
5.1.2 When necessary, to compute the calibration constants
tainty shall be representative of the range of water mass per
of a water content calibration equation that relates the gauge
unit volume values for which the gauge will be used.
water content system response (the “water content count”) to
4.1.6 The objective of water content system verification is
the water mass per unit volume value of the standard on which
to evaluate the current water content calibration equation for
this response is elicited.
the gauge and determine if new calibration constants are
5.1.3 To establish the relationship between the density
required.
measured by the gauge to the soil-equivalent density of the
4.2 The density calibration equation relates the wet density
standard on which this response is elicited.
value measured by the gauge on a test site (the “independent
5.1.4 To establish the relationship between the water mass
variable”)withthedensitytestcountmeasuredbythegaugeon
per unit volume measured by the gauge to the water mass per
the test site (the “dependent variable”) and is typically expo-
unit volume of the standard on which this response is elicited.
nential or polynomial in form, with three fit coefficients.
5.1.5 To ensure that the gauge has an in-place density gauge
4.2.1 Historically, the most successful methods for comput-
precision level that is consistent with typical gauge response.
ing the density calibration equation for the density system of a
5.1.6 To ensure that the gauge has an in-place water mass
gauge is done by taking gauge density readings on three or
per unit volume gauge precision level that is consistent with
more density standards, combining the independent and depen-
typical gauge response.
dent variables into data pairs, and using a least-squares or
5.2 Gauge verification is performed for the following pur-
Newton-Raphson fitting algorithm with these data pairs to
poses:
compute the fit coefficients. These density standards have
uniquedensityvaluesthatspantherangeofdensitiesforwhich
5.2.1 To indicate to the party or agency performing the
the gauge will be used. verification when the mathematical relationship between the
4.2.2 The computation of the density calibration equation is in-place density reading indicated by the gauge and the
not necessarily limited to the process described in 4.2.1. corresponding gauge density test count needs to be adjusted so
D7759/D7759M − 21
that the gauge measurement errors do not exceed the specified 7.3 Density Reference Standard—A standard of a known
absolute maximum measurement error for the calibration in-place density value (or values) with a known uncertainty (or
method used. uncertainties) that can be used in the process of calibrating and
5.2.2 To indicate to the party or agency performing the verifying the density systems of a nuclear density/moisture
verification when the mathematical relationship between the gauge.
water mass per unit volume indicated by the gauge and the
7.4 Water Content Reference Standard—A standard of a
corresponding gauge water content test count needs to be
known in-place water mass per unit volume value (or values)
adjusted so that the gauge measurement errors do not exceed
with a known uncertainty (or uncertainties) that can be used in
the specified absolute maximum measurement error for the
the process of calibrating and verifying the water content
calibration method used.
system of a nuclear density/moisture gauge.
5.2.3 Gauge verification and calibration require specialized
7.5 Probe—A slender, elongated device, part of the gauge
training and equipment. Gauge calibration and verification are
that is inserted into the soil under measurement by the gauge.
best conducted by those trained in the proper operation of the
Thisdevicemaycontaineitheraradioactivesource,aradiation
gauge, the calibration standards, and any tables, charts, graphs,
detection device, or both. Probes containing only a radioactive
or computer programs required for the proper execution of
source are commonly referred to as “source rods.”
these operations.
NOTE 1—The quality of the result produced by this standard is
8. Hazards
dependent on the competence of the personnel performing it, and the
suitability of the equipment and facilities used. Agencies that meet the
8.1 These gauges utilize radioactive materials that may be
criteria of Practice D3740 are generally considered capable of competent
hazardous to the health of the users unless proper precautions
and objective testing/sampling/inspection/etc. Users of this standard are
are taken. Users of these gauges must become familiar with
cautioned that compliance with Practice D3740 does not in itself assure
reliable results. Reliable results depend on many factors; Practice D3740 applicable safety procedures and government regulations.
provides a means of evaluating some of those factors.
8.2 Effective user instructions, together with routine safety
6. Interferences
procedures and knowledge of and compliance with regulatory
requirements,areamandatorypartoftheoperationandstorage
6.1 Gauge calibration shall be performed in an area where
of these gauges.
the gauge being calibrated can be protected from the outside
influences of and background radiation from other nuclear
9. Density Systems Calibration, Procedure A (Curve
gauges.
Fitting Method)
6.2 Gauge calibration shall be performed in an area where
9.1 Each depth at which the nuclear gauge is able to take a
any walls surrounding or in proximity to the gauge do not
density measurement has its own independent density system,
cause reflected radiation that can be detected by the gauge.
and each of these density systems requires a distinct and
6.3 Consult Guide D7013/D7013M in its entirety to ensure
independent calibration. The methods described herein as
that the calibration area is configured properly and that the
ProcedureA, or the methods described in Procedure B, may be
interferences described in 6.1 and 6.2 can be avoided.
followed.
6.4 The accuracy and duration of gauge calibrations may be
9.2 The density systems of the gauge shall undergo the
seriously compromised if the gauge has not undergone routine
calibration method described in 4.1.1, Procedure A, after
maintenance or proper servicing prior to calibration.
manufacture and subsequently after any repairs or modifica-
tions that can affect the gauge geometry or the accuracy of the
7. Apparatus
existing calibration equation, or at the discretion of the gauge
7.1 Nuclear Density/Moisture Gauge—While exact details
owner or the calibrating agency.
of construction of the apparatus may vary, the system shall
9.2.1 The calibration of a given density system by Proce-
consist of:
dure A consists of the computation and deployment of the
7.1.1 Gamma Source—A sealed source of high-energy
mathematical formula that relates the in-place wet density
gamma radiation such as cesium or radium.
value measured by the gauge on a density standard (the
7.1.2 Gamma Detector—Any type of gamma detector such
“independent variable”) with the density test count measured
as a Geiger-Mueller tube(s).
by the gauge on a density standard (the “dependent variable”).
7.1.3 Fast Neutron Source—A sealed mixture of a radioac-
The resulting fit parameters of this formula are commonly
tive material such as americium, radium, and a target material
referredtoasthe“calibrationconstants”forthedensitysystem.
such as beryllium, or a neutron emitter such as californium-
9.2.2 The mathematical formula that is computed as the
252.
result of the calibration of a density system should be stored in
7.1.4 Slow Neutron Detector—Any type of slow neutron
the memory of the gauge, printed on tables, or shown graphi-
detector such as boron trifluoride or helium-3 proportional
cally in such a manner that the test readings acquired with the
counter.
gaugecanbeusedintheformulatocomputethecorresponding
7.2 Gauge Reference Standard—A block of material used in-place density value, either by the user or by the instrument
for checking instrument operation, correction of source decay, itself.
and to establish conditions for a reproducible reference count 9.2.3 Whereas the process used to compute the calibration
rate. constants for a gauge density systems is at the discretion of the
D7759/D7759M − 21
partyoragencyperformingthecalibration,theselectedprocess obtained by the calibrated gauge under specified conditions do
forcomputingthecalibrationconstantsshouldcomplywiththe not exceed a specified density value.
requirements of 4.2.2.
12.2 The verification for a density system of the gauge shall
9.2.4 This density system calibration may be done by the
be performed at the conclusion of either Procedure A or
gauge manufacturer, the user, or an independent vendor.
Procedure B calibrations.
12.3 The verification process for a calibration performed
10. Density Systems Calibration, Procedure B (Direct
using Procedure A may be accomplished by next performing
Comparison Method)
the calibration procedure defined in Procedure B for each
10.1 Any gauge density system that already has an estab-
density system, then computing the absolute measurement
lished calibration equation from the past performance of the
error for each comparison of the density value measured by the
calibration method ProcedureAmay undergo the Procedure B
gauge and the associated soil-equivalent density of the density
calibration procedure described herein without first repeating
standard upon which the measurement was made.
the calibration method Procedure A.
12.3.1 In the instance where the density system verification
10.2 This calibration procedure of a given density system
process follows 12.3, the maximum permissible absolute
consists of directly observing the relationship between the
measurement error for in place density measured by the gauge
in-place density value measured by the gauge on a density
on a density standard used in the calibration process typically
3 3
standard and the soil-equivalent wet density of the density
does not exceed 16 kg/m [1 lbm/ft ] of the density value
standard.
assigned to the standard. This assigned density of this standard
is based upon the density response of a typical gauge of this
10.3 Whereas the procedure (A or B) used to calibrate the
type on the standard.
gauge density system is at the discretion of the party or agency
performing the calibration, the selected calibration process
12.4 In the instance where the density system calibration is
shallcomply with the requirements of 4.1.1.1 - 4.1.1.3 or
performed using Procedure A and the verification process is
4.1.2.1 - 4.1.2.2.
performed using other empirical, historical, or statistical evalu-
ations not directly related to the empirical method described in
10.4 This density system calibration may be done by the
12.3,themaximumpermissibleabsolutemeasurementerrorfor
gauge manufacturer, the user, or an independent vendor.
inplacedensitycalculatedbythismethodonadensitystandard
3 3
typically does not exceed 16 kg⁄m [1 lbm⁄ft ] of the density
11. Density Systems Calibration, Estimated Measurement
value assigned to the standard. This assigned density of this
Uncertainties
standard is based upon the density response of a typical gauge
11.1 For any specific density system that undergoes either
of this type on the standard.
the Procedure A or Procedure B calibration method, the
uncertaintyindensitymeasurementsovertherangeofdensities 12.5 In the instance where the density system calibration
was performed using Procedure B and new calibration con-
for which gauges calibrated in this manner are used shall be
known. Uncertainties shall be known for a single maximum stants were not computed prior to this calibration, the maxi-
mum permissible absolute measurement error for in place
uncertainty value applicable to the entire density range of the
gauge, or one value from each of the following three density density calculated by this method on a density standard
3 3
typically does not exceed 32 kg⁄m [2 lbm⁄ft ] of the density
levels:
value assigned to the standard. This assigned density of this
11.1.1 At a density level within 5 % of the lower extreme of
standard is based upon the density response of a typical gauge
the density calibration range (typically 1755 kg/m [109.6
lbm/ft ]). of this type on the standard.
11.1.2 At a density level within 5 % of the mid value of the
12.6 In instances where there are more than three density
density calibration range (typically 2145 kg/m [133.9 lbm/
calibration standards used in either a ProcedureAor Procedure
ft ]).
B calibration, the permissible absolute measurement error
11.1.3 At a density level within 5 % of the upper extreme of
could exceed the values described in 12.3 through 12.5 due to
the density calibration range (typically 2612 kg/m [163.1
regression errors and/or regression residuals.
lbm/ft ]).
12.7 Failure to meet the specified measurement errors re-
NOTE 2—In 11.1, three density levels are specified as points at which
quires that the calibration constants be calculated again, so
the gauge density measurement uncertainty must be knows for the specific
Calibration Procedure A must be performed.
calibration method. Three points are used because, at a minimum, three
points define the mathematical form of the calibration equation for the
12.8 The density content system of the gauge shall undergo
density measurement system.The values of the three ranges were selected
a calibration and verification at periods not to exceed twelve
to reflect the range of the typical low density, mid density, and high
months.
density calibration standards used for the calibration of these gauges.
13. Standards Used for Density Systems Calibration
12. Density Systems Verification
12.1 The verification of the density system means that it 13.1 The density value(s) of any manufactured metallic,
fulfills specified requirements. Those specified requirements natural stone, or non-soil standard used in the calibration of the
are that the measurement errors of the wet density readings density system of the gauge shall be determined in such a
D7759/D7759M − 21
manner that the estimated standard deviation of the measure- measured by the gauge on a water content standard (the
ment results used in this determination shall not exceed 0.5 % “independent variable”) with the water content test count
of the measured standard density or densities. measured by the gauge on a water content standard (the
“dependent variable”). The resulting fit parameters of this
13.2 The density value(s) assigned to a standard that is
formula are commonly referred to as the “calibration con-
comprised of materials that have the potential to change over
stants” for the water content system.
time in density, such as soil, concrete, or solid rock, typically
need to be reestablished or verified at periods not exceeding 14.3 The mathematical formula that is computed as the
twelvemonths.Ifthestandardmaterialisshowntomaintainits result of a calibration of the water content system shall be
density within the estimated standard deviation described in stored in the memory of the gauge, printed on tables, or shown
13.1fortheenvironmentinwhichitisstoredandused,thenthe graphically in such a manner that the test readings acquired
reestablishment or verification period can be extended accord- with the gauge can be used in the formula to compute the
ingly. corresponding water mass per unit volume value, either by the
user or by the instrument itself.
13.3 The density response of a nuclear gauge is influenced
14.4 Whereas the process used to compute the calibration
by both the density of the material and the elemental compo-
constants for a gauge water content calibration system is at the
sition of the material. The contribution of the elemental
discretionofthepartyoragencyperformingthecalibration,the
composition of the material to the density response of the
selected process for computing the calibration constants shall
gauge must be taken into consideration when establishing the
comply with the requirements of 4.3.1.
density value of a density standard.
14.5 The water content system calibration may be done by
NOTE 3—Different nuclear density calibration techniques often utilize
different nuclear physics principles to determine how the elemental the gauge manufacturer, the user, or an independent vendor.
composition of the material influences the density response of the
instrument. As a result, there may be a statistically significant bias
15. Water Content System Calibration, Procedure B
between the density values read between gauges that are calibrated using
different density calibration techniques. Consequently, gauge users who 15.1 Any gauge water content system that already has an
take measurements with gauges calibrated using different density calibra-
established calibration equation from the past performance of
tion techniques may need to adjust measurement results to compensate for
the calibration method described in Procedure A may undergo
this bias.
theProcedureBcalibrationproceduredescribedhereinwithout
13.4 If the density standard is a solid block of material, the
firstrepeatingthecalibrationmethoddescribedinProcedureA.
physical dimensions of the density standard shall be sufficient
15.2 This calibration procedure of the gauge water content
in size so that the count rate of the gauge used to read the
system consists of observing the relationship between the
standard will not change if the standard is enlarged in any
inplace water mass per unit volume value measured by the
dimension. Otherwise, follow the block manufacturer’s recom-
gauge on a water content standard and the water mass per unit
mendations; lateral abutting plates or other density standards
volume value of the water content standard.
may be positioned so that the count rate will not be affected.
15.3 Whereas the procedure (A or B) used to calibrate the
NOTE 4—For density standards that are solid blocks of material,
gauge water content system is at the discretion of the party or
minimum surface dimensions of approximately 610 by 430 mm [24 by
agency performing the calibration, the calibration process shall
17 in.] have proven satisfactory. For the backscatter method a minimum
depth of 230 mm [9 in.] is adequate; while for the direct transmission comply with the requirements of 4.1.4.1 - 4.1.4.3 or
method the depth shall be at least 50 mm [2 in.] deeper than the deepest
4.1.5.1 - 4.1.5.2.
rod penetration depth. A larger surface area may be necessary for the
15.4 The water content system calibration and verification
backscatter/air-gapmethod.Forblockswithwidthsorlengthssmallerthan
the sizes specified, follow the block manufacturer’s recommendations for may be done by the gauge manufacturer, the user, or an
proper installation and use.
independent vendor.
The most successful standards that have been established for density
system calibration and verification have been blocks made of magnesium,
16. Water Content System Calibration, Estimated
aluminum, aluminum/magnesium, granite, and limestone. These blocks
Measurement Uncertainty
have been used in combination with each other, with historical equation
information, and with other prepared block(s) to produce accurate and
16.1 Foranyspecificwatermassperunitvolumecalibration
reliable density system adjustments and calibrations.
process, the uncertainty in water mass per unit volume mea-
surements over the range of water mass per unit volume values
14. Water Content System Calibration, Procedure A
for which gauges calibrated in this manner are used shall be
(Curve Fitting Method)
known. Uncertainties shall be known for, at a minimum, a
3 3
14.1 The water content system of the gauge shall undergo
watermassperunitvolumelevelwithin32 kg⁄m [2.0 lbm⁄ft ]
the calibration method described in 4.1.4 initially after manu-
of the upper extreme of the water mass per unit volume
3 3
facture and subsequently after any repairs or modifications that
calibration range (typically 300 kg⁄m [18.7 lbm⁄ft]or
can affect the gauge geometry or the accuracy of the existing
higher).
calibration equation.
17. Water Content System Verification
14.2 This calibration of a water content system consists of
the computation of and deployment of the mathematical 17.1 The verification of the gauge water content system
formula that relates the water mass per unit volume value means that it fulfills specified requirements. Those specified
D7759/D7759M − 21
requirementsarethatthemeasurementerrorsofthewatermass rate of the gauge used to read the standard will not change if
per unit volume readings obtained by the calibrated gauge the standard is enlarged in any dimension. Otherwise, follow
under specified conditions do not exceed a specified water block manufacturers recommendations; lateral abutting plates
mass per unit volume value. or density standards may be positioned so that the count rate
will not be affected.
17.2 The verification for the water content system of the
gauge shall be performed at the conclusion of either Procedure
NOTE 5—For water content standards that are solid blocks of material,
A or Procedure B calibrations. minimum surface dimensions of approximately 610 mm long by 460 mm
wide by 200 mm deep [approximately 24 in. by 18 in. by 8 in.] have
17.3 The verification process for a calibration performed
proven satisfactory. For blocks with width or length smaller than the sizes
using Procedure A may be accomplished by next performing
specified, follow the block manufacturer’s recommendation for proper
installation and use.
the calibration procedure defined in Procedure B for the gauge,
The most successful high water content standards that have been
then computing the absolute measurement error for each
establishedforwatercontentsystemcalibrationandverificationhavebeen
comparison of the water mass per unit volume value measured
blocks made of alternating sheets of magnesium and polyethylene or
by the gauge and the associated water mass per unit value of
alternating sheets of aluminum and polyethylene. The most successful
the water content standard upon which the measurement was
zero water content standards that have been established for water content
system calibration and verification have been the metallic density stan-
made.
dards used for calibration and verification of the density calibration
17.4 The verification process for a calibration performed
system, such as magnesium and aluminum (see Note 4). These blocks
using Procedure A may consist of using other empirical, have been used in combination with each other, with historical equation
information, and with other prepared block(s) to produce accurate and
historical, or statistical evaluations not directly related to the
reliable density system adjustments and calibrations.
empirical method described 17.3.
18.2 Establishing the Water Mass Per Unit Volume Values of
17.5 The maximum permissible measurement error for wa-
Water Content Calibration Standards:
ter mass per unit volume measured by the gauge on a water
18.2.1 Typically, the water content standards used in the
content standard typically does not exceed 5 % of the water
water content system calibration of nuclear gauges do not
mass per unit volume value assigned to the standard. This
contain any water. Instead, they are homogenous blocks
assigned water mass per unit volume value of this standard is
containing hydrogen-bearing (hydrogenous) materials that
based upon the water content response of a typical gauge of
thermalize the neutrons emitted by the gauge in a similar
this type on the standard. However, the 5 % measurement error
manner to the hydrogen in water. Consequently, these stan-
limit does not apply for intrinsic moisture standards used as
dardstypicallyhavewatermassperunitvolumevalueassigned
zero water mass per unit volume standards, since in this case a
to them by either (a) comparing gauge response on them to
percentage-based error limit on a zero value standard has no
gauge response on soil with a known water mass per unit
significance. The maximum permissible measurement error for
volumevalue,or(b)calculatingandusingthewater-equivalent
water mass per unit volume measured by the gauge on a zero
hydrogen density of the block.
water mass per unit volume standard typically does not exceed
3 3
18.2.2 To determine the water mass per unit volume value
16 kg⁄m [1 lbf⁄ft ].
of a standard, the following method may be used:
17.6 The water content system of the gauge shall undergo a
18.2.2.1 Prepare containers of compacted material with a
calibration and verification at periods not to exceed twelve
water content determined by oven dry (Test Method D2216)
months.
and an in-place density calculated from either the mass of the
materialandtheinsidedimensionsofthecontainer,orfromthe
18. Standards Used for Water Content System
mass of specimen(s) of known volume sampled from the
Calibration
material.Thewatermassperunitvolumeofthematerialinthis
18.1 Properties and Calibration Intervals of the Standards:
container may be calculated as follows:
18.1.1 The water mass per unit volume value(s) of any
ρ 3 w
standard used in gauge water content system calibration shall
ρ 5 (1)
wm
1001w
have its water mass per unit volume value(s) measured and
established upon manufacture. After this initial establishment
where:
of the water mass per unit volume value(s), the standard shall
3 3
ρ = water mass per unit volume, kg/m or lbm/ft ,
wm
be calibrated at a period established by the manufacturer. If the
w = water content, percent of dry mass, and
calibrationrevealsthatthewatermassperunitvolumevalue(s)
3 3
ρ = in-place (wet) density, kg/m or lbm/ft .
has/have changed, then the new water mass per unit volume
18.2.2.2 Measure the container(s) described in18.2.2.1 with
value(s) of the standard shall be determined.
a nuclear gauge, and formulate the mathematical relationship
18.1.2 The water mass per unit volume value(s) assigned to
between the water mass per unit volume values of the
a standard that is comprised of materials that have the potential
material(s) and the corresponding gauge moisture count re-
to change over time in water content, such as soil, concrete, or
sponse.
solid rock, shall be reestablished or verified at periods not
exceeding twelve months. 18.2.2.3 Measure the standard with the nuclear gauge, and
18.1.3 If the water content standard is a solid block of use the mathematical relationship in Eq 1 to determine the
material, the physical dimensions of the water content standard water mass per unit volume (and its uncertainty) for the
shall be sufficient in size so that the water content system count standard.
D7759/D7759M − 21
18.2.3 Alternatively, the water mass per unit volume value readings. Calculate the standard deviation of the resulting
(and its uncertainty) for a standard may be calculated based readings. This is the gauge precision
upon the known hydrogen density of the standard and the
19.3 Using the procedure described in either
elemental composition of the standard.
19.2.1 or 19.2.2, ensure a gauge count precision of at least
18.2.4 The water content system of a nuclear gauge is not
one-half the gauge count precision required for field use,
only affected by the water contained in the material under
assuming field use measurement of one-minute duration.
measure, but also, to a lesser extent, by the elemental compo-
sition of the material being measured. Consequently, the water
20. Report: Test Data Sheet(s)/Form(s)
mass per unit volume values measured by the gauge may not
20.1 The methodology used to specify how data are re-
correspond, to the desired level of accuracy, with the water
corded on the test data sheet(s)/form(s)/file(s), as given below,
mass per unit volume value of some materials being measured.
is covered in 1.9 and in Practice D6026.
The gauge calibration shall be accurate for silica and water;
however, for other materials the water content system may
20.2 Data for nuclear surface moisture and density gauge
require adjustment to achieve the desired level of calibration
calibration equation calculation are typically collected and
accuracy.
recorded electronically, whereas data for the calibration pro-
cess where density values are collected rather than counts are
NOTE6—Becauseofthedifferentapproachesofthedifferentacceptable
typically collected manually.
methodsofassignmentofwatermassperunitvolumevaluestocalibration
standards, there may be a statistically significant bias between the water
20.3 When a density system calibration as described in
massperunitvolumevaluesreadbetweengaugesthatarecalibratedusing
Procedure B is performed on a gauge, record as a minimum the
different water mass per unit volume calibration techniques.
Consequently, gauge users who take measurements with gauges calibrated following general information (data):
using different water mass per unit volume calibration techniques may
20.3.1 The model and serial number of the gauge, or any
need to adjust measurement results to compensate for this bias.
other information that uniquely identifies the gauge.
20.3.2 The date when the calibration is performed.
19. Gauge Precision
20.3.3 The density reference standard count at the time that
19.1 Gauge precision is defined as the change in density or
the density calibration and verification are performed.
water mass per unit volume that occurs corresponding to a one
20.3.4 For each density standard used in the calibration, the
standarddeviationchangeinthecountduetotherandomdecay
wet density value measured by the gauge.
of the radioactive source. The density of the material and time
20.3.5 A signature and title, or an equivalent identification
period of the count must be stated. It is important to note that
of the person(s) responsible for the content of the recorded
“gauge precision” is not the same as the precision and bias of
data.
the test method described in D6938 and Research Report RR
20.3.6 The aforementioned information for each of the
D18-1004.
source rod positions of the gauge shall be included in the same
sheet(s)/form(s)/file(s).
19.2 Calculate the gauge precision using the methods in
either 19.2.1 or 19.2.2. For in-place density, use a material
20.4 When a density system calibration as described in
3 3
having a d
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7759/D7759M − 14 D7759/D7759M − 21
Standard Guide for
Nuclear Surface Moisture and Density Gauge Calibration
This standard is issued under the fixed designation D7759/D7759M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 Procedure A—This guide describes the process and objective of formulating the mathematical relationship between the density
system count of a nuclear surface moisture and density gauge and the corresponding wet density value of the density standard upon
which the density system response was observed.
1.2 Procedure B—This guide describes the process and objective of calibratingcomparing the wet density system ofmeasured by
a nuclear surface moisture and density gauge, or formulating the mathematical relationship between the density system response
(the “density count”) of a nuclear surface moisture and density gauge and the corresponding density value of the density standard
upon which the density system response was observed.
1.3 This guide describes the process and objective of the verification of the measurements of a nuclear surface moisture and
density gauge.
1.4 Procedure A—This guide describes the process and objective of calibrating the water content system of a nuclear surface
moisture and density gauge, or formulating the mathematical relationship between the water content system response (the “water
content count”) count of a nuclear surface moisture and density gauge and the corresponding water mass per unit volume value
of the water content standard upon which the water content system response was observed.
1.5 Procedure B—This guide describes the process and objective of verifying the density system of comparing the water mass per
unit volume measured by a nuclear surface moisture and density gauge.gauge and the corresponding water mass per unit volume
of the corresponding water content standard upon which the water content system response was observed.
1.6 This guide describes the process and objective of verifying the water content system of the verification of the measurements
of a nuclear surface moisture and density gauge.
1.7 This guide describes two mathematical processes by which the gauge measurement precision may be computed or measured.
1.8 This guide offers guidance for developing and reporting estimates of uncertainties in measurements made with gauges that
have undergone calibration orand verification.
1.9 All observed and calculated values shall confirmconform to the guide for significant digits and rounding established in Practice
D6026.
This practice is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.08 on Special and Construction
Control Tests.
Current edition approved June 1, 2014May 1, 2021. Published July 2014June 2021. Originally approved in 2012. Last previous edition approved in 20122014 as
D7759–12a.–14. DOI: 10.1520/D7759-14.10.1520/D7759-21.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7759/D7759M − 21
1.10 Units—The values stated in either SI units or inch pound inch-pound units are to be regarded separately as standard. The
values stated in each system mayare not benecessarily exact equivalents; therefore, to ensure conformance with the standard, each
system shall be used independently of the other. Combiningother, and values from the two systems may result in non-conformance
with the standard.shall not be combined. Within the text of this standard, SI units appear first followed by the inch-pound (or other
non-SI) units in brackets.
1.10.1 Reporting of test results in units other than SI shall not be regarded as nonconformance with this guide.
1.11 This guidestandard does not purport to address all of the safety concerns, if any, associated with its use. It is the
responsibility of the user of this guidestandard to establish appropriate safety safety, health, and healthenvironmental practices and
determine the applicability of regulatory limitations prior to use.
1.12 This guide offers an organized collection of information or a series of options and does not recommend specific course of
action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not
all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the
standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied
without consideration of a project’s many unique aspects. The word “Standard” in the title of this document means only that the
document has been approved through the ASTM consensus process.
1.13 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D6026 Practice for Using Significant Digits in Geotechnical Data
D6938 Test Methods for In-Place Density and Water Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
D7013D7013/D7013M Guide for Calibration Facility Setup for Nuclear Surface Gauges
D8167/D8167M Test Method for In-Place Bulk Density of Soil and Soil-Aggregate by a Low-Activity Nuclear Method (Shallow
Depth)
3. Terminology
3.1 Definitions—See Terminology D653 for general definitions. For definitions of common metrology terms used in this standard,
refer to the VIM—International Vocabulary of Metrology.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 coverage factordensity system, calibration, n—a number larger than one by which a combined standard measurement
uncertainty is multiplied to obtain an expanded measurement uncertainty.set of processes by which, for each density standard used
in the process, a density indication (gauge count or gauge density response) is obtained by the nuclear gauge on the density
standard, and a relationship is established between the indications of the gauge and the density of the standard; the uncertainty of
the standard and the indication must be established.
3.2.2 definitional uncertainty , n—the component of measurement uncertainty resulting from the finite amount of detail in the
definition of the measurand. The “measurand” in the case of a nuclear surface moisture density gauge, is typically either in-place
density or water mass per unit volume.
3.2.2 density system calibration,calibration equation, n—the method by which the values of the fit parameters in the equation
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
JCGM 200:2008: International Vocabulary of Metrology—Basic and General Concepts and Associated Terms (VIM). 2008: Joint Document Committee for Guides in
Metrology.International vocabulary of metrology—Basic and general concepts and associated terms (VIM), 3rd Edition. Joint Committee for Guides in Metrology, 2012.
https://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2012.pdf
D7759/D7759M − 21
mathematical function that relates the density system response (the “density count”) of a nuclear gauge and the corresponding
density value of the density standard upon which that density system response was observed are computed. In addition, the
uncertainty of measurements taken with gauges calibrated by the specific method must be known at representative density values
that span the range of densities for which the calibration is valid.of the medium under measurement by the gauge (the independent
variable) to the density system count response of the gauge (the dependent variable).
3.2.3 density system verification, n—a set of operations or processes, or both, by which, for each density standard used in the
process, the in-place density value(s) measured by the nuclear gauge on the density standard is related to the corresponding value(s)
of the standard or standards. In addition, the uncertainty of measurements taken with gauges that meets the established verification
criterion or criteria must be known at representative densities that span the range of densities for which the verification is
valid.processes by which the acceptability of the associated density calibration equation of a gauge is determined.
3.2.5 detector, n—a device to detect and measure radiation.
3.2.6 expanded measurement uncertainty , n—product of a combined standard measurement uncertainty and a coverage factor
larger than one.
3.2.7 gamma (radiation) source, n—a sealed source of radioactive material that emits gamma radiation as it decays.
3.2.8 in-place density, n—the total mass (solids plus water) per total volume of soil or soil-aggregates measured in place.
3.2.9 measurement uncertainty , n—non-negative parameter characterizing the dispersion of the quantity values being attributed
to a measurand. The “measurand” in the case of a nuclear surface moisture density gauge, is typically either in-place density or
water mass per unit volume.
3.2.10 neutron (radiation) source, n—a sealed source of radioactive material that emits neutron radiation as it decays.
3.2.4 nuclear gauge, n—a device containing one or more radioactive sources used to measure certain properties of soil and
soil-aggregates.
3.2.5 prepared standards, n—density or water content measurement standards prepared of soil, solid rock, concrete, and
engineered materials, that have density or water content values, or both, that are established and known to a specified uncertainty.
3.2.6 standard measurement uncertaintysoil-equivalent density, , n—measurement uncertainty expressed as a standard deviation.
the density of an average soil (where an “average soil” is defined herein to have a Z/A value of 0.5) that yields the same gauge
density count response as a metallic calibration standard; Z is the average atomic number of a material and A is the average atomic
mass number of that same material.
3.2.14 test count, N, n—the measured output of a detector for a specific type of radiation for a given test.
3.2.15 Type A Uncertainty Evaluation , n—evaluation of a component of measurement uncertainty by a statistical analysis of
measured quantity values obtained under defined measurement conditions.
3.2.16 Type B Uncertainty Evaluation , n—evaluation of a component of measurement uncertainty by means other than a Type
A Evaluation.
3.2.17 volumetric water content, n—the volume of water as a percent of the total volume of soil or rock material.
3.2.18 water content, n—the ratio of the mass of water contained in the pore spaces of soil or soil-aggregate, to the solid mass
of particles in that material, expressed as a percentage (this is sometimes referred to in some scientific fields as gravimetric water
content to differentiate it from volumetric water content).
3.2.7 water content system calibration, n—the method by which the values of the fit parameters in the equation that relates the
water content system response (the “water content count”) of a nuclear a set of processes by which, for each water content standard
D7759/D7759M − 21
used in the process, a water mass per unit volume indication (gauge count or water mass per unit volume value) is obtained by
the nuclear gauge on the water content standard, and a relationship is established between the indication of the gauge and the
corresponding water mass per unit volume value of the water content standard upon which that water content system response was
observed are computed. In addition, standard; the uncertainty of measurements taken with the gauges calibrated by the specific
method must be known at representative water mass per unit volume values that span the range of water mass per unit volume
values for which the calibration is valid.the standard and the indications must be established.
3.2.8 water mass per unit volume calibration equation, n—the mathematical function that relates the water mass per unit volume
of the medium under measurement by the gauge (the independent variable) to the water content system count response of the gauge
(the dependent variable).
3.2.9 water content system verification, n—a set of operations or processes, or both, by which, for each water content standard used
in the process, the in-place water mass per unit volume value(s) measured by the nuclear gauge on water content standard is related
to the corresponding value(s) of these standards. In addition, the uncertainty of measurements taken with gauges that meets the
established verification criterion or criteria must be known at representative processes by which the acceptability of the water mass
per unit volume values that span the range of water mass per unit volume values for which the verification is valid.calibration
equation of a gauge is determined.
3.2.21 water mass per unit volume, n—the ratio of the mass of water contained in the pore spaces of a soil or soil-aggregate to
the total volume occupied by that soil or rock material.
4. Summary of Practice
4.1 The objectivessummary of the practice areis as follows:
4.1.1 Procedure A—The objective of For new gauges and gauges that fail to meet the required density system calibrationverifi-
cation is to formulate a mathematical equation, orcriteria, for each affected index rod position density calibration equation,one must
perform thata density calibration in which one relates the gauge density system response (the “density count”)gauge counts) to
the soil-equivalent density of the standardstandard(s) on which this response is elicited. The maximum uncertainties of subsequent
gauge density readings shall be determined forthe response is elicited and, in a second step, uses this information to establish a
the calibration process equation.that is used. The standards used for the determination of uncertainty shall be representative of
the range of densities for which the gauge will be used.
4.1.1.1 The measurement uncertainties of the density standard(s) and the gauge density system counts must be known.
4.1.1.2 The standard(s) used for the determination of uncertainty shall be representative of the range of densities for which the
gauge will be used.
4.1.1.3 The mode of density calibration just described is not limited to new gauges or gauges that fail to meet the required density
system verification criteria.
4.1.2 Procedure B—For gauge index rod positions for which a density calibration equation has been formulated, one has the option
of performing a density calibration in which one establishes the relation between the soil-equivalent density values of the
necessary number of soil-equivalent density standard(s) and the corresponding soil-equivalent density measured by the gauge when
used to measure the standards and, in a second step, uses this information to establish the relationship between these two density
values.
4.1.2.1 The measurement uncertainties of the density standards and the density measured by the gauge must be known.
4.1.2.2 The standard(s) used for the determination of uncertainty shall be representative of the range of densities for which the
gauge will be used.
4.1.3 The objective of density system verification is to evaluate the current density calibration equation for the gauge and
determine if new calibration constants are required.
4.1.4 Procedure A—The objective of density system For new gauges and gauges that fail to meet the required water content system
verification criteria, one must perform a verificationwater content calibration is to evaluate the current density calibration
equation for the gauge and determine if a new calibration is required. The verification method will be based upon relating, at the
D7759/D7759M − 21
pertinent density or densities for the specific method, the density value of a known density standard to the density measured by
the gauge. The maximum uncertainties of subsequent gauge density readings shall be determined for the verification method used.
The standards used for the determination of uncertainty shall be representative of the range of densities for whichin which one
establishes the relation between the water mass per unit volume of the necessary number of water content standard(s) and the
corresponding water system gauge counts elicited from the gauge when used to measure these standards and, in a second step, uses
this information to establish a the gauge calibration equation.will be used.
4.1.4.1 The measurement uncertainties of the water content standard(s) and the gauge counts must be known.
4.1.4.2 The standard(s) used for the determination of uncertainty shall be representative of the range of water mass per unit volume
for which the gauge will be used.
4.1.4.3 The mode of water content system calibration just described is not limited to new gauges or gauges that fail to meet the
required water content system verification criteria.
4.1.5 Procedure B—The objective of water content systemFor gauges for which the calibration constants of a water mass per unit
volume calibration is to formulate a mathematical equation, or equation have been formulated, one may perform a water content
calibration equation, that relates the gauge water content system response (the “water content count”) to in which one establishes
the relation between the water mass per unit volume value of the standard on which this response is elicited. The uncertainties of
subsequent gauge water mass per unit volume readings shall be known for, at a minimum, a necessary number of water content
3 3
standard(s) and the corresponding water mass per unit volume level within 32 kg/mmeasured by [2.0 lbm/ft ] of the upper
extreme of the the gauge when used to measure these standard(s) and, in a second step, uses this information to establish the
3 3
relationship between these two water mass per unit volume calibration range (typically 300 kg/mvalues. [18.7 lbm/ft ] or higher).
4.1.5.1 The measurement uncertainties of the water content standards and the water mass per unit volume measured by the gauge
must be known.
4.1.5.2 The standards used for the determination of uncertainty shall be representative of the range of water mass per unit volume
values for which the gauge will be used.
4.1.6 The objective of water content system verification is to evaluate the current water content system calibration equation for
the gauge and determine if a new calibration is required. This evaluation will be based upon relating, at the pertinent water mass
per unit volume values for the specific method, the water mass per unit volume value of a known water mass per unit volume
standard to the water mass per unit volume value measured by the gauge. The uncertainties of subsequent gauge water mass per
unit volume readings shall be known for, at a minimum, a water mass per unit volume level within 32 kg/mnew calibration
3 3 3
constants are required. [2.0 lbm/ft ] of the upper extreme of the water mass per unit volume calibration range (typically 300 kg/m
[18.7 lbm/ft ] or higher).
4.1.5 The density calibration equation relates the in-place density value measured by the gauge on a test site (the “independent
variable”) with the density test count measured by the gauge on the test site (the “dependent variable”) is typically exponential
or polynomial in form, with three fit coefficients.
4.2 Historically, the most successful methods for calibrating the density system of a gauge is done by taking gauge density
readings on three or more density standards, combining the independent and dependent variables into data pairs, and using a
least-squares or Newton-Rafson fitting algorithm with these data pairs to compute the fit coefficients. These density standards have
unique density values that span the range of densities for which the gauge will be used.The density calibration equation relates the
wet density value measured by the gauge on a test site (the “independent variable”) with the density test count measured by the
gauge on the test site (the “dependent variable”) and is typically exponential or polynomial in form, with three fit coefficients.
4.2.1 The density system calibration Historically, the most successful methods for computing the density calibration equation for
the density system of a gauge is not necessarily limited to the process described indone by taking gauge density readings on three
or more density standards, combining the independent and dependent 4.2. However, for any method that is used in the density
system calibration process, one must know the uncertainties of the in-place density readings measured by devices calibrated in this
manner over variables into data pairs, and using a least-squares or Newton-Raphson fitting algorithm with these data pairs to
compute the fit coefficients. These density standards have unique density values that span the range of density values densities for
which the gauge will be used.
4.2.2 For The computation of the density calibration equation is not necessarily limited to the process described in 4.2.1. However,
D7759/D7759M − 21
for any method that is used in the density system verificationcalibration process, one must know the uncertainties of the in-placewet
density readings measured by devices calibrated in this manner over the range of density values for which the gauge will be used.
4.2.3 The water content calibration equation that relates the in-place water mass per unit volume value measured by the gauge on
a test site (the “independent variable”) with the water content mass per unit volume test count measured by the gauge on the test
site (the “dependent variable”) is typically linear in form, with two fit coefficients.
4.3 Historically, the most successful method for calibratingcomputing the water content system calibration equation of a gauge is
by taking readings on two water content standards (one of which is a zero water content standard), combining the independent and
dependent variables into data pairs, and using a least-squares or fitting algorithm with these data pairs to compute computing the
fit coefficients.
4.3.1 The computation of the water content system calibration of a gauge calibration equation is not necessarily limited to the
process described in 4.3. However, for any method that is used in the water content system calibration process, one must know
the uncertainties of the water mass per unit volume readings measured by devices calibrated in this manner over the range of water
mass per unit volume values for which the gauge will be used.
4.3.2 For any method that is used in the water content system verification process, one must know the uncertainties of the water
mass per unit volume readings measured by devices calibrated in this manner over the range of mass per unit volume values for
which the gauge will be used.
4.4 See Appendix X1 for a flowchart of the calibration and verification processes.
5. Significance and Use
5.1 Gauge calibration is performed for the following purposes:
5.1.1 To formulate a mathematical equation, or density calibration equation,When necessary, to compute the calibration constants
of a density calibration equation that relates the gauge density system response (the “density count”) to the soil-equivalent density
of the standard on which this response is elicited.
5.1.2 To formulate a mathematical equation, or When necessary, to compute the calibration constants of a water content calibration
equation,equation that relates the gauge water content system response (the “water content count”) to the water mass per unit
volume value of the standard on which this response is elicited.
5.1.3 To establish the relationship between the density measured by the gauge to the soil-equivalent density of the standard on
which this response is elicited.
5.1.4 To establish the relationship between the water mass per unit volume measured by the gauge to the water mass per unit
volume of the standard on which this response is elicited.
5.1.5 To ensure that the gauge has an in-place density gauge precision level that is consistent with typical gauge response.
5.1.6 To ensure that the gauge has an in-place water mass per unit volume gauge precision level that is consistent with typical
gauge response.
5.2 Gauge verification is performed for the following purposes:
5.2.1 To indicate to the party or agency performing the verification when the mathematical relationship between the in-place
density reading indicated by the gauge and the corresponding gauge density test count needs to be adjusted so that the gauge
calibration meets the required level of measurement uncertainty.measurement errors do not exceed the specified absolute maximum
measurement error for the calibration method used.
5.2.2 To indicate to the party or agency performing the verification when the mathematical relationship between the water mass
per unit volume indicated by the gauge and the corresponding gauge water content test count needs to be adjusted so that the gauge
calibration meets the required level of measurement uncertainty.measurement errors do not exceed the specified absolute maximum
measurement error for the calibration method used.
D7759/D7759M − 21
5.2.3 Gauge verification and calibration require specialized training and equipment. Gauge calibration and verification should only
be are best conducted by those trained in the proper operation of the gauge, the calibration or verification standards, and any tables,
charts, graphs, or computer programs required for the proper execution of these operations.
NOTE 1—The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the
equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective
testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable
results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
6. Interferences
6.1 Gauge calibration and verification should shall be performed in an area where the gauge being calibrated can be protected from
the outside influences of and background radiation from other nuclear gauges.
6.2 Gauge calibration and verification should shall be performed in an area where any walls surrounding or in close proximity to
the gauge do not cause reflected radiation that can be detected by the gauge.
6.3 Consult Guide D7013D7013/D7013M should be consulted in its entirety to ensure that the calibration area is configured
properly and that the interferences described in 6.1 and 6.2 can be avoided.
6.4 The accuracy and duration of gauge calibrations or verifications may be seriously compromised if the gauge has not undergone
routine maintenance or proper servicing prior to calibration or verification.calibration.
7. Apparatus
7.1 Nuclear Density/Moisture Gauge—While exact details of construction of the apparatus may vary, the system shall consist of:
7.1.1 Gamma Source—A sealed source of high-energy gamma radiation such as cesium or radium.
7.1.2 Gamma Detector—Any type of gamma detector such as a Geiger-Mueller tube(s).
7.1.3 Fast Neutron Source—A sealed mixture of a radioactive material such as americium, radium, and a target material such as
beryllium, or a neutron emitter such as californium-252.
7.1.4 Slow Neutron Detector—Any type of slow neutron detector such as boron trifluoride or helium-3 proportional counter.
7.2 Gauge Reference Standard—A block of material used for checking instrument operation, correction of source decay, and to
establish conditions for a reproducible reference count rate.
7.3 Density Reference Standard—A standard of a known in-place density value (or values) with a known uncertainty (or
uncertainties) that can be used in the process of calibrating orand verifying the density systems of a nuclear density/moisture gauge.
7.4 Water Content Reference Standard—A standard of a known in-place water mass per unit volume value (or values) with a
known uncertainty (or uncertainties) that can be used in the process of calibrating orand verifying the water content system of a
nuclear density/moisture gauge.
7.5 Probe—A slender, elongated device, part of the gauge that is inserted into the soil under measurement by the gauge. This
device may contain either a radioactive source, a radiation detection device, or both. Probes containing only a radioactive source
are commonly referred to as “source rods.”
8. Hazards
8.1 These gauges utilize radioactive materials that may be hazardous to the health of the users unless proper precautions are taken.
Users of these gauges must become familiar with applicable safety procedures and government regulations.
D7759/D7759M − 21
8.2 Effective user instructions, together with routine safety procedures and knowledge of and compliance with Regulatory
Requirements,regulatory requirements, are a mandatory part of the operation and storage of these gauges.
9. Density Systems CalibrationCalibration, Procedure A (Curve Fitting Method)
9.1 The density systems of the gauge shall undergo a calibration initially after manufacture and subsequently after any repairs or
modifications that can affect the gauge geometry or the accuracy of the existing calibration curve.
9.1 Each depth at which the nuclear gauge is able to take a density measurement has its own independent density system, and each
of these density systems requires a distinct calibration initially after manufacture and subsequently after any repairs or
modifications that can affect the gauge geometry or the accuracy of the existing calibration curve.and independent calibration. The
methods described herein as Procedure A, or the methods described in Procedure B, may be followed.
9.2 The calibration of a given density system consists of the computation density systems of the gauge shall undergo the
calibration method described in 4.1.1and deployment of the mathematical formula that relates the in-place density value measured
by the gauge on a density standard (the “independent variable”) with the density test count measured by the gauge on a density
standard (the “dependent variable”). The resulting fit parameters of this formula are commonly referred to as the “calibration
constants” for the density system., Procedure A, after manufacture and subsequently after any repairs or modifications that can
affect the gauge geometry or the accuracy of the existing calibration equation, or at the discretion of the gauge owner or the
calibrating agency.
9.2.1 The calibration of a given density system by Procedure A consists of the computation and deployment of the mathematical
formula that relates the in-place wet density value measured by the gauge on a density standard (the “independent variable”) with
the density test count measured by the gauge on a density standard (the “dependent variable”). The resulting fit parameters of this
formula are commonly referred to as the “calibration constants” for the density system.
9.2.2 The mathematical formula that is computed as the result of the calibration of a density system should be stored in the
memory of the gauge, printed on tables, or shown graphically in such a manner that the test readings acquired with the gauge can
be used in the formula to compute the corresponding in-place density value, either by the user or by the instrument itself.
9.2.3 Whereas the process used to compute the calibration constants for a gauge density systems is at the discretion of the party
or agency performing the calibration, the selected process for computing the calibration constants should comply with the
requirements of 4.2.2.
9.2.4 This density system calibration may be done by the gauge manufacturer, the user, or an independent vendor.
9.4 The mathematical formula that is computed as the result of the calibration of a density system should be stored in the memory
of the gauge, printed on tables, or shown graphically in such a manner that the test readings acquired with the gauge can be used
in the formula to compute the corresponding in-place density value, either by the user or by the instrument itself.
9.5 The method and test procedure used in collecting the density test count data to be used in the density calibration constant
formulation shall be the same as those used for obtaining the field test count data.
9.6 The density system calibration may be done by the gauge manufacturer, the user, or an independent vendor.
9.7 Whereas the process used to calibrate the gauge density systems is at the discretion of the party or agency performing the
calibration, the calibration process should comply with the requirements of 4.2.1.
9.8 For a density system that has just completed a density system calibration, the maximum permissible measurement error for
3 3
in place density measured by the gauge on a density standard used in the calibration typically does not exceed 16 kg/m [1 lbm/ft ]
of the density value assigned to the standard. This assigned density of this standard is based upon the density response of a typical
gauge of this type on the standard.
9.9 For any specific density system calibration process, the uncertainty in density measurements over the range of densities for
D7759/D7759M − 21
which gauges calibrated in this manner are used shall be known. Uncertainties shall be known for a single maximum uncertainty
value applicable to the entire density range of the gauge, or, at a minimum, one value from each of the following three density
levels:
3 3
9.9.1 At a density level within 5 % of the lower extreme of the density calibration range (typically 1755 kg/m [109.6 lbm/ft ]).
3 3
9.9.2 At a density level within 5 % of the mid value of the density calibration range (typically 2145 kg/m [133.9 lbm/ft ]).
3 3
9.9.3 At a density level within 5 % of the upper extreme of the density calibration range (typically 2612 kg/m [163.1 lbm/ft ]).
9.10 Using the procedure described in either 15.1.1 or 15.1.2, ensure a gauge count precision of at least one-half the gauge count
precision required for field use, assuming field use measurement of one-minute duration.
9.11 The density system of the gauge shall undergo a calibration or a verification at periods not to exceed twelve months.
10. Density Systems Calibration, Procedure B (Direct Comparison Method)
10.1 Any gauge density system that already has an established calibration equation from the past performance of the calibration
method Procedure A may undergo the Procedure B calibration procedure described herein without first repeating the calibration
method Procedure A.
10.2 This calibration procedure of a given density system consists of directly observing the relationship between the in-place
density value measured by the gauge on a density standard and the soil-equivalent wet density of the density standard.
10.3 Whereas the procedure (A or B) used to calibrate the gauge density system is at the discretion of the party or agency
performing the calibration, the selected calibration process shallcomply with the requirements of 4.1.1.1 - 4.1.1.3 or
4.1.2.1 - 4.1.2.2.
10.4 This density system calibration may be done by the gauge manufacturer, the user, or an independent vendor.
11. Density Systems Calibration, Estimated Measurement Uncertainties
11.1 For any specific density system that undergoes either the Procedure A or Procedure B calibration method, the uncertainty in
density measurements over the range of densities for which gauges calibrated in this manner are used shall be known. Uncertainties
shall be known for a single maximum uncertainty value applicable to the entire density range of the gauge, or one value from each
of the following three density levels:
3 3
11.1.1 At a density level within 5 % of the lower extreme of the density calibration range (typically 1755 kg/m [109.6 lbm/ft ]).
3 3
11.1.2 At a density level within 5 % of the mid value of the density calibration range (typically 2145 kg/m [133.9 lbm/ft ]).
3 3
11.1.3 At a density level within 5 % of the upper extreme of the density calibration range (typically 2612 kg/m [163.1 lbm/ft ]).
NOTE 2—In 11.1, three density levels are specified as points at which the gauge density measurement uncertainty must be knows for the specific calibration
method. Three points are used because, at a minimum, three points define the mathematical form of the calibration equation for the density measurement
system. The values of the three ranges were selected to reflect the range of the typical low density, mid density, and high density calibration standards
used for the calibration of these gauges.
12. Density Systems Verification
12.1 For gauges that have undergone at least one previous density systems calibration and have not undergone any repairs or
modifications that can affect the gauge geometry or the accuracy of the existing calibration curve, one may perform a density
systems verification in lieu of a density system calibration. The frequency of density systems calibrations is given inThe
verification of the density system means that it fulfills specified requirements. Those specified requirements are that the
measurement errors of the wet density readings obtained by the calibrated gauge under specified conditions do not 9.11. exceed
a specified density value.
D7759/D7759M − 21
10.2 The density system verification may be done by the gauge manufacturer, the user, or an independent vendor.
12.2 For any specific density system verification process, the uncertainty in density measurements over the range of densities for
which gauges verified in this manner are used shall be known. Uncertainties shall be known for a single maximum uncertainty
value applicable to the entire density range of the gauge, or, at a minimum, one value from each of the following three density
levels:The verification for a density system of the gauge shall be performed at the conclusion of either Procedure A or Procedure
B calibrations.
3 3
10.3.1 At a density level within 5 % of the lower extreme of the density calibration range (typically 1755 kg/m [109.6 lbm/ft ]).
3 3
10.3.2 At a density level within 5 % of the mid value of the density calibration range (typically 2145 kg/m [133.9 lbm/ft ]).
3 3
10.3.3 At a density level within 5 % of the upper extreme of the density calibration range (typically 2612 kg/m [163.1 lbm/ft ]).
12.3 For a density system that has just completed a successful density system verification, the maximum permissible measurement
error for in place density measured by the gauge on a density standard typically does not exceed 32 kg/mThe verification process
for a calibration performed using Procedure A may be accomplished by next performing the calibration procedure defined in
3 3
Procedure B for each density system, then computing the absolute measurement error for each comparison [2 lbm/ft ] of the
density value assigned to the standard. This assigned density of this standard is based upon the density response of a typical gauge
of this type on the standard.measured by the gauge and the associated soil-equivalent density of the density standard upon which
the measurement was made.
NOTE 2—In 9.9 and 10.3, three density levels are specified as points at which the gauge density measurement uncertainty must be knows for the specific
calibration method. Three points are used because, at a minimum, three points define the mathematical form of the calibration curve for the density
measurement system. The values of the three ranges were selected to reflect the range of the typical low density, mid density, and high density calibration
standards used for the calibration of these gauges.
12.3.1 In the instance where the density system verification process follows 12.3, the maximum permissible absolute measurement
error for in place density measured by the gauge on a density standard used in the calibration process typically does not exceed
3 3
16 kg/m [1 lbm/ft ] of the density value assigned to the standard. This assigned density of this standard is based upon the density
response of a typical gauge of this type on the standard.
12.4 In the instance where the density system calibration is performed using Procedure A and the verification process is performed
using other empirical, historical, or statistical evaluations not directly related to the empirical method described in 12.3, the
maximum permissible absolute measurement error for in place density calculated by this method on a density standard typically
3 3
does not exceed 16 kg ⁄m [1 lbm ⁄ft ] of the density value assigned to the standard. This assigned density of this standard is based
upon the density response of a typical gauge of this type on the standard.
12.5 In the instance where the density system calibration was performed using Procedure B and new calibration constants were
not computed prior to this calibration, the maximum permissible absolute measurement error for in place density calculated by this
3 3
method on a density standard typically does not exceed 32 kg ⁄m [2 lbm ⁄ft ] of the density value assigned to the standard. This
assigned density of this standard is based upon the density response of a typical gauge of this type on the standard.
12.6 In instances where there are more than three density calibration standards used in either a Procedure A or Procedure B
calibration, the permissible absolute measurement error could exceed the values described in 12.3 through 12.5 due to regression
errors and/or regression residuals.
12.7 Failure to meet the specified measurement errors requires that the calibration constants be calculated again, so Calibration
Procedure A must be performed.
12.8 The density content system of the gauge shall undergo a calibration and verification at periods not to exceed twelve months.
13. Standards Used for Density Systems Calibration and Verification
13.1 The density value(s) of any manufactured metallic, natural stone, or non-soil standard used in the calibration or verification
D7759/D7759M − 21
of the density system of the gauge shall be determined in such a manner that the estimated standard deviation of the measurement
results used in this determination shall not exceed 0.5%0.5 % of the measured standard density or densities.
13.2 The density value(s) assigned to a standard that is comprised of materials that have the potential to change over time in
density, such as soil, concrete, or solid rock, typically need to be reestablished or verified at periods not exceeding twelve months.
If the standard material is shown to maintain its density within the estimated standard deviation described in 11.113.1 for the
environment in which it is stored and used, then the reestablishment or verification period can be extended accordingly.
13.3 The density response of a nuclear gauge is influenced by both the density of the material and the elemental composition of
the material. The contribution of the elemental composition of the material to the density r
...