ASTM E74-00a

Standard Practice of Calibration of Force-Measuring Instruments for Verifying the Force Indication of Testing Machines

SCOPE
1.1 The purpose of this practice is to specify procedures for the calibration of force-measuring instruments. Procedures are included for the following types of instruments:
1.1.1 Elastic force-measuring instruments, and
1.1.2 Force-multiplying systems, such as balances and small platform scales.
Note 1—Verification by deadweight loading is also an acceptable method of verifying the force indication of a testing machine. Tolerances for weights for this purpose are given in Practices E 4; methods for calibration of the weights are given in NIST Technical Note 577, Methods of Calibrating Weights for Piston Gages.
1.2 The values stated in SI units are to be regarded as the standard. Other metric and inch-pound values are regarded as equivalent when required.
1.3 This practice is intended for the calibration of static force measuring instruments. It is not applicable for dynamic or high speed force calibrations, nor can the results of calibrations performed in accordance with this practice be assumed valid for dynamic or high speed force measurements.
1.4 This standard 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 standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 04-Apr-2002
• ICS: 17.100 - Measurement of force, weight and pressure
• Technical Committee: E28 - Mechanical Testing
• Drafting Committee: E28.01 - Calibration of Mechanical Testing Machines and Apparatus

Relations

• Replaced By: ASTM E74-01 - Standard Practice of Calibration of Force-Measuring Instruments for Verifying the Force Indication of Testing Machines
• Effective Date: 05-Apr-2002
• Referred By: ASTM E139-11(2018) - Standard Test Methods for Conducting Creep, Creep-Rupture, and Stress-Rupture Tests of Metallic Materials
• Effective Date: 05-Apr-2002
• Referred By: ASTM C1196-20 - Standard Test Method for In Situ Compressive Stress Within Solid Unit Masonry Estimated Using Flatjack Measurements
• Effective Date: 05-Apr-2002
• Referred By: ASTM D76/D76M-21 - Standard Specification for Tensile Testing Machines for Textiles
• Effective Date: 05-Apr-2002
• Referred By: ASTM E92-23 - Standard Test Methods for Vickers Hardness and Knoop Hardness of Metallic Materials
• Effective Date: 05-Apr-2002
• Referred By: ASTM F3109-23 - Standard Practice for Verification of Multi-Axis Force Measuring Platforms
• Effective Date: 05-Apr-2002
• Referred By: ASTM F377-03(2022) - Standard Practice for Calibration of Braking/Tractive Measuring Devices for Testing Tires
• Effective Date: 05-Apr-2002
• Referred By: ASTM E10-23 - Standard Test Method for Brinell Hardness of Metallic Materials
• Effective Date: 05-Apr-2002
• Referred By: ASTM C900-19 - Standard Test Method for Pullout Strength of Hardened Concrete
• Effective Date: 05-Apr-2002
• Referred By: ASTM E21-20 - Standard Test Methods for Elevated Temperature Tension Tests of Metallic Materials
• Effective Date: 05-Apr-2002
• Referred By: ASTM E18-22 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 05-Apr-2002
• Referred By: ASTM C39/C39M-21 - Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens
• Effective Date: 05-Apr-2002
• Referred By: ASTM E3205-20 - Standard Test Method for Small Punch Testing of Metallic Materials
• Effective Date: 05-Apr-2002
• Referred By: ASTM E3098-17 - Standard Test Method for Mechanical Uniaxial Pre-strain and Thermal Free Recovery of Shape Memory Alloys
• Effective Date: 05-Apr-2002
• Referred By: ASTM F1062-97(2018) - Standard Test Method for Verification of Ski Binding Test Devices
• Effective Date: 05-Apr-2002

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: E 74 – 00a An American National Standard
Standard Practice of
Calibration of Force-Measuring Instruments for Verifying the
Force Indication of Testing Machines
This standard is issued under the fixed designation E 74; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope B46.1 Surface Texture
1.1 The purpose of this practice is to specify procedures for
ELASTIC FORCE-MEASURING INSTRUMENTS
the calibration of force-measuring instruments. Procedures are
included for the following types of instruments:
3. Terminology
1.1.1 Elastic force-measuring instruments, and
3.1 Definitions:
1.1.2 Force-multiplying systems, such as balances and small
3.1.1 elastic force-measuring device—a device or system
platform scales.
consisting of an elastic member combined with a device for
NOTE 1—Verification by deadweight loading is also an acceptable indicating the magnitude (or a quantity proportional to the
method of verifying the force indication of a testing machine. Tolerances
magnitude) of deformation of the member under an applied
for weights for this purpose are given in Practices E 4; methods for
force.
calibration of the weights are given in NIST Technical Note 577, Methods
3.1.2 primary force standard—a deadweight force applied
of Calibrating Weights for Piston Gages.
directly without intervening mechanisms such as levers, hy-
1.2 The values stated in SI units are to be regarded as the
draulic multipliers, or the like, whose mass has been deter-
standard. Other metric and inch-pound values are regarded as
mined by comparison with reference standards traceable to
equivalent when required.
national standards of mass.
1.3 This practice is intended for the calibration of static
3.1.3 secondary force standard—an instrument or mecha-
force measuring instruments. It is not applicable for dynamic
nism, the calibration of which has been established by com-
or high speed force calibrations, nor can the results of
parison with primary force standards.
calibrations performed in accordance with this practice be
3.2 Definitions of Terms Specific to This Standard:
assumed valid for dynamic or high speed force measurements.
3.2.1 calibration equation—a mathematical relationship be-
1.4 This standard does not purport to address all of the
tween deflection and force established from the calibration data
safety concerns, if any, associated with its use. It is the
for use with the instrument in service, sometimes called the
responsibility of the user of this standard to establish appro-
calibration curve.
priate safety and health practices and determine the applica-
3.2.2 continuous-reading device—a class of instruments
bility of regulatory limitations prior to use.
whose characteristics permit interpolation of forces between
calibrated forces.
2. Referenced Documents
3.2.2.1 Discussion—Such instruments usually have force-
2.1 ASTM Standards:
to-deflection relationships that can be fitted to polynominal
E 4 Practices for Force Verification of Testing Machines
equations. Departures from the fitted curve are reflected in the
E 29 Practice for Using Significant Digits in Test Data to
uncertainty (8.4).
Determine Conformance with Specifications
3.2.3 deflection—the difference between the reading of an
2.2 American National Standard:
instrument under applied force and the reading with no applied
force.
3.2.4 loading range—a range of forces within which the
uncertainty is less than the limits of error specified for the
This practice is under the jurisdiction of ASTM Committee E28 on Mechanical
instrument application.
Testingand is the direct responsibility of Subcommittee E28.01 on Calibration of
3.2.5 reading—a numerical value indicated on the scale,
Mechanical Testing Machines and Apparatus.
Current edition approved Oct. 10, 2000. Published January 2001. Originally
dial, or digital display of a force-measuring instrument under a
published as E 74 – 47 T. Last previous edition E 74 – 00.
given force.
Available from National Institute for Standards and Technology, Gaithersburg,
MD 20899.
Annual Book of ASTM Standards, Vol 03.01.
4 5
Annual Book of ASTM Standards, Vol 14.02. Available from American National Standards Institute, 11 W. 42nd St., 13th
Floor, New York, NY 10036.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E74
3.2.6 resolution—the smallest reading or indication appro-
9.80665 = the factor converting SI units of force into the
priate to the scale, dial, or display of the force measuring
customary units of force. For SI units, this factor
instrument.
is not used.
3.2.7 specific force device—an alternative class of instru-
6.1.2 The masses of the weights shall be determined within
ments not amenable to the use of a calibration equation.
0.005 % of their values by comparison with reference stan-
3.2.7.1 Discussion—Such instruments, usually those in
dards traceable to the national standards of mass. The local
which the reading is taken from a dial indicator, are used only
value of the acceleration due to gravity, calculated within
at the calibrated forces. These instruments are also called
0.0001 m/s (10 milligals), may be obtained from the National
limited-load devices.
Geodotic Information Center, National Oceanic and Atmo-
3.2.8 uncertainty—a statistical estimate of the limits of
spheric Administration.
error in forces computed from the calibration equation of a
NOTE 2—If M, the mass of the weight, is in pounds, the force will be
force–measuring instrument when the instrument is calibrated
in pound-force units (lbf). If M is in kilograms, the force will be in
in accordance with this practice.
kilogram-force units (kgf). These customary force units are related to the
newton (N), the SI unit of force, by the following relationships:
4. Significance and Use
1 lbf 5 4.448 22 N (2)
4.1 Testing machines that apply and indicate force are in
1 kgf 5 9.806 65 N ~exact!
general use in many industries. Practices E 4 has been written
The pound-force (lbf) is defined as that force which, applied to a 1-lb
to provide a practice for the force verification of these
mass, would produce an acceleration of 9.80665 m/s/s.
machines. A necessary element in Practices E 4 is the use of The kilogram-force (kgf) is defined as that force which, applied to a
1-kg mass, would produce an acceleration of 9.80665 m/s/s.
devices whose force characteristics are known to be traceable
to national standards. Practice E 74 describes how these
6.2 Secondary Standards—Secondary force standards may
devices are to be calibrated. The procedures are useful to users
be either elastic force-measuring instruments used in conjunc-
of testing machines, manufacturers and providers of force
tion with a machine or mechanism for applying force, or some
measuring instruments, calibration laboratories that provide the
form of mechanical or hydraulic mechanism to multiply a
calibration of the instruments and the documents of traceabil-
relatively small deadweight force. Examples of the latter form
ity, and service organizations that use the devices to verify
include single- and multiple-lever systems or systems in which
testing machines.
a force acting on a small piston transmits hydraulic pressure to
a larger piston.
5. Reference Standards
6.2.1 Elastic force-measuring instruments used as second-
ary standards shall be calibrated by primary standards and used
5.1 Force-measuring instruments used for the verification of
only over the Class AA loading range (see 8.5.2.1). Secondary
the force indication systems of testing machines may be
standards having capacities exceeding 1 000 000 lbf (4.4 MN)
calibrated by either primary or secondary standards.
are not required to be calibrated by primary standards. Several
5.2 Force-measuring instruments used as secondary stan-
secondary standards of equal compliance may be combined
dards for the calibration of other force-measuring instruments
and loaded in parallel to meet special needs for higher
shall be calibrated by primary standards. An exception to this
capacities. The uncertainty (see 8.4) of such a combination
rule is made for instruments having capacities exceeding the
shall be calculated by adding in quadrature using the following
range of available primary standards. Currently the maximum
equation:
primary force-standard facility in the United States is
1 000 000-lbf (4.4-MN) deadweight calibration machine at the
2 2 2 2
U 5 = U 1 U 1 U 1 . U (3)
c o 1 2 n
National Institute of Standards and Technology.
where:
6. Requirements for Force Standards
U = uncertainty of the combination, and
c
U = uncertainty of the individual instruments.
o, 1, 2.n
6.1 Primary Standards—Weights used as primary force
standards shall be made of rolled, forged, or cast metal.
6.2.2 The multiplying ratio of a force multiplying system
Adjustment cavities shall be closed by threaded plugs or
used as a secondary standard shall be measured at not less than
suitable seals. External surfaces of weights shall have a finish
three points over its range with an accuracy of 0.05 % of ratio
of 125 or less as specified in ANSI B46.1.
or better. Some systems may show a systematic change in ratio
6.1.1 The force exerted by a weight in air is calculated as
with increasing force. In such cases the ratio at intermediate
follows:
points may be obtained by linear interpolation between mea-
Mg d
sured values. Deadweights used with multiplying-type second-
Force 5 1 2 (1)
S D
9.80665 D
ary standards shall meet the requirements of 6.1 and 6.1.2. The
force exerted on the system shall be calculated from the
where:
relationships given in 6.1.1. The force multiplying system shall
M = mass of the weight,
g = local acceleration due to gravity, m/s , be checked annually by elastic force measuring instruments
d = air density (approximately 0.0012 Mg/m ),
D = density of the weight in the same units as d
Available from the National Oceanic and Atmospheric Administration, Rock-
(Note 4), and
ville, MD.
E74
influence factors outlined above which exhibits continued change of
used within their class AA loading ranges to ascertain whether
degree of best fit with several successive calibrations may not have
the forces applied by the system are within acceptable ranges
sufficient performance stability to allow application of the curve fitting
as defined by this standard. Changes exceeding 0.05 % of
procedure of Annex A1.
applied force shall be cause for reverification of the force
multiplying system. 7.2 Selection of Calibration Forces— A careful selection of
the different forces to be applied in a calibration is essential to
7. Calibration
provide an adequate and unbiased sample of the full range of
7.1 Basic Principles—The relationship between the applied the deviations discussed in 7.1 and 7.1.1. For this reason, the
force and the deflection of an elastic force-measuring instru- selection of the calibration forces is made by the standardizing
ment is, in general, not linear. As force is applied, the shape of laboratory. An exception to this, and to the recommendations of
the elastic element changes, progressively altering its resis- 7.2.1 and 7.2.4, is made for specific force devices, where the
tance to deformation. The result is that the slope of the selection of the forces is dictated by the needs of the user.
force-deflection curve changes gradually and uniformly over 7.2.1 Distribution of Calibration Forces— Distribute the
the entire range of the instrument. This characteristic full-scale calibration forces over the full range of the instrument,
nonlinearity is a stable property of the instrument that is providing, if possible, at least one calibration force for every
changed only by a severe overload or other similar cause. 10 % interval throughout the range. It is not necessary, how-
7.1.1 Localized Nonlinearities—Superposed on this curve ever that these forces be equally spaced. Calibration forces at
are localized nonlinearities introduced by the imperfections in less than one tenth of capacity are permissible and tend to give
the force indicating system of the instrument. Examples of added assurance to the fitting of the calibration equation. If the
imperfections include: non-uniform scale or dial graduations, lower limit of the loading range of the device (see 8.5.1) is
irregular wear between the contacting surfaces of the vibrating anticipated to be less than one tenth of the maximum force
reed and button in a proving ring, and voltage and sensing applied during calibration, then forces should be applied at or
instabilities in a load cell system. Some of these imperfections below this lower limit. In no case should the smallest force
are less stable than the full-scale nonlinearity and may change applied be below the theoretical lower limit of the instrument
significantly from one calibration to another. as defined by the values:
7.1.2 Curve Fitting—In the treatment of the calibration
400 3 resolution for Class A loading range (4)
data, a second degree polynomial fitted to the observed data
2000 3 resolution for Class AA loading range
using the method of least squares has been found to predict
An example of a situation to be avoided is the calibration at
within the limit of the uncertainty (8.4) deflection values for
ten equally spaced force increments of a proving ring having a
applied force throughout the loading range of the elastic force
capacity deflection of 2000 divisions, where the program will
measuring instrument. Such an equation compensates effec-
fail to sample the wear pattern at the contacting surfaces of the
tively for the full-scale nonlinearity, allowing the localized
micrometer screw tip and vibrating reed because the orienta-
nonlinearities to appear as deviations. A statistical estimate,
tion of the two surfaces will be nearly the same at all ten forces
called the uncertainty, is made of the width of the band of these
as at zero force. Likewise, in a load cell calibration, forces
deviations about the basic curve. The uncertainty is, therefore,
selected to give readings near the step-switch points will fail to
an estimate of the limits of error contributed by the instrument
sample the slidewire irregularities or mismatching of the
when forces measured in service are calculated by means of the
slidewire span to the step-switch increments.
calibration equation. Actual errors in service are likely to be
7.2.2 The re
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