ASTM F2070-00(2006)
(Specification)Standard Specification for Transducers, Pressure and Differential, Pressure, Electrical and Fiber-Optic
Standard Specification for Transducers, Pressure and Differential, Pressure, Electrical and Fiber-Optic
ABSTRACT
This specification covers the requirements for pressure and differential pressure transducers for general applications. Pressure transducers typically consist of a sensing element that is in contact with the process medium and a transduction element that modifies the signal from the sensing element to produce an electrical or optical output. Some parts of the transducer may be hermetically sealed if those parts are sensitive to and may be exposed to moisture. Pressure connections must be threaded with appropriate fittings to connect the transducer to standard pipe fittings or to other appropriate leak-proof fittings. The output cable must be securely fastened to the body of the transducer. Most common sensing elements are diaphragms, bellows, capsules, Bourdon tubes, and piezoelectric crystals. The function of the sensing element is to produce a measurable response to applied pressure or vacuum. The response may be sensed directly on the element or a separate sensor may be used to detect element response. The following are the different types of electrical pressure transducers: differential transformed transducer, potentiometric transducer, strain gage transducer, variable reluctance transducer, and piezoelectric transducer. Different kinds of fiber-optic pressure transducers shall be discussed: Fabry-Perot interferometer, Bragg grating interferometer, quartz resonator, and micromachined membrane/diaphragm deflection. The following physical properties of transducers shall be determined: enclosure, transducer mounting, external configuration, standard electrical connection, pressure connections, damping, size, and weight. Different tests shall be conducted in order to determine the service life and overall performance of the transducers.
SCOPE
1.1 This specification covers the requirements for pressure and differential pressure transducers for general applications.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. Where information is to be specified, it shall be stated in SI units.
1.3 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.
1.3 Special requirements for naval shipboard applications are included in Supplementary Requirements S1, S2, and S3.
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Standards Content (Sample)
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An American National Standard
Designation: F2070 – 00 (Reapproved 2006)
Standard Specification for
Transducers, Pressure and Differential, Pressure, Electrical
and Fiber-Optic
This standard is issued under the fixed designation F2070; 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 convenience of the user.Definitions—Terminology consistent
with ANSI/ISA S37.1 shall apply, except as modified by the
1.1 This specification covers the requirements for pressure
definitions listed as follows:
and differential pressure transducers for general applications.
3.1.1 absolute pressure—pressure measured relative to zero
1.2 The values stated in SI units are to be regarded as the
pressure (vacuum). (ANSI/ISA S37.1)
standard. The values given in parentheses are for information
3.1.2 ambient conditions—conditions such as pressure and
only. Where information is to be specified, it shall be stated in
temperature of the medium surrounding the case of the
SI units.
transducer. (ANSI/ISA S37.1)
1.3 This standard does not purport to address all of the
3.1.3 burst pressure—the maximum pressure applied to the
safety concerns, if any, associated with its use. It is the
transducer sensing element without rupture of the sensing
responsibility of the user of this standard to establish appro-
element or transducer case as specified.
priate safety and health practices, and determine the applica-
3.1.4 calibration—the test during which known values of
bility of regulatory limitations prior to use.
measurands are applied to the transducer and corresponding
1.4 Special requirements for naval shipboard applications
output readings are recorded under specified conditions.
are included in Supplementary Requirements S1, S2, and S3.
(ANSI/ISA S37.1)
2. Referenced Documents 3.1.5 common mode pressure—the common mode pressure
is static line pressure applied simultaneously to both pressure
2.1 ASTM Standards:
sides of the transducer for the differential pressure transducer
D3951 Practice for Commercial Packaging
only.
2.2 ANSI/ISA Standards:
3.1.6 differential pressure—the difference in pressure be-
ANSI/ISA S37.1 Electrical Transducer Nomenclature and
tween two points of measurement. (ANSI/ISA S37.1)
Terminology
3.1.7 environmental conditions—specified external condi-
2.3 ISO Standard:
tions, such as shock, vibration, and temperature, to which a
ISO 9001 Quality System—Model for QualityAssurance in
transducer may be exposed during shipping, storage, handling,
Design/Development, Production, Installation, and Ser-
and operation. (ANSI/ISA S37.1)
vicing
3.1.8 error—the algebraic difference between the indicated
3. Terminology
value and the true value of the measurand.
(ANSI/ISA S37.1)
3.1 Termsmarkedwith(ANSI/ISAS37.1)aretakendirectly
3.1.9 fiber-optic pressure transducer—a device that con-
from ANSI/ISA S37.1 (R-1982) and are included for the
verts fluid pressure, by means of changes in fiber-optic
properties, to an output that is a function of the applied
This specification is under the jurisdiction of ASTM Committee F25 on Ships
measurand. The fiber-optic pressure transducer normally con-
and Marine Technology and is the direct responsibility of Subcommittee F25.10 on
sists of a sensor head, optoelectronics module, and connector-
Electrical.
Current edition approved Feb. 1, 2006. Published February 2006. Originally ized fiber-optic cable.
approved in 2000. Last previous edition approved in 2000 as F2070 – 00. DOI:
3.1.10 hysteresis—themaximumdifferenceinoutput,atany
10.1520/F2070-00R06.
measurand value within the specified range, when the value is
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
approached first with increasing and then with decreasing
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
measurand. (ANSI/ISA S37.1)
the ASTM website.
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036.
Available from International Organization for Standardization (ISO), 1 rue de
Varembé, Case postale 56, CH-1211, Geneva 20, Switzerland.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F2070 – 00 (2006)
3.1.11 insulation resistance—the resistance measured be- upper range limit at specified transducer output expressed in
tween insulated portions of a transducer and between the percent of transducer span.
insulated portions of a transducer and ground when a specified 3.1.31 transducer—device that provides a usable output in
dc voltage is applied under specified conditions. response to a specified measurand. (ANSI/ISA S37.1)
3.1.32 wetted parts—transducer components with at least
3.1.12 line pressure—the pressure relative to which a dif-
one surface in direct contact with the process medium.
ferential pressure transducer measures pressure.
(ANSI/ISA S37.1)
4. Classification
3.1.13 operating environmental conditions—environmental
4.1 Designation—Most transducer manufacturers use des-
conditionsduringexposuretowhichatransducermustperform
ignations or systematic numbering or identifying codes. Once
in some specified manner. (ANSI/ISA S37.1)
understood, these designations could aid the purchaser in
3.1.14 optical—involving the use of light-sensitive devices
quickly identifying the transducer type, range, application, and
to acquire information.
other parameters.
3.1.15 optical fiber—a very thin filament or fiber, made of
4.2 Design—Pressure transducers typically consist of a
dielectric materials, that is enclosed by material of lower index
sensing element that is in contact with the process medium and
of refraction and transmits light throughout its length by
a transduction element that modifies the signal from the
internal reflections.
sensing element to produce an electrical or optical output.
3.1.16 optoelectronics module—a component of the fiber-
Some parts of the transducer may be hermetically sealed if
optic pressure transducer that contains the optical source and
those parts are sensitive to and may be exposed to moisture.
detector, and signal conditioner devices necessary to convert
Pressureconnectionsmustbethreadedwithappropriatefittings
the sensed pressure to the specified output signal.
to connect the transducer to standard pipe fittings or to other
3.1.17 output—electrical or numerical quantity, produced
appropriate leak-proof fittings. The output cable must be
by a transducer or measurement system, that is a function of
securely fastened to the body of the transducer. A variety of
the applied measurand.
sensing elements are used in pressure transducers. The most
3.1.18 overpressure—the maximum magnitude of measur-
common elements are diaphragms, bellows, capsules, Bourdon
and that can be applied to a transducer without causing a
tubes, and piezoelectric crystals. The function of the sensing
change in performance beyond the specified tolerance.
element is to produce a measurable response to applied
3.1.19 pressure cycling—the specified minimum number of
pressure or vacuum. The response may be sensed directly on
specified periodic pressure changes over which a transducer
the element or a separate sensor may be used to detect element
will operate and meet the specified performance.
response. The following is a brief introduction to the major
3.1.20 pressure rating—the maximum allowable applied pressure sensing technology design categories.
pressure of a differential pressure transducer. 4.2.1 Electrical Pressure Transducers:
4.2.1.1 Differential Transformer Transducer—Linear vari-
3.1.21 process medium—the measured fluid (measurand)
able differential transformers (LVDT) are variable reluctance
that comes in contact with the sensing element.
devices. Pressure-induced sensor movement, usually transmit-
3.1.22 range—measurand values, over which a transducer
ted through a mechanical linkage, moves a core within a
is intended to measure, specified by their upper and lower
differential transformer. Sensors are most commonly bellows,
limits. (ANSI/ISA S37.1)
capsules, or Bourdon tubes. The movement of the core within
3.1.23 repeatability—ability of a transducer to reproduce
the differential transformer results in a change in reluctance
output readings when the same measurand value is applied to
that translates to a voltage output. An amplifying mechanical
it consecutively, under the same conditions, and in the same
linkage may be used to obtain adequate core movement.
direction. (ANSI/ISA S37.1)
4.2.1.2 Potentiometric Transducer—Pressure-induced
3.1.24 response—the measured output of a transducer to a
movement of the sensing element causes movement of a
specified change in measurand.
potentiometer wiper resulting in a change in resistance which
3.1.25 ripple—the peak-to-peak ac component of the dc
translates to a voltage output. A bellows or Bourdon tube is
output.
commonly used as the sensing element. An amplifying me-
3.1.26 sensing element—that part of the transducer that
chanical linkage may be used to obtain adequate wiper
responds directly to the measurand. (ANSI/ISA S37.1)
movement.
3.1.27 sensitivity factor—the ratio of the change in trans-
4.2.1.3 Strain Gage Transducer—Typical strain gage pres-
ducer output to a change in the value of the measurand.
sure transducers convert a pressure into a change in resistance
3.1.28 sensor head—the transduction element of the fiber-
due to strain which translates to a relative voltage output.
optic pressure transducer that detects fluid pressure by means
Pressure-induced movement in the sensing element deforms
of changes in optical properties.
strain elements. The strain elements of a typical strain gage
3.1.29 signal conditioner—an electronic device that makes
pressure transducer are active arms of a Wheatstone Bridge
the output signal from a transduction element compatible with
arrangement. As pressure increases, the bridge becomes elec-
a readout system.
trically unbalanced as a result of the deformation of the strain
3.1.30 static error band—static error band is the maximum elements providing a change in voltage output.
deviation from a straight line drawn through the coordinates of 4.2.1.4 Variable Capacitance Transducer—Variable capaci-
the lower range limit at specified transducer output, and the tance pressure transducers sense changes in capacitance with
F2070 – 00 (2006)
changes in pressure. Typically, a diaphragm is positioned 4.4 Process Medium—The following are the most common
between two stator plates. Pressure-induced diaphragm deflec- types of process media: freshwater, oil, condensate, steam,
tion changes the circuit capacitance, which is detected and nitrogen and other inert gases, seawater, flue gas and ammonia,
translated into a change in voltage output. and oxygen.
4.2.1.5 Variable Reluctance Transducer—Variable reluc-
4.5 Application—The following is provided as a general
tance pressure transducers sense changes in reluctance with
comparisonofdifferenttypesoftransducersandconsiderations
changes in pressure. Typically, a diaphragm is positioned
for application.
between two ferric core coil sensors that when excited produce
4.5.1 LVDT Transducer—The sensor element may become
a magnetic field. Pressure-induced diaphragm deflection
complicated depending on the amount of motion required for
changes the reluctance, which is detected and translated to a
core displacement. Careful consideration should be exercised
change in voltage output.
when the application includes very low- or high-pressure
4.2.1.6 Piezoelectric Transducer—Piezoelectric transducers
measurement, overpressure exposure, or high levels of vibra-
consist of crystals made of quartz, tourmaline, or ceramic
tion. Careful consideration should also be exercised when
material. Pressure-induced changes in crystal electrical prop-
measuring differential pressure of process media having high
erties cause the crystal to produce an electrical output which is
dielectric constants, especially liquid media. If the process
detected and translated to a change in voltage output.
media is allowed to enter the gap between the sensor element
4.2.2 Fiber-Optic Pressure Transducers:
and core, accuracy may suffer. Frequency response may suffer
4.2.2.1 Fabry-Perot Interferometer—Fabry-Perot interfer-
depending on the type of mechanical linkage(s) used in the
ometers (FPI) consist of two mirrors facing each other, the
transducer.
space between the mirrors being called the cavity length. Light
4.5.2 Potentiometric Pressure Transducer—Potentiometric
reflected in the FPI is wavelength modulated in exact accor-
pressure transducers are generally less complicated than other
dance with the cavity length. Pressure-induced movement of
designs. Careful consideration should be exercised when the
one of the mirrors causes a measurable change in cavity length
application includes very low pressure measurement, overpres-
and a phase change in the reflected light signal. This change is
sure exposure, high levels of vibration, stability and repeatabil-
optically detected and processed.
ity over extended periods of time, or extremely high resolution
4.2.2.2 Bragg Grating Interferometer—A Bragg grating is
requirements.Frequencyresponsemaysufferdependingonthe
contained in a section about 1 cm long and acts as a narrow
type of mechanical linkage(s) used. Technological advances
band filter that detects variation in the optical properties of the
have yielded more reliable designs that are commonly used.
fiber. When the fiber is illuminated with an ordinary light
4.5.3 Strain Gage Transducers—Low-level output strain
source such as an LED, only a narrow band of light will be
gage transducers are among the most common pressure trans-
reflectedbackfromthegratingsectionofthefiber.Ifapressure
ducers. They are available in very compact packages which
is applied to the grating section of the fiber, the grating period
lend well in applications in which size is critical. Strain gage
changes, and hence, the wavelength of the reflected light,
transducers that demonstrate high degrees of accuracy and
which can be measured.
excellent frequency response characteristics are readily avail-
4.2.2.3 Quartz Resonators—Typically, a pair of quartz reso-
able. Careful consideration should be exercised when the
nators are inside the pressure transducer. These are excited by
application includes very low-pressure measurement, very low
theincomingopticalsignal.O
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