1、Designation: F2070 00 (Reapproved 2011)An American National StandardStandard Specification forTransducers, Pressure and Differential, Pressure, Electricaland Fiber-Optic1This standard is issued under the fixed designation F2070; the number immediately following the designation indicates the year ofo
2、riginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers the requirements for pressureand d
3、ifferential pressure transducers for general applications.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly. Where information is to be specified, it shall be stated inSI units.1.3 This standard does not purport to address al
4、l of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices, and determine the applica-bility of regulatory limitations prior to use.1.4 Special requirements for naval shipboard applicationsare i
5、ncluded in Supplementary Requirements S1, S2, and S3.2. Referenced Documents2.1 ASTM Standards:2D3951 Practice for Commercial Packaging2.2 ANSI/ISA Standards:ANSI/ISA S37.1 Electrical Transducer Nomenclature andTerminology32.3 ISO Standard:ISO 9001 Quality SystemModel for Quality Assurance inDesign/
6、Development, Production, Installation, and Ser-vicing43. Terminology3.1 Terms marked with (ANSI/ISAS37.1) are taken directlyfrom ANSI/ISA S37.1 (R-1982) and are included for theconvenience of the user.DefinitionsTerminology consistentwith ANSI/ISA S37.1 shall apply, except as modified by thedefiniti
7、ons listed as follows:3.1.1 absolute pressurepressure measured relative to zeropressure (vacuum). (ANSI/ISA S37.1)3.1.2 ambient conditionsconditions such as pressure andtemperature of the medium surrounding the case of thetransducer. (ANSI/ISA S37.1)3.1.3 burst pressurethe maximum pressure applied t
8、o thetransducer sensing element without rupture of the sensingelement or transducer case as specified.3.1.4 calibrationthe test during which known values ofmeasurands are applied to the transducer and correspondingoutput readings are recorded under specified conditions.(ANSI/ISA S37.1)3.1.5 common m
9、ode pressurethe common mode pressureis static line pressure applied simultaneously to both pressuresides of the transducer for the differential pressure transduceronly.3.1.6 differential pressurethe difference in pressure be-tween two points of measurement. (ANSI/ISA S37.1)3.1.7 environmental condit
10、ionsspecified external condi-tions, such as shock, vibration, and temperature, to which atransducer may be exposed during shipping, storage, handling,and operation. (ANSI/ISA S37.1)3.1.8 errorthe algebraic difference between the indicatedvalue and the true value of the measurand.(ANSI/ISA S37.1)3.1.
11、9 fiber-optic pressure transducera device that con-verts fluid pressure, by means of changes in fiber-opticproperties, to an output that is a function of the appliedmeasurand. The fiber-optic pressure transducer normally con-sists of a sensor head, optoelectronics module, and connector-ized fiber-op
12、tic cable.3.1.10 hysteresisthe maximum difference in output, at anymeasurand value within the specified range, when the value isapproached first with increasing and then with decreasingmeasurand. (ANSI/ISA S37.1)3.1.11 insulation resistancethe resistance measured be-tween insulated portions of a tra
13、nsducer and between theinsulated portions of a transducer and ground when a specifieddc voltage is applied under specified conditions.1This specification is under the jurisdiction of ASTM Committee F25 on Shipsand Marine Technology and is the direct responsibility of Subcommittee F25.10 onElectrical
14、.Current edition approved April 1, 2011. Published April 2011. Originallyapproved in 2000. Last previous edition approved in 2006 as F2070 00(2006).DOI: 10.1520/F2070-00R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For A
15、nnual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.4Available from International Organization for Standardization (ISO), 1 rue deVar
16、emb, Case postale 56, CH-1211, Geneva 20, Switzerland.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.12 line pressurethe pressure relative to which a dif-ferential pressure transducer measures pressure.(ANSI/ISA S37.1)3.1.13 ope
17、rating environmental conditionsenvironmentalconditions during exposure to which a transducer must performin some specified manner. (ANSI/ISA S37.1)3.1.14 opticalinvolving the use of light-sensitive devicesto acquire information.3.1.15 optical fibera very thin filament or fiber, made ofdielectric mat
18、erials, that is enclosed by material of lower indexof refraction and transmits light throughout its length byinternal reflections.3.1.16 optoelectronics modulea component of the fiber-optic pressure transducer that contains the optical source anddetector, and signal conditioner devices necessary to
19、convertthe sensed pressure to the specified output signal.3.1.17 outputelectrical or numerical quantity, producedby a transducer or measurement system, that is a function ofthe applied measurand.3.1.18 overpressurethe maximum magnitude of mea-surand that can be applied to a transducer without causin
20、g achange in performance beyond the specified tolerance.3.1.19 pressure cyclingthe specified minimum number ofspecified periodic pressure changes over which a transducerwill operate and meet the specified performance.3.1.20 pressure ratingthe maximum allowable appliedpressure of a differential press
21、ure transducer.3.1.21 process mediumthe measured fluid (measurand)that comes in contact with the sensing element.3.1.22 rangemeasurand values, over which a transduceris intended to measure, specified by their upper and lowerlimits. (ANSI/ISA S37.1)3.1.23 repeatabilityability of a transducer to repro
22、duceoutput readings when the same measurand value is applied toit consecutively, under the same conditions, and in the samedirection. (ANSI/ISA S37.1)3.1.24 responsethe measured output of a transducer to aspecified change in measurand.3.1.25 ripplethe peak-to-peak ac component of the dcoutput.3.1.26
23、 sensing elementthat part of the transducer thatresponds directly to the measurand. (ANSI/ISA S37.1)3.1.27 sensitivity factorthe ratio of the change in trans-ducer output to a change in the value of the measurand.3.1.28 sensor headthe transduction element of the fiber-optic pressure transducer that
24、detects fluid pressure by meansof changes in optical properties.3.1.29 signal conditioneran electronic device that makesthe output signal from a transduction element compatible witha readout system.3.1.30 static error bandstatic error band is the maximumdeviation from a straight line drawn through t
25、he coordinates ofthe lower range limit at specified transducer output, and theupper range limit at specified transducer output expressed inpercent of transducer span.3.1.31 transducerdevice that provides a usable output inresponse to a specified measurand. (ANSI/ISA S37.1)3.1.32 wetted partstransduc
26、er components with at leastone surface in direct contact with the process medium.4. Classification4.1 DesignationMost transducer manufacturers use des-ignations or systematic numbering or identifying codes. Onceunderstood, these designations could aid the purchaser inquickly identifying the transduc
27、er type, range, application, andother parameters.4.2 DesignPressure transducers typically consist of asensing element that is in contact with the process medium anda transduction element that modifies the signal from thesensing element to produce an electrical or optical output.Some parts of the tra
28、nsducer may be hermetically sealed ifthose parts are sensitive to and may be exposed to moisture.Pressure connections must be threaded with appropriate fittingsto connect the transducer to standard pipe fittings or to otherappropriate leak-proof fittings. The output cable must besecurely fastened to
29、 the body of the transducer. A variety ofsensing elements are used in pressure transducers. The mostcommon elements are diaphragms, bellows, capsules, Bourdontubes, and piezoelectric crystals. The function of the sensingelement is to produce a measurable response to appliedpressure or vacuum. The re
30、sponse may be sensed directly onthe element or a separate sensor may be used to detect elementresponse. The following is a brief introduction to the majorpressure sensing technology design categories.4.2.1 Electrical Pressure Transducers:4.2.1.1 Differential Transformer TransducerLinear vari-able di
31、fferential transformers (LVDT) are variable reluctancedevices. Pressure-induced sensor movement, usually transmit-ted through a mechanical linkage, moves a core within adifferential transformer. Sensors are most commonly bellows,capsules, or Bourdon tubes. The movement of the core withinthe differen
32、tial transformer results in a change in reluctancethat translates to a voltage output. An amplifying mechanicallinkage may be used to obtain adequate core movement.4.2.1.2 Potentiometric TransducerPressure-inducedmovement of the sensing element causes movement of apotentiometer wiper resulting in a
33、change in resistance whichtranslates to a voltage output. A bellows or Bourdon tube iscommonly used as the sensing element. An amplifying me-chanical linkage may be used to obtain adequate wipermovement.4.2.1.3 Strain Gage TransducerTypical strain gage pres-sure transducers convert a pressure into a
34、 change in resistancedue to strain which translates to a relative voltage output.Pressure-induced movement in the sensing element deformsstrain elements. The strain elements of a typical strain gagepressure transducer are active arms of a Wheatstone Bridgearrangement. As pressure increases, the brid
35、ge becomes elec-trically unbalanced as a result of the deformation of the strainelements providing a change in voltage output.4.2.1.4 Variable Capacitance TransducerVariable capaci-tance pressure transducers sense changes in capacitance withchanges in pressure. Typically, a diaphragm is positionedbe
36、tween two stator plates. Pressure-induced diaphragm deflec-tion changes the circuit capacitance, which is detected andtranslated into a change in voltage output.F2070 00 (2011)24.2.1.5 Variable Reluctance TransducerVariable reluc-tance pressure transducers sense changes in reluctance withchanges in
37、pressure. Typically, a diaphragm is positionedbetween two ferric core coil sensors that when excited producea magnetic field. Pressure-induced diaphragm deflectionchanges the reluctance, which is detected and translated to achange in voltage output.4.2.1.6 Piezoelectric TransducerPiezoelectric trans
38、ducersconsist of crystals made of quartz, tourmaline, or ceramicmaterial. Pressure-induced changes in crystal electrical prop-erties cause the crystal to produce an electrical output which isdetected and translated to a change in voltage output.4.2.2 Fiber-Optic Pressure Transducers:4.2.2.1 Fabry-Pe
39、rot InterferometerFabry-Perot interfer-ometers (FPI) consist of two mirrors facing each other, thespace between the mirrors being called the cavity length. Lightreflected in the FPI is wavelength modulated in exact accor-dance with the cavity length. Pressure-induced movement ofone of the mirrors ca
40、uses a measurable change in cavity lengthand a phase change in the reflected light signal. This change isoptically detected and processed.4.2.2.2 Bragg Grating InterferometerA Bragg grating iscontained in a section about 1 cm long and acts as a narrowband filter that detects variation in the optical
41、 properties of thefiber. When the fiber is illuminated with an ordinary lightsource such as an LED, only a narrow band of light will bereflected back from the grating section of the fiber. If a pressureis applied to the grating section of the fiber, the grating periodchanges, and hence, the waveleng
42、th of the reflected light,which can be measured.4.2.2.3 Quartz ResonatorsTypically, a pair of quartz reso-nators are inside the pressure transducer. These are excited bythe incoming optical signal. One resonator is load-sensitive andvibrates at a frequency determined by the applied pressure. Theseco
43、nd resonator vibrates at a frequency that varies with theinternal temperature of the transducer. Optical frequency sig-nals from the resonators are transmitted back to the optoelec-tronics interface unit. The interface unit provides an output oftemperature-compensated pressure.4.2.2.4 Micromachined
44、Membrane/DiaphragmDeflectionThe sensing element is made on a silicon substrateusing photolithographic micromachining. The deflection of thismicromachined membrane is detected and measured usinglight. The light is delivered to the sensor head through anoptical fiber. The light returning from the memb
45、rane is propor-tional to the pressure deflection of the membrane and isdelivered back to a detector through an optical fiber. The fiberand the sensor head are packaged within a thin tubing.4.3 TypesThe following are common types of pressureand differential pressure transducers: pressure, differentia
46、l;pressure (gage, absolute and sealed); pressure, vacuum; andpressure, compound.4.4 Process MediumThe following are the most commontypes of process media: freshwater, oil, condensate, steam,nitrogen and other inert gases, seawater, flue gas and ammonia,and oxygen.4.5 ApplicationThe following is prov
47、ided as a generalcomparison of different types of transducers and considerationsfor application.4.5.1 LVDT TransducerThe sensor element may becomecomplicated depending on the amount of motion required forcore displacement. Careful consideration should be exercisedwhen the application includes very l
48、ow- or high-pressuremeasurement, overpressure exposure, or high levels of vibra-tion. Careful consideration should also be exercised whenmeasuring differential pressure of process media having highdielectric constants, especially liquid media. If the processmedia is allowed to enter the gap between
49、the sensor elementand core, accuracy may suffer. Frequency response may sufferdepending on the type of mechanical linkage(s) used in thetransducer.4.5.2 Potentiometric Pressure TransducerPotentiometricpressure transducers are generally less complicated than otherdesigns. Careful consideration should be exercised when theapplication includes very low pressure measurement, overpres-sure exposure, high levels of vibration, stability and repeatabil-ity over extended periods of time, or extremely high resolutionrequirements. Frequency r
