ASTM F2070-2000(2006) Standard Specification for Transducers Pressure and Differential Pressure Electrical and Fiber-Optic《压力和差动压力电及光纤换能器标准规范》.pdf

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1、Designation: F 2070 00 (Reapproved 2006)An American National StandardStandard Specification forTransducers, Pressure and Differential, Pressure, Electricaland Fiber-Optic1This standard is issued under the fixed designation F 2070; the number immediately following the designation indicates the year o

2、foriginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers the requirements for pressurean

3、d differential 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

4、 all 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 applicationsar

5、e included in Supplementary Requirements S1, S2, and S3.2. Referenced Documents2.1 ASTM Standards:2D 3951 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 inDes

6、ign/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 thedefi

7、nitions 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 appli

8、ed to 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 comm

9、on mode 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 co

10、nditionsspecified 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)

11、3.1.9 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 fibe

12、r-optic 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)1This specification is under the jurisdiction of ASTM Committee F25 on Shipsand Mari

13、ne Technology and is the direct responsibility of Subcommittee F25.10 onElectrical.Current edition approved Feb. 1, 2006. Published February 2006. Originallyapproved in 2000. Last previous edition approved in 2000 as F 2070 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orc

14、ontact ASTM Customer Service at serviceastm.org. For Annual 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 Internation

15、al Organization for Standardization (ISO), 1 rue deVaremb, 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.3.1.11 insulation resistancethe resistance measured be-tween insulated portio

16、ns of a transducer and between theinsulated portions of a transducer and ground when a specifieddc voltage is applied under specified conditions.3.1.12 line pressurethe pressure relative to which a dif-ferential pressure transducer measures pressure.(ANSI/ISA S37.1)3.1.13 operating environmental con

17、ditionsenvironmentalconditions 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 materials, that is enclosed

18、 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 convertthe sensed pressu

19、re 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 measur-and that can be applied to a transducer without causing achange in performance

20、 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 pressure transducer.3.1.21 pr

21、ocess 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 reproduceoutput readings when

22、 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 sensing elementthat par

23、t 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 detects fluid pressure b

24、y 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 the coordinates ofthe low

25、er 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 partstransducer components with at le

26、astone 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 transducer type, range, applicat

27、ion, 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 transducer may be hermetica

28、lly 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 the body of the transdu

29、cer. 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 response may be sensed dir

30、ectly 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 differential transformers

31、(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 differential transformer results

32、 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 change in resistance whi

33、chtranslates 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 change in resistancedue

34、 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 bridge becomes elec-trically

35、 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 withF 2070 00 (2006)2changes in pressure. Typically, a diaphragm is positionedbetween t

36、wo stator plates. Pressure-induced diaphragm deflec-tion changes the circuit capacitance, which is detected andtranslated into a change in voltage output.4.2.1.5 Variable Reluctance TransducerVariable reluc-tance pressure transducers sense changes in reluctance withchanges in pressure. Typically, a

37、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 transducersconsist of crysta

38、ls 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-Perot InterferometerFabry

39、-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 causes a measurable chang

40、e 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 properties of thefiber

41、. 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 wavelength of the reflected lig

42、ht,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. Thesecond resonator vibrates a

43、t 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 Membrane/DiaphragmDefle

44、ctionThe 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 membrane is propor-tional t

45、o 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, differential;pressure (gage, absol

46、ute 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 provided as a generalcompar

47、ison 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 low- or high-pressuremea

48、surement, 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 the sensor elementand c

49、ore, 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 response may suffer depen