IEST RP-DTE011 1-2004 Mechanical Shock and Vibration Transducer.pdf

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1、INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Design, Test, and Evaluation Division Recomended Practice 01.1 IEST-RP-DTE01.1 Mechanical Shock and Vibration Transducer Selection INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Arlington Place One 2340 S. Arlington Heights Road, Suite 10 Arling

2、ton Heights, IL 6005-4516 Phone: (847) 981-010 Fax: (847) 981-4130 E-mail: iestiest.org Web: ww.iest.org 2 Copyrighted material INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY IEST-RP-DTE01.1 IEST-RP-DTE01.1 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Copyrighted material 3 This Recomended

3、 Practice is published by the INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY to advance the technical and enginering sciences. Its use is entirely voluntary, and determination of its aplicability and suitability for any particular use is solely the responsibility of the user. This Recomended Pra

4、ctice was prepared by and is under the jurisdiction of Working Group 01 of the IEST De-sign, Test, and Evaluation Division. Copyright 204 by the INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY First printing, September 204 ISBN 978-0-974313-1-5 PROPOSAL FOR IMPROVEMENT: The Working Groups of the

5、INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY are continualy working on improvements to their Recomended Practices and Reference Documents. Sugestions from those who use these documents are welcome. If you have a sugestion regarding this document, please use the online Proposal for Improvement

6、form found on the IEST website at ww.iest.org/proposal/form.html. INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Arlington Place One 2340 S. Arlington Heights Road, Suite 10 Arlington Heights, IL 6005-4516 Phone: (847) 981-010 Fax: (847) 981-4130 E-mail: iestiest.org Web: ww.iest.org 4 Copyright

7、ed material INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY IEST-RP-DTE01.1 IEST-RP-DTE01.1 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Copyrighted material 5 Mechanical Shock and Vibration Transducer Selection IEST-RP-DTE011.1 CONTENTS SECTION 1 SCOPE AND LIMITATION7 2 REFERENCES7 3 TERMS

8、 AND EFINITIONS.7 4 BACKGROUND AND PURPOSE1 5 TRANSDUCER TYPES FOR SHOCK AND VIBRATION1 6 DYNAMIC CHARACTERISTICS24 7 ENVIRONMENTAL CHARACTERISTICS28 8 TRANSDUCER INSTALATION31 9 TRANSDUCER RECALIBRATION.3 10 TRANSDUCER SELECTION BY APLICATION34 TABLE 1 COMPARISON OF PE AND IEPE TRANSDUCERS19 FIGURE

9、 1 PIEZOELECTRIC MATERIALS.12 2 CLASIFICATIONS OF CRYSTAL TYPES13 3 EQUIVALENT CIRCUIT OF A PE SENSOR AND A CHARGE AMPLIFIER.14 4 COMON PIEZOELECTRIC ACELEROMETER DESIGNS15 5 SCHEATICS OF IEPE TRANSDUCER15 6 FREQUENCY RESPONSE DROP.16 7 WHEATSTONE BRIDGE.20 8 MONOLITHIC SILICON SENSING ELEMENT OF A

10、PR ACELEROMETER.20 9 BLOCK DIAGRAM OF A VC ACELEROETER.21 10 EXPLODED VIEW OF A MICROMACHINED VC ACELEROMETER.2 1 BLOCK DIAGRAM OF A PENDULOUS SERVO ACELEROETER WITH ELECTROMAGNETIC SERVO MECHANISM23 12 BLOCK DIAGRAM AND EXPLODED VIEW OF A PENDULOUS SERVO ACELEROMETER WITH ELECTROSTATIC SERVO MECHAN

11、ISM.23 13 PHASE RESPONSE OF A SINGLE DOF SYSTE VS. NORMALIZED FREQUENCY.26 14 TRANSVERSE SENSITIVITY.27 15 ADHESIVE MOUNTING.32 16 MAGNETIC OUNTING.32 17 ANGULAR ACELEROMETER USING A LINEAR PAIR.39 APPENDIX A BIBLIOGRAPHY41 6 Copyrighted material INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY IE

12、ST-RP-DTE01.1 IEST-RP-DTE01.1 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Copyrighted material 7 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Design, Test, and Evaluation Division Recommended Practice 011.1 Mechanical Shock and Vibration Transducer Selection IEST-RP-DTE011.1 1 SCOPE AND

13、 LIMITATION The purpose of this Recomended Practice is to pro-vide guidelines for selecting transducers to measure shock and vibration in laboratory and field testing en-vironments. Some special aplications are not covered because of their unique nature and the rapid advance-ments taking place in th

14、eir disciplines. These include a variety of biodynamic and biomechanical tests. Even in those aplications not specificaly adresed, how-ever, these recomendations may be helpful. There are basicaly two clases of motion transducers: fixed-reference and mas-spring (relative motion). Non-contact transdu

15、cers, such as laser interferometric displacement and laser Dopler velocity transducers, are fixed-reference designs. Although they ofer some unique properties, these instruments are used to meas-ure shock and vibration only in aplications where a fixed reference is available, and where their cost, s

16、ize, and physical space and geometry requirements are aceptable. Similarly, video and photographic dis-placement measurement techniques are sometimes useful for motion analysis of large, complex structures or mechanisms, but they are used mostly for verifica-tion. These fixed-reference techniques, w

17、hich have diferent constraints, are discused elsewhere.1,2,3This Recomended Practice wil concentrate on the more comon mas-spring type transducers, with the sens-ing element(s) represented by the spring. The folowing recomendations aply to dynamic measurements on objects over 10 grams, with fre-quen

18、cies ranging from DC (0 Hz) to over 10 kHz. Only measurements of linear (translational) motion are considered; measurement of angular or rotational motion is adresed as an aplication at the end of the document. Recent developments4,5,6in smart sensor technology have the potential to revolutionize th

19、e measurement industry, and play an important role in transducer selection. However, part of the IEE standard di-rectly related to transducer selection had not ben finalized as of publication of this Recomended Practice. We therefore limit our discusion in this document to the basic concept of mixed

20、-mode, point-to-point smart sensor where it is relevant. A complete lok at multi-drop smart sensor technology wil be included in future revisions. 2 REFERENCES It is recomended that the user reference manufac-turers specification and aplication data in the selec-tion and use of equipment. Please se

21、Apendix A: Bibliography for informative resources. 3 TERMS AND EFINITIONS acelerometer A transducer whose instantaneous output is propor-tional to the instantaneous aceleration input. acoustic sensitivity The rated output produced by a non-acoustic trans-ducer in the presence of a specified acoustic

22、 field. back-to-back comparison method A method of performing a sensitivity/frequency re-sponse calibration of an acelerometer by mounting the unit under test to the “back” of a reference stan-dard and comparing the outputs of the two devices. 8 Copyrighted material INSTITUTE OF ENVIRONMENTAL SCIENC

23、ES AND TECHNOLOGY IEST-RP-DTE01.1 base strain sensitivity The rated output produced by an acelerometer in the presence of a specified amount of strain input induced by the bending motion at the mounting interface. bias voltage The DC voltage that apears at the output of the transducer in quiescent s

24、tate (its level is determined and preset by the manufacturer); generaly interferes with receiving recording devices and normaly de-coupled by a high value capacitor in series. charge amplifier (converter) A preamplifier designed for use with high-impedance piezoelectric transducers, comonly refered

25、to as a “charge amp”; consists of an operational amplifier with a capacitor in its fedback lop; output voltage of the amplifier is proportional to the input charge generated by the transducer and independent of the cable capacitance. charge sensitivity The rated output produced by a high-impedance p

26、ie-zoelectric transducer per unit of aceleration or force input (e.g., pC/g). closed-lop acelerometer An acelerometer in which the output generated by deflection in the mas-spring system is used as fed-back in a circuit that closes the lop by physicaly driv-ing the deflected mas back to its equilibr

27、ium position. NOTE: Some manufacturers claim that closed-lop acelerometer designs ofer beter ampli-tude linearity than open-lop designs. compensation resistor A resistor placed in paralel or in series with any of the legs of a piezoresistive acelerometer to corect for the imbalance in the bridge cir

28、cuit and/or sensitiv-ity erors at temperature. compliance voltage The DC suply voltage available to the integral elec-tronics piezoelectric (IEPE) transducer circuitry; usu-aly lower than the power suply voltage due to the voltage drop in the constant curent device(s). discharge time constant The RC

29、 time constant determined by the design of a transducers circuit topology; time required for the signal level to reduce to 37% of its original value. dynamic range The ratio of the highest level to the lowest level of signal to be measured, expresed in dB. electrical isolation A condition in which t

30、he output and ground leads of the transducer are electricaly isolated from the mounting surface. electromagnetic rebalancing A type of closed-lop acelerometer that uses elec-tromagnetic mechanism to rebalance the deflected mas. electromagnetic sensitivity The rated output produced by an acelerometer

31、 in the presence of a specified electromagnetic field. electrostatic rebalancing A type of closed-lop acelerometer that uses elec-trostatic mechanism to rebalance the deflected mas. feroelectric A subset in the piezoelectric family of materials that typicaly has high dielectric constant. Example: Le

32、ad Zirconate Titanate (PZT) fixed-reference transducer A two-terminal transducer in which one terminal is fixed at a point in space as reference and the other terminal is atached to the object in motion. force transducer A transducer whose output is proportional to the force input. gage factor An in

33、dicator of eficiency for strain gages, which is the ratio of the resistance change to the length change. hermeticaly sealed A sealing method used in transducer design; usualy acompanied by a welded construction and a glas-to-metal seal in the conector. integral electronics piezoelectric (IEPE) A pie

34、zoelectric transducer with a built-in preampli-fier to convert the high-impedance input into a low-impedance voltage output. integral mechanical isolator An acelerometer with a built-in mechanical isolator in one single package; considered superior to an external mechanical isolator because the tran

35、sfer characteristics of the system can be clearly defined. laser Dopler velocity transducer An instrument that uses the Dopler shift of laser light that has ben backscatered from a vibrating object to produce a real-time analog signal propor-tional to instantaneous velocity. laser interferometric di

36、splacement transducer An instrument that uses an interferometric fringe counting technique for vibration-displacement meas-urement in low-frequency ranges. IEST-RP-DTE01.1 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Copyrighted material 9 linear variable diferential transformer (LVDT) A varia

37、ble inductance transducer that provides an AC voltage output proportional to the displacement of a core pasing through its internal windings. linearity (nonlinearity) The constant (or non-constant) behavior of the ratio of the electrical output of a transducer to the me-chanical input; typicaly stat

38、ed as a percentage of ful scale based on a best-fit straight line, or as a percent-age of reading. mas-loading eror An eror in the structural response induced by the aded mas of the acelerometer. Rule-of-thumb: The acelerometer should weigh les than one-tenth of the test object. mas-spring (relative

39、 motion) transducer A transducer that has only one terminal atached to its base and is atached to the object in motion; the mo-tion of the device is infered from the motion of the mas (of the mas-spring system) relative to the base. mean time betwen failure (MTBF) An established method of calculatin

40、g and predicting the service life of an instrument. micro electro-mechanical systems (MEMS) A sensor that uses etching and micromachine fabrica-tion techniques in forming its components; typicaly les than 1 m square. NOTE: MEMS technology can be aplied to piezoelectric, piezoresistive, variable capa

41、ci-tance, or other types of design. micromachining A manufacturing proces that produces the entire sensing mechanism from a single piece of silicon by using anisotropic etching technique. noise monitor A dumy transducer that poseses al of the electrical and physical characteristics of a real transdu

42、cer except for dynamic response, usualy produced by replacing or desensitizing the sensing element(s); useful in as-sesing the quality of the output signal in the presence of environmental noise. noise-treated cable A type of cable designed to minimize triboelectric noise in a high-impedance piezoel

43、ectric transducer system; also known as low-noise cable. open-lop acelerometer An acelerometer in which the output generated by the deflection in the mas-spring system is used directly to indicate aceleration (cf. closed-lop acelerometer). overange capability The ability of a transducer to withstand

44、 excesive me-chanical input beyond its stated ful-scale range with-out sustaining permanent damage. picoCoulomb (pC) A comon unit of charge from a PE transducer; 1012Coulomb. piezoelectric (PE) transducer A transducer that utilizes piezoelectric elements as the spring in its mas-spring system and pr

45、oduces an electric charge proportional to the aplied input. piezoelectric coeficients The measure of the amount of charge produced per unit of input force; unit is in picoCoulomb per Newton. piezoresistive (PR) transducer A transducer that utilizes piezoresistive elements as the spring in its mas-sp

46、ring system, resulting in a change in resistance proportional to the aplied input. pyroelectric efect The phenomenon in which an electric charge is pro-duced when a transducer is subjected to a thermal transient input; relates primarily to piezoelectric transducers. pyroshock The response of a struc

47、ture to a high-frequency, high-magnitude shock wave as a result of an explosive event; also known as pyrotechnic shock. RAD rating An indicator used by the nuclear industry to represent the level of integrated gama radiation. reciprocity method A primary vibration calibration method that uses a shak

48、er designed with two coils, one to provide mo-tion, one to measure the motion; the shaker is a recip-rocal transducer, able to sense or drive, with a sensitivity factor relating the ratio of the drive curent to force, to the ratio of pickup voltage to velocity. resolution The lowest level of signal

49、that can be measured by a transducer, usualy stated in terms of equivalent engi-nering unit; other terms, such as residual noise and threshold, are also used to represent the same parameter. resonance frequency The frequency for which the response of a system un-dergoing forced, steady-state vibration is a maximum. NOTE: The mounted resonance frequency is usu-aly higher than the unmounted resonance (the natural frequency of the device). When a trans-ducer is mounted to a rigid structure, the stifnes of the system increases as a result. 10 Copyrighted material IN