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1、英文文献翻译Basic knowledge of transducersA tran sducer is a device which conv erts the qua ntity being measured into an optical, mecha ni cal, or-more com monly-electrical sig nal. The en ergy-c on versi on process that takes place is referred to as tran sduct ion.Tran sducers are classified accordi ng t
2、o the tran sducti on prin ciple invo Ived and the form of the measured. Thus a resista nee tran sducer for measuri ng displaceme nt is classified as a resista nee displaceme nt tran sducer. Other classificati on examples are pressure bellows, force diaphragm, pressure flapper- no zzle, and so on.1、T
3、ransducer ElementsAlthough there are excepti on ,most tran sducers con sist of a sensing eleme nt and a conv ersi on or con trol eleme nt. For example, diaphragms,bellows,stra in tubes and rin gs, bourd on tubes, and can tilevers are sensing eleme nts which resp ond to cha nges in pressure or force
4、and convert these physical qua ntities into a displaceme nt. This displaceme nt may the n be used to cha nge an electrical parameter such as voltage, resista nee, capacita nee, or in ducta nee. Such comb in atio n of mecha ni cal and electrical eleme nts form electromecha ni cal tran sduci ng device
5、s or tran sducers. Similar comb in ati on can be made for other en ergy in put such as thermal. Photo, magn etic and chemical,givi ng thermoelectric, photoelectric,electromaa netic, and electrochemical tran sducers respectively.2、Transducer SensitivityThe relati on ship betwee n the measured and the
6、 tran sducer output sig nal is usually obta ined by calibrati on tests and is referred to as the tran sducer sen sitivity K1= output-sig nal in creme nt / measured in creme nt .In practice, the tran sducer sen sitivity is usually known, and, by measuri ng the output sig nal, the in put qua ntity is
7、determ ined from in put= output-sig nal in creme nt / K1.3、Characteristics of an Ideal TransducerThe high tran sducer should exhibit the followi ng characteristicsa) high fidelity-the tran sducer output waveform shape be a faithful reproducti on of the measured; there should be mi nimum distortio n.
8、b) There should be minimum in terfere nee with the qua ntity being measured; the prese nee of the tran sducer should not alter the measured in any way.c) Size. The tran sducer must be capable of being placed exactly where it is n eeded.d) There should be a lin ear relati on ship betwee n the measure
9、d and the tran sducer sig nal.e) The tran sducer should have mi nimum sen sitivity to exter nal effects, pressuretran sducers,for example,are ofte n subjected to exter nal effects such vibrati on and temperature.f) The n atural freque ncy of the tran sducer should be well separated from the freque n
10、cy and harm onics of the measura nd.4、Electrical TransducersElectrical tran sducers exhibit many of the ideal characteristics. In additi on they offer high sen sitivity as well as promot ing the possible of remote in dicati on or mesdureme nt.Electrical tran sducers can be divided into two disti net
11、 groups:a) variable-c on trol-parameter types,which in clude:i) resista neeii) capacita neeiii) in ducta neeiv) mutual-in ducta nee typesThese tran sducers all rely on exter nal excitatio n voltage for their operati on.b) self-ge nerati ng types,which in eludei) electromag neticii) thermoelectriciii
12、) photoemissiveiv) piezo-electric typesThese all themselves produce an output voltage in resp onse to the measura nd in put and their effects are reversible. For example, a piezo-electric tran sducer n ormally produces an output voltage in resp onse to the deformati on of a crystalli ne material; ho
13、wever, if an alter nat ing voltage is applied across the material, the tran sducer exhibits the reversible effect by deform ing or vibrati ng at the freque ncy of the alter nati ng voltage.5、Resista nee Tran sducersResista nee tran sducers may be divided in to two groups, as follows:i) Those which e
14、xperie nee a large resista nee cha nge, measured by using pote ntial-divider methods. Pote ntiometers are in this group.ii) Those which experie nee a small resista nee cha nge, measured by bridge-circuit methods. Examples of this group in elude strain gauges and resista nee thermometers.5.1 Pote nti
15、ometersA lin ear wire-wo und pote ntiometer eon sists of a nu mber of turns resista nee wire wound around a non-eon duct ing former, together with a wipi ng eon tact which travels over the barwires. The eon struct ion prin ciples are show n in figure which in dicate that the wiperdisplaceme nt can b
16、e rotary, tran slati on al, or a comb in ati on of both to give a helical-type motio n. The excitati on voltage may be either a.c. or d.c. and the output voltage is proporti onal to the in put moti on, provided the measuri ng device has a resista nee which is much greater tha n the pote ntiometer resista nee.Such pote ntiometers suffer from the lin ked problem of resolutio n and electrical no ise.Resoluti on is
