毕业设计外文翻译---传感器的基础知识
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1、 1 1 Basic knowledge of transducers A transducer is a device which converts the quantity being measured into an optical, mechanical, or-more commonly-electrical signal. The energy-conversion process that takes place is referred to as transduction. Transducers are classified according to the transduc
2、tion principle involved and the form of the measured. Thus a resistance transducer for measuring displacement is classified as a resistance displacement transducer. Other classification examples are pressure bellows, force diaphragm, pressure flapper-nozzle, and so on. 1、 Transducer Elements Althoug
3、h there are exception ,most transducers consist of a sensing element and a conversion or control element. For example, diaphragms,bellows,strain tubes and rings, bourdon tubes, and cantilevers are sensing elements which respond to changes in pressure or force and convert these physical quantities in
4、to a displacement. This displacement may then be used to change an electrical parameter such as voltage, resistance, capacitance, or inductance. Such combination of mechanical and electrical elements form electromechanical transducing devices or transducers. Similar combination can be made for other
5、 energy input such as thermal. Photo, magnetic and chemical,giving thermoelectric, photoelectric,electromaanetic, and electrochemical transducers respectively. 2、 Transducer Sensitivity The relationship between the measured and the transducer output signal is usually obtained by calibration tests an
6、d is referred to as the transducer sensitivity K1= output-signal increment / measured increment . In practice, the transducer sensitivity is usually known, and, by measuring the output signal, the input quantity is determined from input= output-signal increment / K1. 3、 Characteristics of an Ideal T
7、ransducer The high transducer should exhibit the following characteristics a) high fidelity-the transducer output waveform shape be a faithful reproduction of the measured; there should be minimum distortion. b) There should be minimum interference with the quantity being measured; the presence of t
8、he transducer should not alter the measured in any way. c) Size. The transducer must be capable of being placed exactly where it is needed. d) There should be a linear relationship between the measured and the transducer signal. e) The transducer should have minimum sensitivity to external effects,
9、pressure 2 2 transducers,for example,are often subjected to external effects such vibration and temperature. f) The natural frequency of the transducer should be well separated from the frequency and harmonics of the measurand. 4、 Electrical Transducers Electrical transducers exhibit many of the ide
10、al characteristics. In addition they offer high sensitivity as well as promoting the possible of remote indication or mesdurement. Electrical transducers can be divided into two distinct groups: a) variable-control-parameter types,which include: i) resistance ii) capacitance iii) inductance iv) mutu
11、al-inductance types These transducers all rely on external excitation voltage for their operation. b) self-generating types,which include i) electromagnetic ii) thermoelectric iii) photoemissive iv) piezo-electric types These all themselves produce an output voltage in response to the measurand inpu
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