外文翻譯--傳感器的基礎知識-其他專業(yè)-資料下載頁
2025-01-19 09:55本頁面
【導讀】傳感器是一種把被測量轉換為光的、機械的或者更平常的電信號的裝置。過程稱之為換能。按照轉換原理和測量形式對傳感器進行分類。用來測量位移的電阻式傳感器被歸為電。阻式位移傳感器。分類如壓力波紋管、壓力膜和壓力閥等。除特例外，大多數的傳感器都由敏感元件、轉換元件或控制元件組成。然后位移可以改變電參數，如電壓、電阻、電容或者感應系數。子式元件合并形成機電式傳感設備或傳感器。這樣的組合可用來輸入能量信號。的，磁的和化學的相互結合產生的熱電式、光電式、電磁式和電化學式傳感器。通過校正測量系統(tǒng)獲得的被測物理量和傳感器輸出信號的關系叫做傳感器靈敏度K1，出信號，輸入量由下式決定，輸入量=輸出信號增量/K1?？蓽y量最小的干擾，任何時候傳感器的出現不能改變被測量。它們不僅實現遠程測量和顯示，還能提供高靈敏度。xt為最大可能位移，Rt為電位器的電阻。電感可以通過改變電感電路的阻抗來調節(jié)。
【正文】 a linear relationship of resistance against temperature. Thermistors are normally made in the form of semiconductor discs enclosed in glass vitreous enamel. Since they can be made as small as 1mm,quite rapid response times are possible. Photoconductive Cells The photoconductive cell , uses a lightsensitive semiconductor material. The resistance between the metal electrodes decrease as the intensity of the light striking the semiconductor increases. Common semiconductor materials used for photoconductive cells are cadmium sulphide, lead sulphide, and copperdoped germanium. The useful range of frequencies is determined by material used. Cadmium sulphide is mainly suitable for visible light, whereas lead sulphide has its peak response in the infrared region and is, therefore , most suitable for flamefailure detection and temperature measurement. Photoemissive Cells When light strikes the cathode of the photoemissive cell are given sufficient energy to arrive the cathode. The positive anode attracts these electrons, producing a current which flows through resistor R and resulting in an output voltage V. Photoelectrically generated voltage V= Where Ip=photoelectric current(A),and photoelectric current Ip= Where Kt=sensitivity (A/im),and B=illumination input (lumen) Although the output voltage does give a good indication of the magnitude of illumination, the cells are more often used for counting or control purpose, where the light striking the cathode can be interrupted. Capacitive Transducers The capacitance can thus made to vary by changing either the relative permittivity, the effective area, or the distance separating the plates. The characteristic curves indicate that variations of area and relative permittivity give a linear relationship only over a small range of spacings. Thus the sensitivity is high for small values of d. Unlike the potentionmeter, the variabledistance capacitive transducer has an infinite resolution making it most suitable for measuring small increments of displacement or quantities which may be changed to produce a displacement. 第 11 頁 共 11 頁 Inductive Transducers The inductance can thus be made to vary by changing the reluctance of the inductive circuit. Measuring techniques used with capacitive and inductive transducers: （ 1） . excited bridges using differential capacitors inductors. （ 2） . potentiometer circuits for dynamic measurements. （ 3） . circuits to give a voltage proportional to velocity for a capacitor. （ 4） Frequencymodulation methods, where the change of C or L varies the frequency of an oscillation circuit. Important features of capacitive and inductive transducers are as follows: （ 1） resolution infinite （ 2） accuracy+ % of full scale is quoted （ 3） displacement ranges 25*106 m to 103m （ 4） rise time less than 50us possible Typical measurands are displacement, pressure, vibration, sound, and liquid level. Linear Variabledifferential Ttransformer Piezoelectric Transducers Electromagic Transducers 1 Thermoelectric Transducers 1 Photoelectric Cells 1 Mechanical Transducers and Sensing Elements
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