电气工程及其自动化专业英语,主编 杨勇 邓秋玲,Unit 7 Sensoring Technology,7.1 Introduction,7.3 Further Reading,7.2 Sensors,7.1 Introduction,New Words and Expressions,sensor n. 传感器 detector n. 发现者；探测器；检波器；检电器 instrument n. 工具；手段；器械；器具；手段 mercury n. 水银，汞 thermometer n. 温度计；体温计 calibrate v. 校准 elevator n. 电梯；升降机 tactile adj. 触觉的；有触觉的；能触知的,New Words and Expressions,dim adj. 暗淡的；悲观的；怀疑的 vt. 使暗淡；使失去光泽 brighten v. （使）变亮；（使）愉快 sensitivity n. 敏感；灵敏（度）；灵敏性 characteristic adj. 特有的；表示特性的；典型的 n. 特性；特征 microscopic adj. 用显微镜可见的；精微的 infrared adj. 红外线的 n. 红外线,7.1 Introduction,New Words and Expressions,property n. 财产；所有物；所有权；性质；特性 logarithmic adj. 对数的 deviation n. 背离 offset n. 偏移量；抵消；弥补；分支 vt. 弥补；抵消 vi. 偏移；形成分支 bias n. 偏见；偏爱；斜线 vt. （使）存偏见 bode n. 波特图 drift n. 冲洗；漂流物；观望；漂流 v.（使）漂流,7.1 Introduction,New Words and Expressions,degradation n. 降级；降格；退化 lag n. 落后；迟延；防护套 adj. 最后的 vi. 缓缓而行；滞后 vt. 落后于 aliasing n. 数混淆现象 stimuli n. 激励 threshold n. 开始；开端；极限；阈值 fatigue n. 疲乏；疲劳；累活 vt. 使疲劳； 使心智衰弱 vi. 疲劳 faint n. 昏晕；昏倒 adj. 衰弱的；无力的； 暗淡的 vi. 昏倒；变得微弱,7.1 Introduction,A sensor (also called detector) is a converter that measures a physical quantity and converts it into a signal which can be read by an observer or by an (today mostly electronic) instrument. For example, as shown in Fig.7.1, a mercury-in-glass thermometer converts the measured temperature into expansion or contraction of a liquid which can be read on a calibrated glass tube. A thermocouple converts temperature to an output voltage which can be read by a voltmeter. For accuracy, most sensors are calibrated against known standards.,7.1 Introduction text,Sensors are used in everyday objects such as touch-sensitive elevator buttons (tactile sensor) and lamps which dim or brighten by touching the base. There are also innumerable applications for sensors of which most people are never aware. Applications include cars, machines, aerospace, medicine, manufacturing and robotics.,As shown in Fig.7.2，a sensor is a device which receives and responds to a signal. A sensors sensitivity indicates how much the sensors output changes when the measured quantity changes. For instance, if the mercury,7.1 Introduction text,in a thermometer moves 1cm when the temperature changes by 1, the sensitivity is 1cm/ (it is basically the slope Dy/Dx assuming a linear characteristic). Sensors that measure very small changes must have very high sensitivities. Sensors also have an impact on what they measure; for instance, a room temperature thermometer inserted into a hot cup of liquid cools the liquid while the liquid heats the thermometer. Sensors need to be designed to have a small effect on what is measured; making the sensor smaller often improves this and may introduce other advantages. Technological,7.1 Introduction text,progress allows more and more sensors to be manufactured on a microscopic scale as microsensors using MEMS technology. In most cases, a microsensor reaches a significantly higher speed and sensitivity compared with macroscopic approaches.,A good sensor obeys the following rules: Is it sensitive to the measured property only? Is it insensitive to any other property likely to be encountered in its application? Does it not influence the measured property?,7.1 Introduction text,Ideal sensors are designed to be linear or linear to some simple mathematical function of the measurement, typically logarithmic. The output signal of such a sensor is linearly propertional to the value or simple function of the measured property. The sensitivity is then defined as the ratio between output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the sensitivity is a constant with the unit V/K; this sensor is linear because the ratio is constant at all points of measurement.,7.1 Introduction text,If the sensor is not ideal, several types of deviations can be observed: The sensitivity may in practice differ from the value specified. This is called a sensitivity error, but the sensor is still linear. Since the range of the output signal is always limited, the output signal will eventually reach a minimum or maximum when the measured property exceeds the limits. The full scale range defines the maximum and minimum values of the measured property.,7.1 Introduction text, If the output signal is not zero when the measured property is zero, the sensor has an offset or bias. This is defined as the output of the sensor at zero input. If the sensitivity is not constant over the range of the sensor, this is called non-linearity. Usually this is defined by the amount the output differs from ideal behavior over the full range of the sensor, often noted as a percentage of the full range. If the deviation is caused by a rapid change of the measured property over time, there is a dynamic error. Often, this behavior is descr