1. What parts do sensors usually consist of?
Sensors generally consist of three parts: sensitive components, conversion components, and signal conditioning conversion circuits. Sometimes an additional auxiliary power supply is required. Provides conversion energy.
1. Sensitive element: refers to the part of the sensor that can directly feel or respond to the measurement.
2. Conversion element: refers to the part of the sensor that can convert the measured value sensed or responded by the sensitive element into an electrical signal suitable for transmission or measurement.
3. Signal conditioning and conversion circuit: Since the sensor output signal is generally very weak, the sensor output signal generally needs signal conditioning and conversion, amplification, calculation and modulation before it can be displayed and controlled.
4. Auxiliary power supply: Conversion components and conversion circuits generally require auxiliary power supply.
2. What are the characteristics of the sensor?
1. Static characteristics
refers to the characteristics of the sensor itself. The main indicators studied are: linearity, accuracy, repeatability, temperature drift, etc. In layman’s terms: the size of the nonlinear error, the size of the linear error, the quality of multiple applications, the size of the error due to temperature changes, etc.
2. Dynamic characteristics
Refers to the characteristics of the output of the sensor when its input changes in the application. It is represented by its response to certain standard input signals, that is, the transfer function in self-control theory. In actual work, it facilitates collection and control in engineering projects.
3. Stability
Stability indicates the sensor’s ability to maintain its performance parameters over a long period of time. The ideal situation is that the characteristic parameters of the sensor do not change with time at any time. But in reality, the characteristics of most sensors change over time. This is because the characteristics of sensitive devices or components that make up the sensor will change over time, thus affecting the stability of the sensor.
4. Linearity
Usually, the actual static characteristic output of the sensor is a curve rather than a straight line. In actual work, in order to make the instrument have a uniform scale reading, a fitting straight line is often used to approximately represent the actual characteristic curve. Linearity (nonlinear error) is a performance index of this approximation. There are many ways to select the fitting straight line. likeThe theoretical straight line connecting the zero input and full-scale output points is used as the fitting straight line; or the theoretical straight line with the smallest sum of square deviations from each point on the characteristic curve is used as the fitting straight line. This fitting straight line is called least squares fitting. straight line.
5. Repeatability
Repeatability refers to the degree of inconsistency in the characteristic curves obtained by the sensor when the input value changes continuously multiple times across the entire range in the same direction. . The closer each characteristic curve is, the better the repeatability and the smaller the random error.
6. Sensitivity
Sensitivity refers to the ratio of the output change Δy of the sensor to the input change Δx under steady-state operating conditions. It is the slope of the output-input characteristic curve. If there is a linear relationship between the sensor’s output and input, the sensitivity S is a constant. Otherwise, it will change with the input amount. The dimension of sensitivity is the ratio of the dimensions of the output and input quantities. For example, for a displacement sensor, when the displacement changes by 1mm, the output voltage changes by 200mV, then its sensitivity should be expressed as 200mV/mm. When the output and input dimensions of the sensor are the same, the sensitivity can be understood as the amplification factor.
7. Resolution
Resolution refers to the ability of the sensor to detect the smallest change in the measured value. That is, if the input quantity changes slowly from some non-zero value. When the input change value does not exceed a certain value, the output of the sensor will not change, that is, the sensor cannot distinguish the change in the input quantity. Only when the change in input exceeds the resolution will the output change. Usually, the resolution of the sensor at each point within the full-scale range is not the same. Therefore, the maximum change value in the input quantity that can cause a step change in the output value in the full-scale range is often used as an indicator to measure the resolution. If the above indicators are expressed as a percentage of full scale, it is called resolution.
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