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1. Determine the type of sensor according to the measurement object and measurement environment
To carry out a specific measurement work, we must first consider which principle sensor is used, which can only be determined after analyzing various factors. Because, even for the measurement of the same physical quantity, there are sensors with a variety of principles to choose from. Which sensor is more suitable, you need to consider the following specific issues according to the characteristics of the measured and the conditions of use of the sensor: the size of the range; The requirements of the measured position on the sensor volume; whether the measurement method is contact or non-contact; the signal extraction method, wired or non-contact measurement. After considering the above problems, you can determine which type of sensor to choose, and then consider the sensor specific performance indicators.
2. The choice of sensitivity
Generally, within the linear range of the sensor, the higher the sensitivity of the sensor, the better. Because only when the sensitivity is high, the value of the output signal corresponding to the measured change is relatively large, which is beneficial to signal processing. However, it should be noted that the sensitivity of the sensor is high, and the external noise unrelated to the measurement is also easily mixed, and it will also be amplified by the amplification system, affecting the measurement accuracy.
3. Frequency response characteristics
The frequency response characteristics of the sensor determine the frequency range to be measured, and the measurement conditions must be maintained without distortion within the allowable frequency range. In fact, the response of the sensor always has a certain delay, and it is hoped that the shorter the delay time, the better. The frequency response of the sensor is high, the frequency range of the measurable signal is wide, and due to the influence of the structural characteristics, the inertia of the mechanical system is large, and the frequency of the measurable signal of the sensor with low frequency is low. In dynamic measurement, the response characteristics should be based on the characteristics of the signal (steady-state, transient, random, etc.) to avoid excessive errors.
4. Linear range
The linear range of the sensor is the range in which the output is proportional to the input. Theoretically, within this range, the sensitivity remains constant. The wider the linear range of the sensor, the larger its range, and can guarantee a certain measurement accuracy. When selecting a sensor, when the type of the sensor is determined, it first depends on whether its range meets the requirements. But in fact, no sensor can guarantee absolute linearity, and its linearity is also relative. When the required measurement accuracy is relatively low, within a certain range, the sensor with less nonlinear error can be approximately regarded as linear, which will bring great convenience to the measurement.
5. Stability
The ability of a sensor to keep its performance unchanged after a period of use is called stability. In addition to the structure of the sensor itself, the factors affecting the long-term stability of the sensor are mainly the use environment of the sensor. Therefore, to make the sensor have good stability, the sensor must have strong environmental adaptability. Before selecting a sensor, the use environment should be investigated, and the appropriate sensor should be selected according to the specific use environment, or appropriate measures should be taken to reduce the impact of the environment. The stability of the sensor has quantitative indicators. After the period of use, it should be re-calibrated before use to determine whether the performance of the sensor has changed. In some occasions where the sensor is required to be used for a long time but cannot be easily replaced or calibrated, the selected sensor has stricter stability requirements and must be able to withstand the test of a long time.
6. Precision
Accuracy is an important performance index of the sensor, and it is an important link related to the measurement accuracy of the entire measurement system. The higher the accuracy of the sensor, the more expensive it is. Therefore, the accuracy of the sensor only needs to meet the accuracy requirements of the entire measurement system, and it is not necessary to select it too high. This makes it possible to choose a cheaper and simpler sensor among many sensors for the same measurement purpose. If the purpose of measurement is qualitative analysis, a sensor with high repeatability can be selected, and it is not appropriate to use a sensor with high absolute value accuracy; if it is for quantitative analysis, it is necessary to obtain accurate measurement values, and it is necessary to select a sensor with an accuracy level that meets the requirements. For some special occasions, if a suitable sensor cannot be selected, it is necessary to design and manufacture the sensor by itself. The performance of the self-made sensor should meet the requirements for use.
To carry out a specific measurement work, we must first consider which principle sensor is used, which can only be determined after analyzing various factors. Because, even for the measurement of the same physical quantity, there are sensors with a variety of principles to choose from. Which sensor is more suitable, you need to consider the following specific issues according to the characteristics of the measured and the conditions of use of the sensor: the size of the range; The requirements of the measured position on the sensor volume; whether the measurement method is contact or non-contact; the signal extraction method, wired or non-contact measurement. After considering the above problems, you can determine which type of sensor to choose, and then consider the sensor specific performance indicators.
2. The choice of sensitivity
Generally, within the linear range of the sensor, the higher the sensitivity of the sensor, the better. Because only when the sensitivity is high, the value of the output signal corresponding to the measured change is relatively large, which is beneficial to signal processing. However, it should be noted that the sensitivity of the sensor is high, and the external noise unrelated to the measurement is also easily mixed, and it will also be amplified by the amplification system, affecting the measurement accuracy.
3. Frequency response characteristics
The frequency response characteristics of the sensor determine the frequency range to be measured, and the measurement conditions must be maintained without distortion within the allowable frequency range. In fact, the response of the sensor always has a certain delay, and it is hoped that the shorter the delay time, the better. The frequency response of the sensor is high, the frequency range of the measurable signal is wide, and due to the influence of the structural characteristics, the inertia of the mechanical system is large, and the frequency of the measurable signal of the sensor with low frequency is low. In dynamic measurement, the response characteristics should be based on the characteristics of the signal (steady-state, transient, random, etc.) to avoid excessive errors.
4. Linear range
The linear range of the sensor is the range in which the output is proportional to the input. Theoretically, within this range, the sensitivity remains constant. The wider the linear range of the sensor, the larger its range, and can guarantee a certain measurement accuracy. When selecting a sensor, when the type of the sensor is determined, it first depends on whether its range meets the requirements. But in fact, no sensor can guarantee absolute linearity, and its linearity is also relative. When the required measurement accuracy is relatively low, within a certain range, the sensor with less nonlinear error can be approximately regarded as linear, which will bring great convenience to the measurement.
5. Stability
The ability of a sensor to keep its performance unchanged after a period of use is called stability. In addition to the structure of the sensor itself, the factors affecting the long-term stability of the sensor are mainly the use environment of the sensor. Therefore, to make the sensor have good stability, the sensor must have strong environmental adaptability. Before selecting a sensor, the use environment should be investigated, and the appropriate sensor should be selected according to the specific use environment, or appropriate measures should be taken to reduce the impact of the environment. The stability of the sensor has quantitative indicators. After the period of use, it should be re-calibrated before use to determine whether the performance of the sensor has changed. In some occasions where the sensor is required to be used for a long time but cannot be easily replaced or calibrated, the selected sensor has stricter stability requirements and must be able to withstand the test of a long time.
6. Precision
Accuracy is an important performance index of the sensor, and it is an important link related to the measurement accuracy of the entire measurement system. The higher the accuracy of the sensor, the more expensive it is. Therefore, the accuracy of the sensor only needs to meet the accuracy requirements of the entire measurement system, and it is not necessary to select it too high. This makes it possible to choose a cheaper and simpler sensor among many sensors for the same measurement purpose. If the purpose of measurement is qualitative analysis, a sensor with high repeatability can be selected, and it is not appropriate to use a sensor with high absolute value accuracy; if it is for quantitative analysis, it is necessary to obtain accurate measurement values, and it is necessary to select a sensor with an accuracy level that meets the requirements. For some special occasions, if a suitable sensor cannot be selected, it is necessary to design and manufacture the sensor by itself. The performance of the self-made sensor should meet the requirements for use.
