How to select sensors reasonably

Modern sensors are very different in principle and structure. How to select a sensor reasonably according to the specific measurement purpose, measurement object and measurement environment is the first problem to be solved when measuring a certain quantity. When the sensor is confirmed, the measuring method and measuring equipment matched with it can also be confirmed. The success or failure of the measurement result depends to a large extent on the different principles and structures of modern sensors. How to select the sensor reasonably according to the specific measurement purpose, the measurement object and the measurement environment is the first step in the measurement of a certain quantity. The problem to be solved. When the sensor is confirmed, the measuring method and measuring equipment matched with it can also be confirmed. The success or failure of the measurement result depends to a large extent on whether the selection of the sensor is reasonable.　　1. Determine the type of sensor according to the measurement object and measurement environment. 　　 To perform a specific measurement, first consider the principle of the sensor, which needs to be determined after analyzing many factors. Because, even if it is measuring the same physical quantity, there are sensors with multiple principles to choose from. Which principle sensor is more suitable, you need to consider the following specific issues according to the characteristics of the measured and the use conditions of the sensor: the size of the range; The measured position requires the volume of the sensor; whether the measurement method is contact or non-contact; the signal extraction method, wired or non-contact measurement; the source of the sensor, whether it is domestic or imported, and whether the price is affordable, or self-developed.　　 After considering the above issues, we can determine which type of sensor to choose, and then consider the specific performance indicators of the sensor.　　2, the choice of sensitivity　　 Generally, within the linear range of the sensor, it is hoped that 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 conducive to signal processing. But it should be noted that the sensitivity of the sensor is high, and external noise that has nothing to do with the measurement is also easy to mix in, and it will also be amplified by the amplification system, which affects the measurement accuracy. Therefore, it is required that the sensor itself should have a higher signal-to-noise ratio, and try to reduce the factory disturbance signal introduced from the outside.　　 The sensitivity of the sensor is directional. When the measured is a single vector, and its directivity requirements are high, the sensor with less sensitivity in other directions should be selected; if the measured is a multi-dimensional vector, the smaller the cross sensitivity of the sensor, the better.　　3, frequency response characteristics 　　The frequency response characteristics of the sensor determine the frequency range to be measured, and the measurement conditions must be kept undistorted within the allowable frequency range. In fact, the response of the sensor always has a fixed delay, and it is hoped that the delay time is as short as possible. The frequency response of the sensor is high, and the measurable signal frequency range is wide. Due to the influence of the structural characteristics, the inertia of the mechanical system is larger, and the frequency of the measurable signal is lower due to the low-frequency sensor.　　In dynamic measurement, the response characteristics should be based on the characteristics of the signal (steady state, transient, random, etc.) to avoid over-fire errors. 　　4. Linear range　　The linear range of the sensor refers to the range in which the output is proportional to the input. In theory, the sensitivity remains constant within this range. The wider the linear range of the sensor, the larger the measuring range, and a certain measurement accuracy can be guaranteed. When selecting a sensor, when the type of sensor is determined, it is first necessary to see 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 the 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 that affect the long-term stability of the sensor are mainly the use environment of the sensor. Therefore, in order for the sensor to have good stability, the sensor must have strong environmental adaptability.　　Before selecting a sensor, investigate its use environment, and select the appropriate sensor according to the specific use environment, or take appropriate measures to reduce the environmental impact.　　The stability of the sensor has a quantitative index. After the expiration date, it should be re-calibrated before use to determine whether the performance of the sensor has changed.　　In some occasions where the sensor can be used for a long time but cannot be easily replaced or calibrated, the stability of the selected sensor is more stringent and must be able to withstand the test for a long time.　　6. u200bu200bAccuracy 　　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 too high. In this way, a cheaper and simpler sensor can be selected among many sensors that meet the same measurement purpose.　　 If the purpose of the measurement is qualitative analysis, select a sensor with high repeatability accuracy. It is not advisable to select a sensor with high absolute value accuracy; if it is for quantitative analysis, it is necessary to obtain an accurate measurement value, and a sensor with an accuracy level that can meet the requirements should be selected.　　For some special occasions, if you can't choose a suitable sensor, you need to design and manufacture the sensor by yourself. The performance of the self-made sensor should meet the requirements of use.