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To carry out a specific measurement work, we must first consider the principle of sensors, which need to be analyzed after many factors can be determined. Because even the sensors that measure the same physical quantity and have many principles are available, which principle is more suitable, it is necessary to consider the following specific problems based on the characteristics measured and the use conditions of the sensor, the size of the range, the volume of the measured position to the sensor, and the method of measurement. Contact or non contact type; signal elicitation method, cable or non-contact measurement; source of the sensor, domestic or import, price can bear, or self development.
After considering the above problems, we can determine which type of sensors to choose and then consider the specific performance indicators of the sensors.
Usually, in the linear range of the sensor, the higher the sensitivity of the sensor is, the better. Because only when the sensitivity is high, the value of the output signal corresponding to the measured change is larger, which is conducive to signal processing. However, it should be noted that the sensitivity of the sensor is high, and the external noise which is irrelevant to the measurement is also easy to mix in, and it will also be magnified by the amplification system, which will affect the measurement accuracy. Therefore, the sensor itself should have a higher signal-to-noise ratio and minimize interference signals from the outside world.
The sensitivity of the sensor is directional. When the measurement is unidirectional and its directivity is higher, the sensor with small sensitivity in other directions should be selected; if the multidimensional vector is measured, the smaller the cross sensitivity of the sensor, the better.
The frequency response characteristic of the sensor determines the frequency range to be measured and must remain undistorted in the allowable frequency range. In fact, there is always a definite delay in the response of sensors, and the shorter the delay, the better.
The higher the frequency response of the sensor, the wider the frequency range of the measurable signal.
In dynamic measurement, the characteristics of the signal (steady state, transient, random) should be based on the response characteristics, so as to avoid excessive errors.
The linear range of sensors means the range of output and input is directly proportional to the input. In theory, sensitivity is maintained within this range. The wider the linear range of the sensor is, the larger the range is, and the accuracy of measurement can be guaranteed. When selecting sensors, when the type of sensor is determined, we first need to see whether the range meets the requirements.
But in fact, no sensor can guarantee absolute linearity, and its linearity is relative. When the required measurement precision is low, in a certain range, the sensor with smaller nonlinear error can be approximated as linear, which will bring great convenience to the measurement.
The ability of sensors to remain unchanged for a period of time is called stability. The factors that affect the long-term stability of sensors are mainly the use environment of sensors besides the structure of sensors themselves. Therefore, in order to make the sensor have good stability, the sensor must have a strong adaptability to the environment.
Prior to the selection of sensors, the environment should be investigated, and the appropriate sensors are selected according to the specific environment, or appropriate measures are taken to reduce the impact of the environment.
The stability of the sensor has a quantitative index. After exceeding the service life, calibration should be carried out before the use of the sensor to determine whether the performance of the sensor changes.
In some situations where sensors can be used for a long time and can not be easily replaced or calibrated, the stability of the selected sensors is more stringent, and it is necessary to withstand a long test.
Accuracy is an important performance index of sensors. It is an important link related to the measurement accuracy of the whole measuring system. The higher the precision of the sensor, the more expensive it is, so the precision of the sensor can be satisfied as long as it meets the precision requirements of the whole measurement system, and it is not required to be too high. In this way, we can choose more inexpensive and simple sensors for Atlas air compressor parts to meet the same measurement purpose.
If the purpose of the measurement is qualitative analysis, it is not suitable to choose the high precision of the absolute value of the sensor with high repetition precision. If it is for quantitative analysis, the precise measurement value must be obtained, and the precision grade can be selected to meet the requirements of the sensor.
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