Professional Knowledge

Selection principle of sensor

To carry out a specific measurement, the first consideration is what kind of sensor is used. Even if the same physical quantity is measured, there are several kinds of sensors available.
The following questions are considered according to the characteristics of the measured and the conditions for the use of the sensor:
The magnitude of the range;
The requirement of the measured position on the sensor volume;
The measurement method is contact type or non-contact type;
The method of signal extraction, wired or non-contact measurement;
The source of sensors, domestic or imported, affordable or self-developed.
After that, we can decide which kind of sensor to choose and then consider the specific performance index of the sensor.
Sensitivity selection
Generally, within the linear range of the sensor, it is desirable that the sensor be as sensitive as possible. 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. However, it should be noted that the sensitivity of the sensor is high, and the external noise which is irrelevant to the measurement is easy to mix in, which will also be amplified by the amplification system, affecting the measurement accuracy. Therefore, the sensor itself should have a high signal-to-noise ratio to minimize the introduction of interference signals from the outside.
The sensitivity of the sensor is directional. When the sensor is a single vector and has high directional requirements, the sensor with low sensitivity in other directions should be selected. If the measured vector is a multidimensional vector, the smaller the cross sensitivity of the sensor is required.
Frequency response characteristic
The frequency response characteristics of the sensor determine the frequency range to be measured and must remain undistorted within the allowable frequency range. The response of the actual sensor is always a definite delay. The shorter the delay, the better.
The higher the frequency response of the sensor, the wider the signal frequency range can be measured.
In dynamic measurement, response characteristics (steady state, transient, random, etc.) should be adopted to avoid excessive error.
Linear range
The linear range of a sensor is 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 its range, and can guarantee a certain measurement accuracy. When selecting a sensor, the type of sensor should be determined first to see whether its range meets the requirements.
But in fact, no sensor is guaranteed to be absolutely linear, and its linearity is relative. When the measurement precision is relatively low, the sensor with small nonlinear error can be approximately regarded as linear within a certain range, which will bring great convenience to the measurement.
The stability of
The ability of a sensor to maintain its performance unchanged over time is called stability. The environment of the sensor is the factor that affects the long-term stability of the sensor, except for the structure of the sensor itself. The sensor must have strong adaptability to the environment to make the sensor have good stability.
Before selecting the sensor, it shall investigate its use environment, take appropriate measures to reduce the impact of the environment, and select the appropriate sensor according to the use environment.
Precision is an important performance index of sensor, which is an important link of the whole measurement system. The higher the precision of the sensor, the more expensive the price. Therefore, the precision of the sensor can be satisfied as long as the precision requirements of the whole measurement system are met. This allows for the selection of cheaper and simpler sensors, the atlas compressor accessories, among the many sensors available for the same purpose.
If the purpose of measurement is qualitative analysis, the sensor with high repetition precision can be selected. For the purpose of quantitative analysis, accurate measurement values must be obtained, and sensors with the required precision grade should be selected.
For some special use occasions, the suitable sensor cannot be selected, the sensor should be designed and manufactured, and the performance of the self-made sensor should meet the use requirements.