Displacement is a quantity related to the movement of the object in the course of motion, and the measuring methods of displacement involve a wide range. Like to keep track of how things are moving, displacement sensors are the fastest way to transmit the data you want. The application of displacement sensor in industry, water conservancy and measurement of liquid level, How to choose a right position sensor?
1. Determine the type of sensor according to the measuring object and the measuring environment
In order to make a concrete measurement, we should first consider the principle of the sensor, we need to consider the following specific problems according to the characteristics of the measured and the conditions of the sensor: The size of the measuring range; The requirements of the measured position on the volume of the sensor; whether the measurement method is contact or non-contact; the method of signal extraction, wired or non-contact measurement; and the selection of the type of sensor, then consider the specific performance indicators of the sensor.
2. Sensitivity selection
In general, in the linear range of the sensor, the higher the sensor’s sensitivity, the better. Because only when the sensitivity is high, and measured change corresponding to the output signal value is relatively large, conducive to signal processing. However, it should be noted that the sensitivity of the sensor is high, and the external noise is easy to be mixed with the measurement, will be amplified by the amplification system, affect the measurement accuracy. Therefore, the sensor itself should be required to have a high signal-to-noise ratio, as much as possible to reduce the disturbance from the outside signal. The sensitivity of the sensor is directional. When the measured vector is unidirectional and requires high directivity, the sensor with low sensitivity in other directions should be selected. If the measured vector is multi-dimensional, the cross sensitivity of the sensor should be as low as possible.
3. Linear range
The linear range of displacement sensor refers to the range in direct proportion to the output and input. In theory, the sensitivity remains constant in this range. The wider the linear range of the sensor is, the larger the measuring range is, and the measurement accuracy is guaranteed to a certain extent. In the selection of sensors, when the type of sensors to determine the first to see whether its range to meet the requirements. But in fact, any sensor can not guarantee the absolute linearity, its linearity is also relative. When the required measurement accuracy is low, the sensor with small nonlinear error can be regarded as linear in a certain range, which will bring great convenience to the measurement.
4. Frequency response characteristics
The Frequency Response Characteristic of the displacement sensor determines the frequency range to be measured, and the measurement condition must be kept in the allowable frequency range without distortion. The frequency response of the sensor is high, the measurable Signal Frequency Range is wide, but because of the influence of the structure characteristic, the inertia of the mechanical system is bigger, because the frequency of the measurable signal of the low frequency sensor is lower. In the dynamic measurement, the characteristics of the signal (steady, transient, random, etc.) response characteristics, so as to avoid excessive error.
Precision is an important performance index of the sensor, and it is an important link related to the measurement accuracy of the whole measurement system. The higher the accuracy of the sensor, the more expensive it is. Therefore, the accuracy of the sensor as long as it meets the accuracy requirements of the whole measurement system can, do not have to choose too high. This allows the selection of cheaper and simpler sensors among many that meet the same measurement purpose.
If the purpose of the measurement is qualitative analysis, the sensor with high repeatability should be selected, and the absolute value with high accuracy should not be selected; if the purpose of the measurement is Quantitative analysis, the precise measurement value must be obtained, it is necessary to select the level of precision to meet the requirements of the sensor.
The ability of a sensor to maintain its performance unchanged after a period of use is called stability. The factors that affect the long-term stability of the sensor, besides the structure of the sensor itself, are mainly the use environment of the sensor. Therefore, to make the sensor have good stability, the sensor must have a strong ability to adapt to the environment. Prior to the selection of sensors, the environment in which they are used should be investigated and the appropriate sensors chosen according to the specific environment in which they are used, or appropriate measures should be taken to reduce the environmental impact. The stability of the sensor has a quantitative index, and should be re-calibrated before use to determine whether the performance of the sensor has changed. In some cases where the sensor can be used for a long time but can not be easily replaced or calibrated, the stability of the selected sensor is required to be more stringent and can stand the test of a long time.