How to choose correctly
In general, in the linear range of sensors, 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. However, it should be noted that the sensitivity of the sensor is high, and external noise that is not related to the measurement is easily mixed, and it is also amplified by the magnification system, affecting the measurement accuracy. Therefore, the sensor itself is required to have a higher signal-to-noise ratio and reduce the number of noise signals introduced from the outside world.
Modern sensors vary greatly in principle and structure. How to select sensors reasonably according to the specific measurement purpose, measurement object and measurement environment is the first problem to be solved when making a certain amount of measurement. When the sensor is determined, the corresponding measurement method and measurement equipment can also be determined. The success or failure of the measurement results depends to a large extent on whether the selection of sensors is reasonable.
Select Steps and Methods
1. Determine the type of sensor based on the measurement object and the measurement environment
To perform a specific measurement, it is necessary to first consider what kind of sensors are used. This requires analysis of many factors before it can be determined. Because, even if the same physical quantity is measured, there are multiple principle sensors available. The sensor of which principle is more suitable needs 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; Requirements of the measured position for sensor volume; The measurement method is contact or non-contact; Signal extraction method, wire or non-contact measurement; The source of sensors, domestic or imported, the price can bear, or self-developed.
2. Selection of Sensitivity
Often, in 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. However, it should be noted that the sensitivity of the sensor is high, and external noise that is not related to the measurement is easily mixed, and it is also amplified by the magnification system, affecting the measurement accuracy. Therefore, the sensor itself is required to have a higher signal-to-noise ratio and reduce the number of noise signals introduced from the outside world.
Sensor sensitivity is directional. When the measurement is a one-way quantity and the directionality requirement is higher, the sensor with less sensitivity in other directions should be selected. If the measurement is a multidimensional vector, the lower the cross-sensitivity of the sensor is required, the better.
The frequency response characteristics of the sensor determine the frequency range to be measured. The measurement conditions must be maintained within the allowed frequency range. In fact, the sensor’s response always has a definite delay. It is hoped that the shorter the delay time, the better.
The frequency response of the sensor is high, and the measurable signal frequency range is wide. Due to the influence of the structure characteristics, the inertia of the mechanical system is relatively large, because the frequency of the sensor’s measurable signal with low frequency is low.
In dynamic measurement, response characteristics(steady state, transient, random, etc.) should be used to avoid excessive error.
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 range, and can ensure a certain measurement accuracy. When selecting the sensor, when the type of sensor is determined, it first depends on whether the 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, the sensor with less nonlinear error can be approximated as linear within a certain range, which will bring great convenience to the measurement.
After the sensor is used for a period of time, its ability to maintain its performance unchanged is called stability. In addition to the structure of the sensor itself, the main factor affecting the long-term stability of the sensor is 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, the environment in which it is used should be investigated and suitable sensors should be selected according to the specific environment of use, or appropriate measures should be taken to reduce the impact of the environment.
The stability of the sensor has quantitative indicators. After the expiration of the service life, it should be re-calibrated before use to determine whether the performance of the sensor has changed.
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 precision of the sensor, the more expensive it is. Therefore, the accuracy of the sensor can only meet the accuracy requirements of the entire measurement system, and it is not necessary to select too high. In this way, a relatively cheap and simple sensor can be selected among the many sensors that meet the same measurement purpose.
If the purpose of the measurement is qualitative analysis, the sensor with high repetition accuracy can be used, and it is not appropriate to select the absolute value with high accuracy; If it is for quantitative analysis, it is necessary to obtain accurate measurement values, and it is necessary to select sensors whose accuracy level can meet the requirements.