Once the sensor is determined, the corresponding measurement method and equipment can also be determined. The success or failure of the measurement results largely depends on whether the selection of sensors is reasonable.

1. Selection of sensitivity

Generally, within the linear range of a sensor, it is desirable for the sensor's sensitivity to be as high as possible. Only when the sensitivity is high will the value of the output signal corresponding to the change in the measured quantity be relatively large, which is conducive to signal processing. However, it should be noted that due to the high sensitivity of the sensor, external noise unrelated to the measured quantity is also prone to be mixed in and amplified by the amplification system, affecting the measurement accuracy. Therefore, the sensor itself should have a high signal-to-noise ratio and minimize the interference signals introduced from the outside.

The sensitivity of a sensor is directional. When the measured quantity is a unidirectional vector and its directionality is highly demanded, a sensor with low sensitivity in other directions should be selected. If the measured quantity is a multi-dimensional vector, the cross-sensitivity of the sensor should be as small as possible.

2. Frequency response characteristics

The frequency response characteristics of the sensor determine the frequency range of the measured quantity. Undistorted measurement conditions must be maintained within the allowable frequency range. In fact, the response of the sensor always has a certain delay, and it is hoped that the delay time is as short as possible.

The higher the frequency response of a sensor, the wider the measurable signal frequency range. However, due to the influence of structural characteristics, the inertia of mechanical systems is relatively large, so sensors with low frequencies can measure signals with lower frequencies.

In dynamic measurement, the response characteristics should be based on the features of the signal (steady-state, transient, random, etc.) to avoid excessive errors.

3. Determine the type of sensor based on the measured object and the measurement environment

To carry out a specific measurement task, the first step is to consider which principle of sensor should be adopted. This can only be determined after analyzing multiple factors.

Because, even when measuring the same physical quantity, there are multiple types of sensors based on different principles to choose from. To determine which type of sensor is more suitable, the following specific issues need to be considered based on the characteristics of the measured quantity and the usage conditions of the sensor

① The magnitude of the measurement range;

② Requirements for the sensor volume at the measured position;

③ Is the measurement method contact type or non-contact type?

④ Signal extraction method: Wired or non-contact measurement;

⑤ The source of the sensor, whether it is domestic or imported, whether the price is affordable, or whether it is self-developed. After considering the above issues, the type of sensor to be selected can be determined, and then the specific performance indicators of the sensor can be considered.

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4. Linear range

The linear range of a sensor refers to the range where the output is proportional to the input. Theoretically speaking, within this range, the sensitivity remains constant. The wider the linear range of a sensor is, the greater its measurement range will be, and it can ensure a certain measurement accuracy. When choosing a sensor, after the type of sensor is determined, the first thing to look at is whether its measurement 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, sensors with smaller nonlinear errors can be approximately regarded as linear, which will bring great convenience to the measurement.

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5. Stability

The ability of a sensor to maintain its performance unchanged after being used for a period of time is called stability. The factors that affect the long-term stability of sensors, apart from the structure of the sensors themselves, mainly include the environment in which they are used. Therefore, to ensure that sensors have good stability, they must have strong environmental adaptability.

Before choosing a sensor, an investigation of its usage environment should be conducted, and a suitable sensor should be selected based on the specific usage environment, or appropriate measures should be taken to reduce the impact of the environment.

The stability of sensors has quantitative indicators. After the expiration of their service life, they should be recalibrated before use to determine whether the performance of the sensors has changed. In some situations where sensors are required to be used for a long time and cannot be easily replaced or calibrated, the stability requirements for the selected sensors are stricter, and they must be able to withstand long-term tests.

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6. Precision

Accuracy is an important performance index of sensors and it is a crucial 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 there is no need to choose it too high. In this way, among the many sensors that meet the same measurement purpose, a relatively cheaper and simpler sensor can be selected.

If the measurement purpose is qualitative analysis, a sensor with high repeatability accuracy can be selected; it is not advisable to choose one with high absolute value accuracy. If it is for quantitative analysis and precise measurement values must be obtained, sensors with accuracy grades that meet the requirements should be selected.