Proper selection of sensors

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Modern sensors vary greatly in principle and structure. How to select the appropriate sensor based on the specific measurement objectives, the object being measured, and the measurement environment is the first issue that needs to be addressed when carrying out a measurement of a certain quantity. Once the sensor is determined, the corresponding measurement methods and equipment can also be identified. The success or failure of the measurement results depends to a large extent on whether the appropriate sensor has been selected. 1. Selection of sensitivity: Generally, within the linear range of a sensor, it is desirable for the sensor to have higher sensitivity. Because only when the sensitivity is high is the value of the output signal corresponding to changes in the quantity being measured relatively large, which facilitates signal processing. It should be noted, however, that due to the high sensitivity of the sensor, external noises unrelated to the quantity being measured can easily mix in and be amplified by the amplification system, thereby affecting the measurement accuracy. Therefore, the sensor itself is required to have a high signal-to-noise ratio in order to minimize interference signals introduced from the outside. The sensitivity of the sensor is directional. When the quantity being measured is a unidirectional vector and high requirements are placed on its directionality, sensors with low sensitivity in other directions should be selected ； If the quantity being measured is a multidimensional vector, it is desirable that the cross-sensitivity of the sensor be as low as possible. 2. Determine the type of sensor based on the object being measured and the measurement environment. To carry out a specific measurement task, it is first necessary to consider what principle the sensor should be based on, and this decision can only be made after analyzing various factors. Because, even when measuring the same physical quantity, there are various types of sensors based on different principles available. To determine which principle is most suitable, it is necessary to consider certain specific factors related to the characteristics of the quantity being measured as well as the conditions under which the sensor will be used: the range of measurement ； Requirements of the measurement location on sensor size ； Is the measurement method contact-based or non-contact? ； Methods for extracting signals, wired or contactless measurement ； The source of the sensors: domestic or imported? Is the price affordable, or should they be developed in-house? After considering the above issues, it is possible to determine which type of sensor to use, and then consider the specific performance parameters of that sensor. 3. Frequency response characteristics: The frequency response characteristics of a sensor determine the frequency range of the quantities that can be measured. It is necessary to maintain undistorted measurement conditions within the allowable frequency range. In practice, there is always a certain delay in the sensor’s response, and it is desirable for this delay to be as short as possible. A sensor with a high frequency response enables measurement over a wide range of signal frequencies. However, due to the influence of structural characteristics, mechanical systems have considerable inertia, which results in sensors being capable of detecting signals at lower frequencies. In dynamic measurements, the response characteristics should be adjusted according to the properties of the signal (steady-state, transient, random, etc.) in order to avoid excessive errors. 4. Linear range: The linear range of a sensor refers to the range within which the output is proportional to the input. Theoretically, within this range, the sensitivity remains constant. The wider the linear range of a sensor, the greater its measurement range, and it can ensure a certain level of measurement accuracy. When selecting a sensor, once the type of sensor has been determined, the first thing to check is whether its range meets the requirements. But in reality, no sensor can guarantee absolute linearity; its linearity is also relative. When the required measurement accuracy is relatively low, within a certain range, sensors with low nonlinear errors can be approximated as linear, which greatly facilitates measurement. 5. Stability: The ability of a sensor to maintain its performance unchanged after being used for a certain period of time is referred to as stability. Apart from the sensor’s own structure, the factors that affect its long-term stability are mainly the operating environment in which the sensor is used. Therefore, to ensure good stability of the sensor, it must have a strong ability to adapt to its environment. Before selecting a sensor, its operating environment should be investigated, and an appropriate sensor should be chosen based on that specific environment, or appropriate measures should be taken to reduce the impact of the environment. There are quantitative indicators for the stability of sensors; after exceeding their service life, they should be recalibrated before use to determine whether their performance has changed.