Modern sensors are very different in principle and structure, and how to reasonably select sensors according to the specific measurement purpose, measurement object and measurement environment is the first problem to be solved when measuring a certain quantity.
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Once the sensor is determined, the corresponding measurement method and measuring equipment can also be determined. The success or failure of the measurement results depends to a large extent on the selection of the sensor.
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1. Determine the type of sensor according to the measurement object and the measurement environment
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In order to carry out a specific measurement work, it is necessary to first consider the principle of the sensor that should be used, which requires the analysis of many factors.
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Because, even for the measurement of the same physical quantity, there are multiple principles of sensors available, which principle of sensor is more suitable, according to the characteristics of the measurement and the use of the sensor conditions need to consider the following specific issues:
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- the size of the measuring range;
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- The requirements of the measured position for the volume of the sensor;
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- whether the measurement method is contact or non-contact;
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- Signal extraction method, wired or non-contact measurement;
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- The source of the sensor, whether it is domestic or imported, whether the price is affordable, or whether it is self-developed.
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After considering the above questions, it is possible to determine which type of sensor to use, and then consider the specific performance indicators of the sensor.
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Second, the choice of sensitivity
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In general, within the linear range of the sensor, the higher the sensitivity of the sensor, the better. This is because only when the sensitivity is high, the value of the output signal corresponding to the change to be measured 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 that is not related to the measurement is also easy to mix, and will also be amplified by the amplification system, affecting the measurement accuracy. Therefore, it is required that the sensor itself should have a high signal-to-noise ratio to minimize the interference signal introduced from the outside world.
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The sensitivity of the sensor is directional. When the measured quantity is a single vector and its directionality is required to be high, the sensor with low sensitivity in other directions should be selected; If the measurement is a multi-dimensional vector, the smaller the cross-sensitivity of the sensor, the better.
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3. Frequency response characteristics
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The frequency response characteristics of the sensor determine the frequency range to be measured, and the measurement conditions must be maintained without distortion within the allowable frequency range, in fact, there is always a certain delay in the response of the sensor, and the shorter the delay time, the better.
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The frequency response of the sensor is high, and the frequency range of the signal that can be measured is wide, while the inertia of the mechanical system is greater due to the influence of structural characteristics, so the frequency of the signal that can be measured by the sensor with low frequency is low.
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In dynamic measurements, the response characteristics should be based on the characteristics of the signal (steady-state, transient, random, etc.) to avoid excessive errors.
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Fourth, the linear range
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The linear range of a sensor is the range in which the output is proportional to the input. Theoretically, the sensitivity remains constant within this range. The wider the linear range of the sensor, the greater the measuring range and the measurement accuracy. When selecting a sensor, when the type of sensor is determined, the first thing to see is whether its range meets the requirements.
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But in reality, no sensor can guarantee absolute linearity, and its linearity is also relative. When the required measurement accuracy is relatively low, within a certain range, the sensor with small nonlinear error can be approximately regarded as linear, which will bring great convenience to the measurement.
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5. Stability
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The ability of a sensor to remain unchanged after a period of use is called stability. In addition to the structure of the sensor itself, the factors that affect the long-term stability of the sensor are mainly the environment in which the sensor is used. Therefore, in order for the sensor to have good stability, the sensor must have strong environmental adaptability.
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Before selecting a sensor, it is necessary to investigate the environment in which it will be used, and select the appropriate sensor according to the specific environment in which it will be used, or take appropriate measures to reduce the impact of the environment.
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There are quantitative indicators for the stability of the sensor, and after the expiration of the service life, it should be recalibrated before use to determine if the performance of the sensor has changed. In some occasions where the sensor is required to be used for a long time and cannot be easily replaced or calibrated, the stability requirements for the selected sensor are more stringent and can withstand the test for a long time.
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6. Accuracy
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Accuracy 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, so the accuracy of the sensor only needs to meet the accuracy requirements of the entire measurement system, and it is not necessary to choose too high. This makes it possible to choose between a number of sensors that meet the same measurement purpose, which is relatively inexpensive and simple.
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If the purpose of measurement is qualitative analysis, it is sufficient to choose a sensor with high repeatability, and it is not appropriate to choose a sensor with high absolute accuracy; If precise measured values are necessary for quantitative analysis, sensors with the required accuracy class are required.
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For some special use occasions, if the suitable sensor cannot be selected, the sensor needs to be designed and manufactured by itself. The performance of the self-made sensor should meet the requirements of use.
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For any questions such as product consultation, product customization, agency, technical inquiry, quotation, etc., please contact Xingyi Hotline: 400-600-4496!
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