Sensor selection method – ifm

Modern sensors are very different in principle and structure, how to reasonably select sensors according to the detailed measurement intention, measurement objectives and measurement environment, is the first problem to deal with when carrying out a certain quantity measurement.

When the sensor is confirmed, the corresponding measurement method and measurement equipment can also be confirmed. The success or failure of the measurement results depends to a large extent on whether the selection of sensors is reasonable.

Sensor selection method – ifm

1. Confirm the type of sensor according to the measurement target and measurement environment

In order to carry out a detailed measurement operation, it is necessary to first consider what kind of sensor principle should be used, which needs to be confirmed after analyzing many factors.

Because, even if the same physical quantity is measured, there are multiple principles of sensors to choose from, which principle of the sensor is more suitable, then the following detailed questions need to be considered according to the characteristics of the measurement and the application conditions of the sensor:

(1) The size of the measuring range;

(2) the requirements of the measured position on the volume of the sensor;

(3) The measurement method is touch type or right or wrong touch type;

(4) The method of signal elicitation, wired or right and wrong touch measurement;

(5) The origin of the sensor, domestic or imported, whether the price is acceptable, or self-developed. After considering the above questions, it is possible to determine the type of sensor to use, and then consider the detailed functional indicators of the sensor.

2. Selection of sensitivity

In general, within the linear scale of the sensor, the higher the desired 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 the external noise that is not related to the measurement is also easy to mix, and it will also be amplified by the amplification system, which will affect the measurement accuracy. Therefore, it is required that the sensor itself should have a high signal-to-noise ratio to minimize the introduction of disturbance signals from the outside world.

The sensitivity of the sensor is directional. When the measured quantity is a one-vector quantity and has high requirements for its directionality, 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.

3. Frequency echo characteristics

The frequency echo characteristics of the sensor determine the frequency scale to be measured, and the measurement condition of non-distortion must be adhered to within the allowable frequency scale, in fact, the response of the sensor always has a certain delay, and the shorter the delay time, the better.

The frequency response of the sensor is high, and the frequency scale of the measurable signal is wide, and because of the influence of structural characteristics, the inertia of the mechanical system is large, so the frequency of the measurable signal of the sensor with low frequency is low.

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

4. Linear scale

The linear scale of a sensor refers to the scale at which the output is proportional to the input. Theoretically, the sensitivity sticks to a fixed value within this scale. The wider the linear scale of the sensor, the greater its measuring range and the guaranteed measurement accuracy. When selecting a sensor, when the variety of the sensor is confirmed, the first thing to see is whether its range meets the requirements.

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 scale, the sensor with small nonlinear error can be approximately regarded as linear, which will bring great convenience to the measurement.

5. Stability

The ability of a sensor to persist in its function without changing 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 operating 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, it is necessary to investigate the environment in which it will be used, and select the appropriate sensor based on the detailed application environment, or take appropriate measures to reduce the impact of the environment.

There are quantitative indicators for the stability of the sensor, and after the service period has expired, it should be recalibrated before use to confirm whether the function 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 long-term detection.

6. Precision

Accuracy is an important functional index of the sensor, and it is an important 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 too high. In this way, it is possible to choose the cheaper and simpler sensor among the many sensors that are satisfied with the same measurement intent.

If the measurement intention 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 measurement accuracy; If it is necessary to obtain accurate measurements for quantitative analysis, it is necessary to select a sensor with an accuracy level that satisfies the requirements

Sensor selection method – ifm

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