Characteristics Of Sensors

Sensor dynamics
The so-called dynamic characteristics refer to the output characteristics of a sensor when its input changes. In practical work, the dynamic characteristics of sensors are often represented by their response to certain standard input signals. This is because the response of the sensor to the standard input signal is easily obtained through experimental methods, and there is a certain relationship between its response to the standard input signal and its response to any input signal. Often, knowing the former can infer the latter. The most commonly used standard input signals are step signal and sine signal, so the dynamic characteristics of sensors are also commonly represented by step response and frequency response.
Linearity
Usually, the actual static characteristic output of a sensor is a curve rather than a straight line. In practical work, in order to ensure that the instrument has a uniform scale reading, a fitted straight line is commonly used to approximate the actual characteristic curve, and linearity (nonlinear error) is a performance indicator of this approximation degree.
There are multiple methods for selecting fitting straight lines. If the theoretical straight line connecting the zero input and full scale output points is used as the fitting straight line; Alternatively, the theoretical line with the smallest sum of squares of the deviations from each point on the characteristic curve can be used as a fitting line, which is called the least squares fitting line.
sensitivity
Sensitivity refers to the ratio of the output change △ y of a sensor to the input change △ x under steady-state operating conditions.
It is the slope of the output input characteristic curve. If there is a linear relationship between the output and input of the sensor, then the sensitivity S is a constant. Otherwise, it will vary with the input quantity.
The dimension of sensitivity is the ratio of output to input dimensions. For example, if the output voltage of a displacement sensor changes to 200mV when the displacement changes by 1mm, its sensitivity should be expressed as 200mV/mm.
When the dimensions of the output and input of the sensor are the same, sensitivity can be understood as amplification factor.
Improving sensitivity can achieve high measurement accuracy. But the higher the sensitivity, the narrower the measurement range, and the worse the stability.
resolving power
Resolution refers to the ability of a sensor to sense the smallest change in the measured value. That is to say, if the input quantity slowly changes from a non-zero value. When the input change value does not exceed a certain value, the output of the sensor will not change, that is, the sensor cannot distinguish the change in this input quantity. The output will only change when the change in input exceeds the resolution.
Usually, the resolution of each point in the full scale range of a sensor is not the same, so the maximum change value of the input quantity that can cause a step change in the output quantity in the full scale is commonly used as an indicator to measure resolution. If the above indicators are expressed as a percentage of full scale, they are called resolution. There is a negative correlation between resolution and sensor stability.