How many common technical parameters of sensors do you know?
Generally refers to the signal range in which the sensor output response drops to one-half of its maximum corresponding square root or half the power. In layman's terms, it is the range that the sensor can sample. The indicator of the sensor's response range to external signals is its bandwidth, which mainly describes the sensor. The dynamic characteristics (whether it can keep up with the changing frequency of the measurement), and the effective bandwidth refers to the bandwidth that the sensor can actually guarantee the measurement accuracy. The bandwidth here is actually described from the frequency domain. In other words, this thing is actually the same thing as frequency response, which is the sensor's ability to respond to external signals! From a transfer function perspective, most sensors can be simplified to a first- or second-order link.
Sensitivity refers to the ratio of the sensor's output change Δy to the input change Δx under steady-state operation.
Generally within the linear range of the sensor, higher sensitivity usually means a higher signal-to-noise ratio of the sensor, and a larger output signal value corresponding to the measured change, which is more conducive to signal processing. However, it should be noted that the sensor has high sensitivity and is easily mixed with external noise unrelated to the measurement, which is then amplified by the amplification system and affects the measurement accuracy. Therefore, it is required that the sensor itself should have a high signal-to-noise ratio to minimize interference signals introduced from the outside.
3. Zero point drift
The sensor input value is zero, and its output value changes to a certain extent, that is, zero point drift. Temperature drift is the most common factor causing zero drift. Causes of zero drift: aging of sensitive components, stress, charge leakage, temperature changes, etc.
Resolution refers to the small changes that the sensor can detect within the specified measurement range. It is the minimum value of the change to be measured that the sensor can detect. For example, using a meter ruler can only measure distances at the millimeter level, while using a micrometer can detect 1/ ‰Millimeter level. Resolution is an absolute value with units. For example, if a temperature sensor has a resolution of 0.1 degrees Celsius and a full-scale range of 500 degrees Celsius, its resolution is 0.1/500=0.02%.
Accuracy refers to the ratio of the value plus or minus three standard deviations near the true value to the measuring range, and refers to the difference between the measured value and the true value. If the purpose of measurement is qualitative analysis, you can choose a sensor with high repeatability accuracy, but you should not choose a sensor with high absolute value accuracy. If it is a measurement value that must be obtained for quantitative analysis, it is necessary to select a sensor with an accuracy that meets the requirements.
(1) Causes of system errors: inherent errors in measurement principles and algorithms, inaccurate calibration, environmental temperature effects, material defects, etc.;
(2) Causes of random errors: transmission clearance, aging of components, etc.
The repeatability of a sensor refers to the difference between measurement results when measurements are repeated multiple times in the same direction under the same conditions. Also known as repetition error, reproduction error, etc. The smaller the repeatability error, the better the repeatability and the better the stability of the sensor.
7. Frequency response characteristics
The frequency response characteristics of the sensor determine the frequency range to be measured, and it must remain undistorted within the allowed frequency range. In fact, there is always a certain delay in the response of the sensor. We hope that the delay time should be as short as possible. Sensors with high frequency response can measure signals in a wide frequency range, but due to the influence of structural characteristics, the inertia of the mechanical system is large, so sensors with low frequency response can measure signals at lower frequencies.
To put it simply, the mapping curves of the input and output of the sensor are inconsistent when the sensor is forward and reverse. This phenomenon is hysteresis. The reasons for hysteresis include: material properties of sensor sensitive components, mechanical structural properties (friction, transmission clearance, etc.), etc.
9. Linear range
The linear range of a sensor is the range over which the output is proportional to the input. Theoretically, within this range, the sensitivity remains unchanged, and the wider the sensor's linear range, the greater its measurement range. But in fact, no sensor can be absolutely linear, and its linearity is relative. When the required measurement accuracy is relatively low, within a certain range, a sensor with a small nonlinear error can be regarded as linear, which facilitates measurement.
10. Sampling frequency
Sampling frequency refers to the number of measurement results that the sensor can sample per unit time, which reflects the sensor's rapid response capability. Sampling frequency is a technical indicator that must be fully considered when measurement data changes rapidly.
As the sampling frequency is different, the accuracy index of the sensor also changes. Generally speaking, the higher the sampling frequency, the lower the measurement accuracy. However, the accuracy given by the sensor is often a measurement result obtained at the sampling speed or even under static conditions. Therefore, both accuracy and speed must be considered when selecting a sensor.
Review Editor: Liu Qing
#common #technical #parameters #sensors
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