What are the main static characteristics of the sensor

Static characteristics refers to the detection of the input of the system for the constant signal does not change over time, the relationship between the output of the system and the input. Mainly includes linearity, sensitivity, hysteresis, repeatability, drift and so on.

(1) Linearity

refers to the degree to which the actual relationship curve between the sensor output and input deviates from the fitted straight line.

(2) Sensitivity

Sensitivity is an important indicator of the static characteristics of the sensor. It is defined as the incremental output Δy with the corresponding input increment caused by the incremental Δx ratio. It represents the change in unit input caused by the change in sensor output, obviously, the greater the value of sensitivity S, that the sensor is more sensitive.

(3) hysteresis

Sensor in the input quantity from small to large (positive stroke) and the input quantity from large to small (anti-stroke) during the change in the input and output characteristic curve does not overlap the phenomenon known as hysteresis. That is, for the same size of the input signal, the sensor's positive and negative stroke output signal size is not equal, the difference is called hysteresis difference.

(4) Repeatability

Repeatability refers to the sensor in the same direction of the input for the full range of many consecutive changes, the degree of inconsistency of the characteristic curve.

(5) Drift

The drift of the sensor is the input quantity is unchanged, the sensor output changes over time, this phenomenon is called drift. There are two reasons for drift: one is the sensor's own structural parameters; the second is the surrounding environment (such as temperature, humidity, etc.). The most common drift is temperature drift, that is, the surrounding environment temperature changes caused by changes in output, temperature drift is mainly manifested in the temperature zero drift and temperature sensitivity drift.

Temperature drift is usually used to sensor working environment temperature deviation from the standard ambient temperature (generally 20 ℃) when the amount of change in the output value of the amount of change with the ratio of the temperature change

(6) Measuring range (measuring range)

Sensor can be measured to the smallest amount of input and the maximum amount of input between the range is called the sensor's measuring range.

(7) range (span)

The algebraic difference between the upper and lower limits of the sensor's measuring range is called the range.

(8) accuracy (accuracy)

The accuracy of the sensor refers to the degree of reliability of the measurement results, is the measurement of various types of errors in the integrated reflection, the smaller the measurement error, the higher the accuracy of the sensor.

The accuracy of the sensor with its range range of the maximum basic error and the full range of the output ratio of the percentage of the basic error is the sensor in the specified normal operating conditions of the measurement error, by the systematic error and random error of the two parts

Engineering technology in order to simplify the representation of the sensor accuracy, quoted in the concept of the accuracy level. Accuracy level to a series of standardized percentage values expressed in steps, representing the sensor measurement of the maximum allowable error.

If the sensor's operating conditions deviate from the normal operating conditions, it will also bring additional errors, the temperature additional error is the most important additional error.

(9) resolution and threshold (resolution and threshold)

The ability of the sensor to detect the smallest change in the input is called resolution. For some sensors, such as potentiometer sensors, when the input quantity changes continuously, the output quantity is only a step change, the resolution is the output quantity of each "step" represents the size of the input quantity. For digital instruments, the resolving power is the last digit of the indicated value of the instrument represents the value. When the measured change is less than the resolving power, the last digit of the digital meter remains unchanged and still indicates the original value. When the resolving power to the full-scale output of the percentage is called resolution.

Threshold is the smallest measured input value that can produce a measurable amount of change at the output of the sensor, i.e., the resolving power near zero. Some sensors have serious nonlinearities near zero, forming the so-called "dead zone" (dead band), the size of the dead zone as the threshold; more often, the threshold depends mainly on the size of the sensor noise, and thus some sensors only give the noise level.

(10) Stability (stability)

Stability indicates the ability of the sensor to maintain its performance parameters over a long period of time. Ideally, no matter what time of day, the sensor's characteristic parameters do not change over time. In practice, however, the characteristics of most sensors change over time. This is because the sensitive elements, or components that make up the sensor, change their characteristics over time, which affects the stability of the sensor.

Stability is generally expressed in terms of the difference between the output of the sensor and the output of the starting calibration after a specified time interval at room temperature, and is called the stability error. Stability error can be expressed in terms of relative error or absolute error.