Characteristics and performance parameters of the sensor

Sensor static characteristics

static characteristic , It refers to when the input of the detection system is a constant signal that does not change with time , The relationship between the output and input of the system . Mainly including linearity 、 sensitivity 、 Hysteresis 、 Repeatability 、 Drift, etc .

• Linearity
  The degree of deviation between the sensor input and the actual output curve .

• sensitivity
  Sensitivity is an important index of the static characteristics of the sensor . It is defined as the increment of output Δy And the corresponding input increment that causes this increment Δx The ratio of the . It represents the change of sensor output caused by the change of unit input , obviously , sensitivity S The bigger the value is. , Indicates that the sensor is more sensitive .

• Hysteresis
  The input of the sensor increases from small to large ( Positive stroke ) And input from large to small ( Reverse stroke ) The phenomenon that the input and output characteristic curves do not coincide during the change is called hysteresis .

• Repeatability
  Repeatability means that the sensor changes continuously in the same direction for multiple times , The degree of inconsistency of the obtained characteristic curve .

• drift
  The drift of the sensor means that when the input is constant , The output of the sensor changes with time , This phenomenon is called drift . There are two reasons for drift ： First, the structural parameters of the sensor itself ; Second, the surrounding environment ( Such as temperature 、 Humidity, etc ). The most common drift is temperature drift , That is, the change of output caused by the change of ambient temperature , Temperature drift is mainly represented by temperature zero drift and temperature sensitivity drift .

• measuring range
  The minimum input that the sensor can measure , The range between and the maximum input is called the measurement range of the sensor .

• range
  Algebraic difference between the upper limit value and the lower limit value of the sensor measurement range , Called range .

• precision
  The accuracy of the sensor refers to the reliability of the measurement results , It is a comprehensive reflection of various errors in measurement , The smaller the measurement error , The higher the accuracy of the sensor .

• Resolution and threshold
  The ability of a sensor to detect the smallest change in input is called resolution .

• stability
  Stability represents the ability of a sensor to maintain its performance parameters over a long period of time . The ideal situation is whenever , The characteristic parameters of the sensor do not change with time . But actually , as time goes on , The characteristics of most sensors will change . This is because of the sensitive elements or components that make up the sensor , Its characteristics change over time , Thus affecting the stability of the sensor .
  

Sensor dynamic characteristics

Dynamic characteristics , When the input of the sensor changes , The characteristics of its output . In practice , The dynamic characteristics of the sensor are often expressed by its response to some standard input signals . The most commonly used standard input signals are step signal and sinusoidal signal , Therefore, the dynamic characteristics of sensors are often expressed by step response and frequency response .

• Dynamic range
  Dynamic range is the measuring range , It means that the variation of sensitivity with amplitude does not exceed the amplitude range of the input mechanical quantity of the given error . In this context , The output voltage is proportional to the mechanical input , So it is also called linear range .

• threshold
  That is, the resolution near zero , In other words, it refers to the minimum measured input value that can make the output of the sensor produce measurable changes .

• drift
  It refers to that the output of the sensor has something independent of the measured input in a certain time interval 、 Unnecessary changes . Including zero drift and sensitivity drift .

• phase shift
  When inputting simple harmonic vibration , The phase lag of the output voltage signal with the same frequency relative to the input . The existence of phase shift may cause the output synthetic waveform to change , To avoid output distortion , The phase shift value is required to be zero or π, Or it changes in direct proportion to the frequency .

• Use frequency range
  It means that the magnitude of sensitivity changing with frequency does not exceed the frequency range of the given error . Its two ends are the lower limit and upper limit of frequency . In order to measure static mechanical quantity , The sensor shall have zero frequency response characteristics . The frequency range of the sensor , In addition to the frequency response characteristics of the sensor itself , It is also related to the installation conditions of the sensor （ It mainly affects the upper limit of frequency ）.

• stability
  It refers to the ability of the sensor to maintain its performance within a specific time .

• Repeatability
  It refers to the output obtained from the continuous repeated measurement of the sensor input in the same direction in the full range / The degree to which input characteristic curves are inconsistent . The main reason for the inconsistency is that the mechanical part of the sensor inevitably has spacing 、 Friction and looseness .

• reliability
  It usually includes working life 、 Mean time between failures 、 Fatigue performance 、 Insulation resistance 、 Withstand voltage and other indicators .