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Sensor Test Sensor Detection Technology-Technical Explanation

Sensor Test Sensor Detection Technology-Technical Explanation

November 20 , 2023 0

The detection of sensor quality mainly includes the basic characteristic detection technology and reliability test technology of the sensor. Converting all kinds of information into electricity is the basic characteristic of sensor. The method to describe the basic characteristics of the sensor includes mathematical model and basic characteristics index, which can be divided into static characteristics and dynamic characteristics according to the input of the sensor. Static characteristic refers to a relationship that describes the input and output quality inspection of a sensor under the action of static signals. The dynamic characteristic is the response (output) characteristic of the sensor to the dynamic excitation (input), that is, the response characteristic of its output to the amount of input that changes with time.

I. Classification OF Sensors

According to the technical characteristics of the sensor, the detection technology is mainly divided into basic parameter detection technology, environmental parameter detection technology, reliability detection technology and other index detection technology.

1.1 Basic Parameter Detection Items

Range: range range, overload capacity
Sensitivity: sensitivity, resolution, input and output impedance accuracy: accuracy, repeatability, linearity, hysteresis, sensitivity error Min, stability, drift
Dynamic performance: natural frequency, damping coefficient, frequency response range, frequency characteristics, time constant, rise time, response time, overimpulse, add-subtract rate, steady state error, critical speed, critical frequency, etc

1.2 Environmental Parameter Detection Items

Temperature: operating temperature range, temperature drift, thermal lag
Shock resistance: vibration, shock, drop, acceleration
Other environmental aspects: damp heat resistance to medium corrosion, electromagnetic compatibility, IP test

1.3 Reliability Test Item

Working life
reliability
Mean time without failure
Insurance period
Fatigue performance
Insulation resistance
Voltage resistance

II. Test Items And Test Methods

2.1 Accuracy Test

Refers to the reliability of the measurement results, the smaller the measurement error, the higher the accuracy of the sensor. The accuracy of the sensor is expressed by the percentage of the maximum basic error in its range and the ratio of the full scale output. The basic error is the measurement error of the sensor under the specified normal working conditions, which is composed of two parts: systematic error and random error. In engineering technology, the precision grade is quoted in order to simplify the representation of the sensor accuracy. Accuracy grade to standard
Percentile represents the maximum allowable error of the sensor measurement. Detection method :@ The sensor range is divided into a number of equal spacing points :0 according to the points, input the standard value one by one from small to large, and record the corresponding output value of each input value; After reaching the input upper limit, the standard value is entered one by one from large to small, and the output value corresponding to each input value is recorded; 0 According to the process described in 0, the sensor is repeatedly measured for no less than three times, 0 the measurement data is processed, and the nonlinear, hysteresis, repeatability, sensitivity, accuracy and other characteristics of the sensor are determined according to the processing results.
Data processing methods generally include zero base line method, end base line method and least square method

2.2 Stability Test

Represents the ability of the sensor to maintain its performance parameters over an extended period of time. Over time, the characteristics of most sensors change. This is because the characteristics of the sensor, or the components that make up the sensor, change over time, which affects the stability of the sensor.
Detection method: Under stable temperature, humidity and other environmental conditions, the output value of the sensor is tested at a certain time interval (generally zero output value or full scale output short-time stability test time is recommended for 24 hours, 48 hours, 72 hours, 96 hours, 120 hours). The recommended duration of long-term stability test is 28 days, 56 days, 84 days, 168 days, 336 days. The maximum value of the output value change rate must meet the requirements of the sensor technical specifications. The stability error can be expressed by relative error or absolute error.

2.3 Drift Test

Drift refers to the phenomenon that the output of the sensor changes with time when the input quantity is unchanged. There are two reasons for drift: @sensor's own structural parameters change, @) changes in the surrounding environment (such as temperature, humidity, etc.), the most common is temperature drift, that is, changes in ambient temperature cause changes in the output, and temperature drift is mainly manifested
Temperature drift Temperature drift is usually the ratio of the change in the output value of the sensor when the operating environment temperature deviates from the standard environment temperature (generally 20) to the change in temperature. The detection includes sensor zero drift and sensor sensitivity drift. For non-temperature sensors, taking temperature as a parameter, the sensor is measured at zero output and full scale output at temperature operation 1 and operation, respectively. Generally, the sensor is measured three times, and the average value of the date point output and full scale output is calculated. The zero output and sensitivity of the sensor at temperature 1, 5 can be calculated, and the temperature drift of the sensor can be obtained.

2.4 Impact Measurement

The amount caused by changes in the external environment is called the influence amount, which is caused by external environmental influences such as temperature, humidity, air pressure, vibration, power supply voltage and power supply frequency. When indicating the influence amount, it is necessary to express the influence factors and the deviation of the output value at the same time. If the output value of a sensor changes by 0.02 millivolts due to a 10° temperature change, it should be written as 0.02 millivolts /10°C.
The impact test items include temperature effect, vibration effect, shock effect, acceleration effect, wet heat effect, salt spray effect, thermal radiation effect, low pressure effect, low temperature/low pressure combined effect, high temperature/low pressure combined effect, low temperature/low pressure/wet heat combined effect, dust effect, noise effect, electromagnetic compatibility.
Temperature influence tests were conducted according to GB/T 2423.1-2008 and GB/T 2423.2-2008. The vibration effect test was carried out according to GB/T 2423.10-2008; The impact impact test was conducted according to GB/T 2423.5-1995, the acceleration impact test was conducted according to GB/T 2423.15-2008, and the moisture and heat impact test was conducted according to GB/T 2423.3-2006, and the salt spray impact test was conducted according to GB/T 2423.17-2008. The thermal emission effect test was conducted according to GB/T 2423.24-2013. Low pressure impact test according to GB/T 2423.21.2008: low temperature/low pressure comprehensive impact test according to GB/T 2423.25-2008; The combined effect test of high temperature/low pressure was conducted according to GB/T 2423.26-2008. The combined effect test of low temperature/low pressure/humid heat was conducted according to GB/T 2423.27-2005. Dust impact test GB/T 2423.37-2006: Noise impact test according to GJB150.17A-2009: electromagnetic compatibility test according to GB/T 1726 "Electromagnetic Compatibility test and measurement Technology".

2.5 Dynamic Performance Test

The relationship between the output and input of a sensor when its input is a signal that varies with time. The performance indexes of the main dynamic characteristics are the time domain unit step response performance indexes.
Frequency domain frequency characteristic performance indicators.
Detection method: When the sensor is in a steady state, the typical input signal is applied to it, so that the steady state of the sensor is destroyed and the output value changes until the establishment of the down-steady state, and the whole change process is recorded with an oscilloscope or recorder. By analyzing the recorded graphs and curves, the data of dynamic performance index are obtained. Typical input signals include unit step function, unit ramp function, unit acceleration function (parabolic function), unit pulse function, and sinusoidal signal.

2.6 Reliability Test

The ability or possibility to perform the specified function without fault in a certain time and under certain conditions can evaluate the reliability of the sensor by reliability, failure rate, average trouble-free interval, etc.
Sensor reliability test classification methods are generally divided into four types: @ divided by environmental conditions, including simulated tests and field tests under various stress conditions, @ divided by test items, including environmental tests, life tests, accelerated tests and various special tests; @ According to the purpose of the test, including screening test, identification test and acceptance test; 0 Divided by the nature of the test, including destructive test and non-destructive test two categories. Generally, the classification method includes environmental test, life test, screening test, field use test and identification test.
In order to confirm the normal operation of the sensor in the application environment, the product is required to simulate some detection items. It mainly includes high temperature test, low temperature test, high and low temperature alternating test, high temperature and high humidity test, mechanical vibration test, mechanical impact test, electric on-off test, power supply influence test, cold start test, salt test, rain test, dust test reliability test according to GB/T 29309-2012 "Accelerated Stress Test Procedures for Electrical and electronic Products" high accelerated life test guidelines, the standard specifies the general requirements of high accelerated life test, test preparation and test methods. In the specified high accelerated life test, the applied test stress includes high temperature step, low temperature step, fast temperature change cycle, six degrees of freedom non-Gaussian broadband random vibration and so on

III.The Development Trend OF Sensor Detection

It mainly includes the application of precision test technology and extreme test. Including high performance test equipment such as high performance laser test system, scanning micro measurement technology, scanning X-ray interferometry and other technologies. Research on on-line testing and digital testing technology. It includes on-line testing technology, robot testing technology, networked multi-sensor testing and testing information fusion technology. System integration technology in computer network environment directly affects the scope and level of application of instrumentation and test control science and technology. Computer vision testing skills are not. It is an optical testing method combining computer vision, image processing and testing technology. It has the advantages of non-contact, real-time on-line, high precision and abundant information. The innovation of new sensing principles and the development of new technologies to promote testing. For example, based on MEMS process integrated multi-parameter sensor, high temperature pressure sensor, micro inertial sensor, optical fiber sensor detection technology. Virtual testing technology and virtual instrument development.