The reliability index of the pressure sensor test process changes with the design modification, the different use conditions and the performance degradation in the working process. Therefore, it must be considered from many aspects.

Specify the conditions of use

Any product is developed in accordance with the prescribed conditions of use. This service condition includes working conditions (such as functional mode, operation mode, load conditions, working energy, maintenance conditions, etc.) and environmental conditions (such as temperature, humidity, air pressure, vibration, etc.). The reliability of the same product is different under different working conditions and environmental conditions. Devices that test pressure sensors are no exception.

The environmental conditions that affect the reliability of the testing process generally include the following: climatic environmental conditions, mechanical environmental conditions, biological conditions, chemical conditions, electrical and electromagnetic conditions, radiation conditions, system connection conditions and human factors. Here we mainly consider the climatic and environmental conditions, chemical conditions and system connection conditions. The climatic and environmental conditions include temperature, humidity, air pressure, wind, rain, frost and dust, etc. Chemical conditions include factors such as the instability of the power supply, interference signals from the conductive line system, interference from electromagnetic fields and lightning, corona and discharge. System connection conditions include factors such as connections between functional units within a large system, a system or a device connected to other devices for use. The above three factors all have an impact on the reliability of equipment, but the degree of influence of various factors on different equipment is not the same.

Time of use

The reliability of sensor test equipment is a function of time, and it decreases with the passage of time. Even if the components have been screened and the whole machine has been aging and maintained, the failure efficiency of the equipment in the case of accidental failure zone is a constant within this period of time. However, the distribution of equipment over time conforms to the law shown in FIG. 5, that is, the longer it is used, the lower the reliability of the test equipment will be.

The function that can be achieved

The so-called "function" is the product's main performance indicators and technical requirements. This is the product to complete the prescribed tasks and role of the guarantee. The so-called product is not reliable, in terms of the adequacy of the product to meet the specified performance indicators and technical requirements. The higher the performance indicators and technical requirements of the product, the smaller the range of allowable changes, the less likely the product is to fulfill the "specified function", and the lower the reliability level of the product. On the contrary, the lower the performance index and technical requirements of the product, the wider the range of allowable changes, the more likely the product can complete the "specified function", and the higher the reliability level of the product will be. For the sensor test equipment, the higher the requirement for the sensor test precision, the lower the reliability level, but the more real the sensor data can be measured by the test equipment. On the contrary, if the test accuracy of the pressure sensor is lower, then the reliability level of the equipment will be higher, but its influence on obtaining the real data of the sensor will be greater.

It should also be pointed out in particular that, from the point of view of the use of test equipment, the most important indicator of the equipment is the reliability index on the premise that the basic performance index meets the use requirements. If the device is unreliable, unstable, and often broken, the initial performance of the test device is of no practical significance, let alone getting real data from the sensor.

Reliability analysis

Assumes that under a certain confidence value, the reliability of the pressure source for R1 (t), environment provide equipment reliability for R2 (t), the reliability of the measurement circuit for R3 (t), the reliability of the power supply system for R4 (t), then get the reliability of the sensor data R (t) and necessarily R1 (t), R2 (t), R3 (t), R4 (t), namely

R (t) =f[R1 (t), R2 (t), R3 (t), R4 (t)] (7)

It can be seen from the measurement system in Equation (7) and FIG. 4

R of t is equal to K, right? R1 (t)? R2 of t, right? R3 of t, right? R4 (t) (8)

Where, K is a coefficient, which is closely related to the service time and conditions of various equipment.

Now take the sensor test of our unit as an example: under the same other test conditions, 10 uncompensated pressure sensors were tested at zero point using two different environmental equipment.

In the case that other conditions are identical and different temperature boxes are used, different test results will be obtained. However, the most important thing for us is to determine which set of data is more reliable, which is closer to the real data of sensor performance. It can be seen from Table 1 that the thermostat of # 1 has been working for nearly two years, and the thermostat of # 2 has been working for more than ten years. According to the distribution law of equipment reliability over time, the reliability of No. 1 equipment is higher than that of No. 2 equipment. Therefore, the sensor data measured with 1# device is more reliable.

Measures to increase the reliability of the test process

(1) Strengthen the pressure sensor test equipment management, regular overhaul and maintenance, on the basis of performance to meet the conditions, improve the service life of the equipment.

(2) Strictly control the temperature, humidity, cleanliness and other environmental conditions of the test site; Shorten the turnaround time between processes and improve the testing efficiency of sensors.

(3) Regularly test and calibrate all kinds of verification equipment, to ensure that the performance of testing equipment to meet the requirements of sensor testing, so as to ensure the reliability of the obtained test data.

(4) Insist on the sensor test data summary, calculation and analysis, find out the factors affecting the sensor output during the test process, and to solve, to improve the quality of the sensor products to lay a solid foundation.