Research on reliability of dual potentiometer.hf preselector

　　When the dual potentiometer rotates, there are four states: pin 3 is connected with pin 1, pin 3 is fully connected with pin 2 and pin 1; Pin 3 is connected to pin 2, and pin 3 is completely disconnected from pin 2 and pin 1.

　　In practical use, pin 3 grounding is generally used as the data input end. As the reliability of pins 1 and 2, the research data output terminal is connected with the I/O port of the single chip microcomputer. As shown in Figure 2, pin 1 is connected to P1.0 of the microcontroller, and pin 2 is connected to P1.1 of the microcontroller. When the dual potentiometer is rotated left or right, P1.0 and P1.1 will periodically double the potentiometer to produce the waveform shown in Figure 1, if it is 12 points of the dual potentiometer rotation will produce 12 groups of such waveform, 24 points of the dual potentiometer will produce 24 groups of such waveform

　　The component reliability problem is the basic failure rate problem, which is a random quality failure, and the difference between the quality problem is that the failure rate of the component depends on the working stress level. At a certain stress level, the failure rate of components will be greatly reduced. In order to eliminate components that do not meet the requirements of use, including electrical parameter reliability, research failure, sealing performance failure, appearance failure, poor stability, early failure, etc., screening tests should be carried out, which is reliability, research a non-destructive test. Through screening, the failure rate of components can be reduced by 1 to 2 orders of magnitude, of course, the cost of screening tests (time and cost) is very large, but comprehensive maintenance, logistics support, the whole dual potentiometer joint test is still cost-effective, and the development cycle will not be extended. General requirements for screening tests of main components of power equipment:

　　① Resistance is 100% tested at room temperature according to technical conditions, and unqualified products are removed.

　　② Ordinary capacitors are 100% tested at room temperature according to technical conditions, and unqualified products are removed.

　　③ Connectors are sampled to detect various parameters according to technical conditions.

　　④ Semiconductor devices are screened according to the following procedures:

　　Visual inspection  primary test  high temperature storage  high and low temperature shock  power reliability, aging study  high temperature test  low temperature test  normal temperature test

　　After screening, the exclusion rate should be calculated in formula Q: N -- the total number of tested samples; n -- the number of samples removed;

　　If Q exceeds the upper limit specified in the standard, all the components in this batch are not allowed to be on the machine and are processed according to the relevant provisions.

　　In compliance with the standard provisions, the qualified components will be marked with paint points, and then into the special warehouse for installation.

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