Automobile fault diagnostic instrument

Abstract

The invention relates to an automobile fault diagnostic instrument, comprising an MCU control module, a front end multimeter measurement module for measuring the received voltage and the resistance and transmitting the measurement result to the MCU control module, an impedance transform module for switching the input impedance to realize the cable testing function, a display module for displaying the measurement result, and a buzzer alarm module for achieving the sound alarm prompt. The MCU control module can judge whether an AC signal or a PWM signal component is included or not by performing AD conversion acquisition analysis directly on an input DC signal. The MCU control module can also realize the cable test function by controlling the impedance conversion module to switch the input circuit to the constant current load mode, that is, to switch the input impedance to judge the amplitude of the input voltage drop. In addition to the basic functions of measuring the voltage and the resistance of the multimeter, the instrument integrates the function of alarming and indicating AC and PWM signals in the DC signal, and also has the cable performance testing function.

Description

technical field [0001] The invention relates to an automobile fault diagnosis instrument. Background technique [0002] The alternator of the car is powered by three phases, and there is a set of rectifiers inside that can rectify the three-phase alternating current into direct current for use by the equipment. If the rectifier is aging, the rectified DC power may be impure and contain AC signals, which will affect the normal operation of the battery or electronic equipment in the car, and ordinary multimeters cannot identify the AC component of the DC signal. Many devices in the car are driven by PWM signals. If you use an ordinary multimeter to measure the PWM signal line, there may be strange readings, which will affect the technician's judgment on the fault. If the switches or connectors of certain equipment in the car have poor contact, etc., the impedance of the cable may increase, resulting in an increase in voltage drop, which will affect the power supply system dur...

AI Technical Summary

Problems solved by technology

If the rectifier is aging, it may make the rectified DC impure and contain AC signals, which will affect the normal operation of the battery or electronic equipment in the car, and ordinary multimeters cannot identify the AC component of the DC signal.

Many devices in the car are driven by PWM signals. If you use an ordinary multimeter to measure the PWM signal line, there may be strange readings, which will affect the technician's judgment on the fault.

If the switches or connectors of some equipment in the car have poor contact, etc., the impedance of the cable may increase, resulting in an increase in voltage drop, which will affect the power supply system during work, and make the equipment in the car work abnormally. , but because the connection between the cable and the connector may only be poor and not completely disconnected, it is difficult to find the problem with the conventional multimeter measurement method

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