How to use a multimeter to test and detect electrical faults
How to use it to test and detect faults has always been a difficult task, because it is difficult to capture the electrical parameters when faults occur, which adds great difficulty to our detection.
There are many testing devices that can make intermittent fault diagnosis simple. These devices include complex signal analyzers and digital devices, as well as easy-to-use handheld multimeters and digital multimeters. In terms of basic measurement functions (AC voltage, DC voltage, and resistance measurement), they also require measurement recording capabilities. By combining standard tables, the multimeter can detect the fault parameters of intermittent faults.
In the past, people used mechanical paper tape recorders to continuously record voltage or current. During operation, it was necessary to connect voltage to the input or clamp the current on the wire. The recorder would print the changes in voltage or current on the paper tape, and the maximum length of the record depended on the amount of paper on the paper slide.
How to record intermittent faults with a multimeter
Use the minimum/maximum/average value recording mode of the multimeter, select the corresponding power (AC voltage, DC voltage, resistance, AC current, DC current, and frequency) according to the measurement item, ensure that the test circuit is connected before activating the minimum/maximum/average value function, otherwise the minimum value reading will always be the environmental value before the test line is connected. This will affect the analysis of the recorded data after the end of the recording time. Activate the minimum/maximum/average value recording mode, and the multimeter display will indicate the maximum reading. When a new maximum or minimum value is detected, a buzzing sound will be emitted.
The advantage of this is that, while ensuring that the digital multimeter is not tampered with and poses no safety hazards to anyone, it can be left in place for measurement and focused on other tasks. At any time during the recording cycle, you can view the saved readings or pause the recording mode without deleting the saved readings.
How to continuously record intermittent faults with a multimeter
Some multimeters not only have the function of recording minimum/maximum/average values, but also combine this function with another function called AutoHOLD and larger memory, forming the power of Event Logging. Automatic maintenance can sense when the measurement signal becomes unstable and when it stabilizes again. By using the auto hold function to trigger the start and stop of the minimum/maximum value recording function, the digital multimeter is not limited to detecting faults that generate minimum or maximum values.
If the multimeter has an infrared RS232 interface, the continuous recording function will be more powerful, and it can become a simple event collector to transmit the data collected by the multimeter to a computer. By using computers, detailed analysis can be conducted on every stable and unstable event. You can not only view the minimum and maximum values during each stable and unstable cycle, but also the start and end times of each cycle. Additionally, record the average value for each cycle. At the same time, it can dynamically detect the trend of voltage or current changes.
