Multimeter‑Based Methods for Electrical Fault Testing and Detection
Many test instruments can simplify the diagnosis of intermittent faults.
These instruments include sophisticated signal analyzers and digital oscilloscopes, as well as easy‑to‑use handheld multimeters. Beyond basic measurement functions (AC voltage, DC voltage and resistance measurement), digital multimeters are equipped with measurement‑recording functions. Combined with standard forms, multimeters can capture fault parameters of intermittent faults.
In the past, mechanical paper‑chart recorders were used to continuously record voltage or current. During operation, voltage was applied to the input terminals or current sensors were clamped onto wires. The recorder printed voltage‑or‑current variations on paper tape, and the maximum recording duration depended on the remaining paper supply.
Ⅰ. Recording Intermittent‑Fault Data with a Multimeter
Activate the minimum / maximum / average recording mode of the multimeter, and select the corresponding function (AC voltage, DC voltage, resistance, AC current, DC current or frequency) according to the measurement item. Ensure the test circuit is properly connected before enabling the min/max/average function; otherwise the minimum reading will always show the ambient value obtained before test‑lead connection.
This will affect data analysis after the recording cycle ends. When the min/max/average recording mode is activated, the multimeter display shows the maximum reading and emits a beep whenever a new maximum or minimum value is detected.
Advantages: Provided the digital multimeter stays undisturbed and poses no safety hazard to personnel, it may be left on‑site for measurement while users attend to other tasks. Saved readings can be reviewed at any time throughout the recording cycle, and the recording mode can be paused without erasing stored readings.
Ⅱ. Continuous Recording of Intermittent Faults with a Multimeter
Some multimeters integrate the min/max/average recording function with another feature called AutoHOLD, together with larger memory capacity, to implement the Event Logging function.
The AutoHOLD function detects when measurement signals become unstable and when they return to stable conditions. Using AutoHOLD to trigger the start and stop of min‑max recording enables the digital multimeter to detect faults other than those that merely produce minimum or maximum values.
If the multimeter is fitted with an infrared RS232 interface, the continuous‑recording capability is further enhanced. The multimeter acts as a simple event collector and transmits captured data to a computer.
A computer allows detailed analysis of every stable and unstable event. Not only can users view the minimum and maximum values within each stable‑unstable cycle, but also the start‑and‑end timestamps of each cycle. Average values for each cycle are logged as well. Dynamic trend graphs of voltage or current variations can also be generated.
