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Min/max, intermittents, and datalogging

By Robert Wavershak

August 2005

I had a power circuit shutting down every 2 or 3 days on a printing press. With an older Fluke 83 multimeter with Min/Max capability, I was able to determine that a small transformer was opening momentarily and causing the entire press to shut down. Intermittents are the worst thing. With some patience and Fluke test equipment, I was able to pinpoint the problem in a day and a half of recording voltages.

The meter's recording mode "Min/Max" is an excellent method of determining fluctuations in any circuit. This enables you to baby-sit a circuit to see exactly what's going on throughout the day or days. Simple to use. Attach probes to circuit first, so as to not record zero, press Min/Max and you're recording. When you want to retrieve what the meter has held in memory, press the hold button. Now, you can scroll with the Min/Max button thru average, max and min. Be careful not to hold down the Min/Max button longer then 1 second, as it will exit the Min/Max operation and erase memory. With any tool of this caliber, the manual is worth reading. Fluke makes the instructions easy to understand. It only takes a few minutes of reading to unleash these powerful diagnostics.