Testing random meters for accuracy with DIY resistance tester.

I made a simple resistance tester for meters that tests them with 1, 10, 100, 1K, 10K, 100K and 1Mohm 1% resistors. I chose 0.5W resistors for the lower ranges and a high voltage resistor for the 1Mohm range to allow for checking insulation testers.

If you want to make a similar tester for electrical installation meters the two most useful resistor values are 1 ohm and 1 megohm. The 1M resistor will need to be rated for 1kV or more for insulation testers that can test at that voltage. It's a good way to check a meter is functioning correctly.

The only time I've seen electrical installation test meters go out of calibration is when they've been abused. Usually involving applying the probes to a live supply and then attempting to do a resistance test on it despite the warning light being lit. Modern meters try to be idiot proof by preventing the test being done, but ironically they are less reliable because of the more complicated circuitry.

The routine calibration thing appeared at the same time as the Part P protection racket was pushed for by organisations who make a LOT of money from it. It's part of the same detached paperwork industry that brought us the five-day electricians certificate. (The same reason meters now need to be idiot proof.)

It's reassuring to see that my old American-made Fluke from around the early 1990's is still reading accurately.

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