Over the years most of us have purchased a few multimeters, and perhaps some of the older ones are still hanging around like faithful friends. You might prefer one ahead of the others, perhaps because it is easier to use and you think that it is probably more accurate, but you wonder just how accurate it is…
Determining the accuracy of a DMM is not easy. Often manufacturers will totally ignore accuracy in their specifications, or if it is a high quality model, they might say something like ±0.02% ±3 digits ±4mV/°C — which does not help either.
This gadget will output a precise 2.500V with an accuracy of ±1 mV. It is great for checking any meter, it does not cost much, and it must be one of the simplest projects around.
MAX6325 Precision Voltage Reference - [Link]