Calibration, Good Old Calibration
Do you calibrate your digital meters? Most of us don’t have the gear to do a proper calibration, but [Mike Wyatt] shares his simple way to calibrate his DMMs using a precision resistor coupled with a thermistor. The idea is to use a standard dual banana plug along with a 3D-printed housing to hold the simple electronics.
The calibration element is a precision resistor. But the assembly includes a 1% thermistor. In addition to the banana plugs, there are test points to access the resistor and another pair for the thermistor.
In use, you plug the device into the unit you want to test. Then you clip a different temperature sensor to the integrated thermistor. Because the thermistor is in close proximity to the meter’s input, it can tell the difference between the ambient temperature and the meter. [Mike] says the bench meters get warmer than hand-held units.
This is, of course, not a perfect setup if you are a real metrology stickler. But it can be helpful. [Mike] suggests the precision resistor be over 100 ohms since anything less really isn’t a candidate for a precision measurement with two wires. Debating over calibration? We do that, too.
hackaday.com/2025/08/14/calibr…
