Welcome to the Thursday Toolkit series, about tools for building Physical Computing projects.
The nice thing about this unit is that it’s fully self-contained (with a 9V battery on the back) and that it has all the bits and pieces on board to check a multimeter’s (DC) voltage, (DC) current, and resistance measurements.
It comes with a calibration report – the voltage has been trimmed to exactly 5V, but the rest will have slightly different values due to component and temperature tolerances. Also, it was calibrated at 70°F (21.1°C):
Here are my HP 34401A measurements, with only 15 minutes warm-up (it’s now about 23.5°C here at JeeLabs):
Very close – more than close enough to start checking the VC170 multimeter I described recently, for example:
Easily within spec. Note that a VC170 only has 400 µA + 400 mA ranges, and 1 mA only shows 2 decimal points.
Here’s a higher-spec VC940, which I find unconvincing – I use it rarely anyway, due to its slow refresh rate:
Here’s a very low end Extech MN15 – it performs worse than the VC170 and can only display values up to 1999:
And finally, as flash from the past, a cheap analog multimeter – this one is probably over 30 years old:
We’ve sure come a long way, from trying to guess the value while not mixing up all those scales!
This reaffirms my choice of using the VC170 for day-to-day use, with the high-end HP 34401A used for top accuracy and for long-running experiments (handheld multimeters always auto-shutdown much too quickly).
As you can see, the DMMCheck is an superb little tool to quickly do a sanity check of your multimeter(s). There’s now also a DMMCheck Plus with extra signals to check AC voltage + current, and even frequency + duty cycle.
If you take lots of measurements over the years, it’s well worth getting something like this to verify your DMM.
This all relates to a discipline called metrology (no, not “meteo”, but “metrics”) – i.e. the science of measurement.