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August, 2017 update: The DMMCheck is no longer available. The company does make other calibration devices, though.
How accurate is your DMM? If you work for a decent-sized company they probably calibrate at least some of the test equipment every year. But many others never check calibration. Buy a meter off eBay and you have no idea if reads accurately.
I recently came across the Voltagestandard web site which offers a number of low-cost references and ordered one of their DMMCheck devices. The specs are amazing considering the price:
- 5.000 volt output reference, accurate to 0.01% +/- 500 µV
- 1.000 mA reference, accurate to 0.1% +/- 1 µA
- Three 0.1% resistors: 1K, 10K and 100k
The unit runs off an included 9 V battery.
It comes with a calibration certificate, and its accuracy is guaranteed for six months. For the first two years recals are free (user pays shipping) and after that it's $5. The vendor checks each unit against an 8.5 digit DMM that is recalibrated every year.
DMMCheck calibration certificate
The DMMCheck's 5 volt output
Obviously, this unit provides only a few fixed values and doesn't substitute sending your DMM to a cal lab, but at $35 (for 25 PPM resistors; add $4 for 10 PPM) it's a bargain for those who don't get regular meter calibrations.