Credit Card Sized DC Reference!
Being able to verify or calibrate multimeters is something that used to be available only to large labs that could afford to send their equipment off to a metrology lab. But in recent years, amateur voltage standards have become more and more accessible. This small, credit-card-sized voltage standard is good for up to 4.5-digit multimeters.
It’s very portable and can run using battery power. The batteries are charged via USB-C. Four different voltages are selectable: 2.5, 5, 7.5 and 10V. The unit is designed around the venerable Analog Devices AD584, which offers 15ppm temperature stability from 0 to 70C. This design uses the AD584T, which has a base accuracy of +/-15mV in the 2.5V range. Pretty good for testing your average handheld multimeter!
If you’ve wanted to see how accurate your voltage measuring equipment is, this is a great way to do spot checks. If you have a calibrated multimeter that can characterize the reference in this device, you could even use this device to calibrate 4.5-digit multimeters with very high accuracy! The datasheet for the AD584 goes into quite a bit of detail on how the device works and how to get the best performance out of it — definitely worth reading if you pick up one of these!