STM32 Open Source Multimeter
This is wonderful!The tricky part of a multimeter is not the digital part (which is a knob in many multimeters) but the analog part: calibration, stability, noise.  (And, as martin points out, safety.)  The three-to-five-digit output here suggests an accuracy of ±0.05% or better, which is not easy to achieve, and it turns out at the end that the accuracy is about ±5%.  (Expensive multimeters can deliver 7 digits, and for real.)  In theory the STM32's ADC can deliver ±0.1% error easily, and its internal bandgap reference ±2% (accuracy, not reproducibility), so it ought to be possible to do better.  But I happily used analog multimeters with several percent error for many years.  In fact, I still do sometimes!If you like this multimeter, you'll probably like the M328 "DIY hobby Arduino voltmeter" or "AVR component tester", which you can buy prebuilt from a variety of places.  It does component identification — it's a full RLC meter, with automatically triggered transistor and diode test modes — but is unfortunately built around the AVR, limiting it quite a bit.  And it usually (always?) has pretty poor precision.Is there an alternative repository to Thingiverse yet?  They're run by notorious bad actor MakerBot, so depending on them to archive our manufacturing knowledge hardly seems prudent.