STM32 Open Source Multimeter
This is wonderful!<p>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!<p>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.<p>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.