I watched EEVblog’s video about debugging a short circuit with precise multimeter. He determined the direction of shorted place by comparing resistances in different places. I wanted to debug like that too and also measure resistances of wires and connectors, but all cheap multimeters measure only down to 0.1Ω. To get 10mΩ I have to buy 400€ multimeter. So I searched and found an article describing cheap and dirty way to measure low resistances. You need a known voltage source and known resistors and then you can form a voltage divider and measure the resistance. Awesome! But the form factor and all the math behind it sucks, as a plug and play device it would be perfect. I though about making it its own box, but was almost impossible to find cheap probe connectors for panel or PCB. So it will be a one PCB product.
First, the concept.
- It should measure resistances from 1Ω to 0.1mΩ
- General purpose – can be plugged in any multimeter.
- Output should be in mV, because most multimeters have mV display.
- No math, so 1mΩ is translated to 1mV and user doesn’t have to calculate anything.
- Precise enough – 1% is nice number, but it’s not very important, as usually we need the resolution, not the absolute precision.
Half Ohm – milliohm multimeter adapter - [Link]