Louis at Scullcom Hobby Electronics has a new video updating the milliohm meter, and features the board I produced in this post.
NEW Link to updated video on YouTube
NEW Version 1.5 board available at OSH Park requires additional 0.01 uF ceramic capacitor, 2 pin header, and 250 mA PTC fuse.
NEW Updated project post with Milliohm Meter version 1.5 board.
It uses a 4 wire kelvin measurement system that supplies a precise 100 mA current to the device under test using one pair of leads, and then measures the voltage drop across the device under test using a second pair of leads.
As designed it can be used to measure low resistances of under 2 ohms (Ω). Some of the design changes I made to fit my needs were:
- Change the number of resistors needed in the current source circuit
- Use higher precision resistors with a low temperature coefficient
- Add separation and shielding between input, output, and supply circuits
- Use lower ESR and higher value capacitors for the MAX680 power supply
- Add additional decoupling capacitors on the INA106, and MAX680 IC’s
- Change the voltage regulator from a TO220 package to a SOT-223 package