Building Frank's Milliohm Meter

RE: Building Frank's Milliohm Meter

johnbeetem — Thu, 03 Jan 2019 17:33:36 GMT

I once had access to a "Short Squeak", an uncalibrated milli-Ohmmeter in the form of a probe with a speaker. The lower the resistance, the higher the pitch. It was great for finding shorts, particularly in multi-layer PCBs and ground planes.

RE: Building Frank's Milliohm Meter

jc2048 — Thu, 03 Jan 2019 11:53:54 GMT

That's very neat and compact. The picture of it next to the Keithley box is lovely - perhaps you should have entered it in the Question of Scale competition!

How does it get on measuring the DCR of inductors? Is it stable?

I'm also wondering whether you'd get a sensible value for RDS(on) for a power MOSFET. Don't see why not, though the manufacturers do their tests at a much higher current (the MOSFET I've used in the load is tested at 27.5A!) and it does vary a bit with current. It would be a very easy experiment if you wanted to try it (perhaps bias the gate with a 9V battery so that there are no complications in that area).

RE: Building Frank's Milliohm Meter

jw0752 — Wed, 02 Jan 2019 21:19:10 GMT

Hi Shabaz and Frank,

You have made this a great international project and a good example of what I like about the forum.

John

RE: Building Frank's Milliohm Meter

genebren — Wed, 02 Jan 2019 15:40:16 GMT

Hi Shabaz,

This was a great write-up on your build and verification of Frank's work. In watching the video, I began to wonder if some of the variations in the readings between to the two instruments might be related to probe/clip placement differences during testing. As there is also some resistance in the crimped on connectors, you might want to make a series of marks to indicate where the clips should attach to the 'test resistor', so that you can eliminate this small amount of variance from the readings. Otherwise, it looked like a very clean build and a fair test of this cool little meter.

Well done!

Gene

RE: Building Frank's Milliohm Meter

fmilburn — Wed, 02 Jan 2019 05:47:53 GMT

Hi Shabaz,

That was a great review! Thanks so much. It was a lot of fun seeing it up next to the Keithley. Your build is fantastic. Most of the credit for the design reaching the current stage goes to the numerous people who gave comments and suggestions to me as it was not something I could have done alone. I am especially thankful to you for pointing me in a better direction on numerous occasions and cleaning up after some of my unforced errors. Version 2 should be coming in the next month or so....

Frank