4 Wire Resistance Measurement

[Homer J Simpson]

Courtesy of; https://www.youtube.com/user/w2aew/videos on YouTube

[uncle_bob]

Hi

One wonders why outfits like Fluke write manuals and spec sheets. It's very apparent that people don't read them One would *think* that the manual would get read when your shiny new $1,500 DVM came out of the box. There's sure not much wear on that unit.

Bob

[edpalmer42]

Hi Bob,

I'm not sure what you're getting at.  Are you saying that the video is useful because people don't read the manual or are you saying that there's something wrong in the video? 

Ed

[uncle_bob]

Hi Bob,

I'm not sure what you're getting at.  Are you saying that the video is useful because people don't read the manual or are you saying that there's something wrong in the video? 

Ed

Hi

Fact checking the video against the manual and the spec sheet would come up with a long list of discrepancies.....

Bob

[Homer J Simpson]

What are the discrepancies ?

Is that meter specific or in the process / procedure?

[uncle_bob]

Hi

Ok, you are trying to demonstrate 4 wire measurement with a specific meter. That meter does certain things (puts 5 ma on the DUT) under certain conditions (R < 10 ohms). Rather that go through all the math with the numbers the meter does not use, ... use the ones it does use. It puts more current through a low R for a reason. When you do the "4 wire load part" ... the error is even closer to zero if you let the meter switch to it's 10 G ohm input mode. I wonder what Fluke actually does . The much bigger error is thermocouple errors (which he then demonstrates but does not explain).

The meter is *not* optimized for low resistance measurement. The lowest range is 10 ohms. Doing the demo with a mili ohm piece of wire is running it in a mode that it actually does poorly at. The demo of moving the "source" leads should show zero impact on the reading. It shows the reading bouncing all over the place. Yes, it's doing a massively good job to operate outside it's design range. The take away is that 4 wire doesn't work very well.

Yes I could go on ...

Bob