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  • Author Author: Matt
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4-Wire Resistance Measurements -- Workbench Wednesdays 19

 

 

Bench DMMs have an extra set of banana jacks called "sense." Known as a Kelvin or 4-wire measurement, these inputs accurately measure small resistances. Like, milliohms small. In this video, learn how to use a multimeter with 4-wire capability, prove 4-wire is more are accurate (in some cases), and a trick to get more accurate measurements with traditional 2-wire techniques.

 

Supplemental Material:

 

 

Bill of Material:

 

Product NameManufacturerQuantityBuy KitBuy Kit
MP730028 US Bench DMM, 5.5 DigitsMulticomp Pro1Buy NowBuy Now
Through Hole Resistor, 0.1 ohm, 3 W, ± 5%, Axial LeadedMulticomp Pro1Buy NowBuy Now
Through Hole Resistor, 1 ohm, 250 mW, ± 5%, Axial Leaded, 250 VMulticomp Pro1Buy NowBuy Now
Handheld DMM (72-7780)Tenma1Buy NowBuy Now
Test Lead Set, Banana Plug, Test Clip, Black, Red, 914 mmTenma1Buy NowBuy Now

 

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  • Very good post.

     

    I had not really looked into very low resistance values, though I knew they were important from a hot wire wind speed instrument I used about 45 years ago.

    I had never been shown the four wire method before, but it makes perfect sense.

     

    Thanks for bringing my knowledge up a little.

    DAB

Comment

  • Very good post.

     

    I had not really looked into very low resistance values, though I knew they were important from a hot wire wind speed instrument I used about 45 years ago.

    I had never been shown the four wire method before, but it makes perfect sense.

     

    Thanks for bringing my knowledge up a little.

    DAB

Children
  • in reply to DAB

    So, true story. When I started teaching "Measurement Basics" classes at my hackerspace, we had a bench DMM with 4-wire capability. I had never made a 4-wire measurement before, but I vaguely remember hearing about them in school (at that time, 10 years before.)

     

    Someone asked, "Hey, what is that for?" I said, "you know, I don't know. Maybe something to do with an h-bridge?"

     

    That day, I learned two things:

    1. The proper reason for 4-wire measurements, because, I looked it up later that night; and

    2. Be very careful what I say, when I'm not certain. The person wrote "h-bridge" down in their notes.

     

    That said, I was genuinely excited to make use of the capability for my upcoming DMM project.

    (stay tuned.)