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Multimeter DIY test leads gauge

markcopple

Mar 18, 2022
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Greetings! I am completely new to electronics so forgive me if this is a dumb question:

I am trying to fix an electrical problem in my car and I need longer test leads for my multimeter. I can see that it will be far cheaper to make my own test leads. What type/gauge wire should i use? I have Klein multimeter I purchased from home depot.

Stepping back from the question, I was shocked that you can get leads in a variety of gauges. I would think the gauge / material used would affect the results of some multimeter functions. Could someone explain? Thanks!
 

kellys_eye

Jun 25, 2010
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The gauge would be most affected when measuring current but since this requires you to break into the wire carrying the current you'd be 'right beside it' anyway so a set of longer leads wouldn't be necessary. As for voltage, this will be affected but only over distances much greater than you might be experiencing - you're not measuring the car from your bedroom are you? :p

In the case of resistance all you do is short the leads to discover the 'built-in' resistance and subtract that from any readings you take.

Use some cable of the same gauge as the existing meter wiring. The 'errors' will be negligible.
 

Harald Kapp

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Nov 17, 2011
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The gauge comes mainly into play when measuring currents: the higher the current, the thicker the wire.
I found a set of safety test cables rated 10 A with a wire cross section of 0.82 mm². That should give you an indication. For longer leads use probably 1 mm² to reduce losses when measuring currents.
When measuring voltages the cross section is (almost) irrelevant as the current is very, very low.
Use wire with an insulation rated to the specs of your multimeter (CAT IV 600 V/CAT III 1000 V).. Silicon insulation is flexible and temperature resistant which may come in handy when working on a hot motor.
 

ivak245

Jun 11, 2021
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If you are just doing continuity or voltage checks on your car, you could use a piece of flexible mains wire (like an extension cord ), and strip out the separate wires, solder some alligator clips on there, and you're away.
 
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