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### Topic: Measuring current above 10A (Read 8230 times)previous topic - next topic

#### westfw

#16
##### Jan 06, 2013, 12:59 am
Don't forget that at 40A, your "test leads" will need to start looking like the cables used to jump start automobiles.  Standard house wiring (14g solid wire) is only good for about 15A...

#### DirtBiker

#17
##### Jan 06, 2013, 03:16 am
If the conductors are not double insulated (like Romex) and within the walls of house, #14 wire is actually rated at closer to 30 amps.  For 40 amps over short runs you could theoretically get by with #12 wire, but for sufficient safety margin, I'd go with #10 at least.

#### westfw

#18
##### Jan 06, 2013, 03:29 am
Quote
If the conductors are not double insulated (like Romex) and within the walls of house, #14 wire is actually rated at closer to 30 amps.

Could be; I was looking at the Romex specs.
Um.  Are you actually allowed to use not-double-insulated wire in your house these days (I guess the answer depends on where you live...)

#### DirtBiker

#19
##### Jan 06, 2013, 03:41 am

Um.  Are you actually allowed to use not-double-insulated wire in your house these days (I guess the answer depends on where you live...)

I think only if it is in an approved conduit or cabinet (or wiring box).  I think it's the same up in Canada.  My brother in law is an electrician in Ontario.  According to him the US and Canada have basically the same rules.

#### zoomkat

#20
##### Jan 06, 2013, 03:59 am
What is the voltage driving the 40a? if it is low like 12v, then look to the automotive world for gizmos like below. Depending on the driving voltage, you should be able to make a shunt that would be optimized for the power that will be disipated and still with a decent measurable voltage drop across it. Also, what is the gizmo thru which the current is to flow (assuming you are not doing a dead short smoke test)?

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