A tool to measure current above 10 amps

Up until now I've never REALLY needed to measure anything above the 10 amps. I've had this same hand-held DMM forever. I know it's probably not as accurate as the test lab equipment I see people use, of course - for what I am doing and can afford, serves the purpose.

I'm starting to build large robots using lead car batteries. I would like to make my own circuitry to monitor the current consumption during use. Usually I hook up my multi-meter and test current consumption for less then 10 amps, and use the multi-meter as my tool to check against my current-consumption sensor circuitry. So above 10 amps, I can't really test my current-loggers if I don't have another tool to check make sure it actually works correctly.

Can someone tell me, what tool or gauge can I buy - next step up (economy / not expensive) from a handy multi-meter to get accurate current consumption - for, up to about 100 amps?

Make a shunt out of 14AWG wire.
Measure the voltage across the shunt, slide a wiper so at 1 amp you get 10 millivolts.
Solder the wiper in place.

Therefore 100mv is 10 amps.
Therefore 200mv is 20 amps.
You get the idea . . . . .
1 volt is 100 amps.

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<= 10AWG for 100A, or you have a fuse. 14AWG will dissipate nearly 100W/m at 100A.

At this kind of current level hall-effect sensors are a good idea as they aren’t affected by
changes of shunt-resistance due to self-heating.

Checkout the ACS756 family for instance

Hi, thanks for the responses. I'm not looking to build my own sensor or create a multi meter from scratch. I was looking to buy a meter, that was already built - for me to use, so that I can actually test the things that both MakT and LarryD are describing. I want a calibrated tool, for me to build current sensors - to check the sensor I build, against something that I know will give a reliable reading.

I think I need something like this:

eBay analog current meter 100 a

DocStein99:
Hi, thanks for the responses. I’m not looking to build my own sensor or create a multi meter from scratch. I was looking to buy a meter, that was already built - for me to use, so that I can actually test the things that both MakT and LarryD are describing. I want a calibrated tool, for me to build current sensors - to check the sensor I build, against something that I know will give a reliable reading.

I think I need something like this:

eBay analog current meter 100 a

Enlarge the picture and you will see it is designed to read 75 millivolts across a shunt.

Paul

Or for convenience any RC store or EBay or Amazon will sell you a wattmeter. Simultaneous measurement of voltage and current usually up to about 50V and 100A. Something like this one.

Steve

Slipstick: Ok that device looks like something I can use. It's cheap enough, I can use it for just about anything.

A clamp meter with DC function will work best. You can measure current without even connecting the wire in series and some good models can measure up to 400Amps

Here's one in action

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Clamp meters are great but make VERY sure it will measure DC current. Many of the cheaper multimeter style ones sold as "AC/DC meters" will measure DC voltages but only AC current.

Steve

slipstick:
Clamp meters are great but make VERY sure it will measure DC current. Many of the cheaper multimeter style ones sold as "AC/DC meters" will measure DC voltages but only AC current.

Yepp,

Also make sure to get decent one like pictured above if you want accurate measurement since -->

DocStein99:
I want a calibrated tool, for me to build current sensors - to check the sensor I build, against something that I know will give a reliable reading.

DocStein99:
It's cheap enough, I can use it for just about anything.

-One does not simply expect precision measurements from cheap instruments.

Noobian:
Yepp,

Also make sure to get decent one like pictured above if you want accurate measurement since -->
-One does not simply expect precision measurements from cheap instruments.

It sounds like a conflict. I want an accurate CHEAP tool. Lol.

Before I pick something out, I usually go to youTube, find a tear-down and see what's inside. I watch someone else probe it using THEIR expensive lab equipment. For me, I do not need to pay $200 extra for the FLUKE brand multi-meter, just because the banana jacks are strong and indestructible - with mostly all the same stuff on the inside and a 120ms difference between the "BEEP" time on a continuity test.

After I find an estate auction or yard sale where the people are selling Grandpa's expensive equipment, then I can probably afford to buy the nice bench equipment with the 4 decimal precision readouts.

Fluke's not the only kid on the block. lol. :stuck_out_tongue:

Also expensive instruments are more that just rock hard banana plugs and adamantium chassis and blast processing. There's also a factor called precision involved. Especially when you need a meter to calibrate your sensors.

In the end it all just boils down to how much you're willing to compromise. If you're ok with a +/- 5% accuracy then you can go with a 5$ clamp meter, Else if you want +/- 0.5% accuracy you have to choose a decent meter.

Personally I use Cheap clamp meters because my requirement doesn't need that kinda accuracy. I just use them to measure amperage of ordinary light bulbs so I don't care whether the amp reading given by my meter shows 0.16 amps or 0.17 amps because I use approximation and get my wattage result.

Since I presume you need it for a one time use only, I suggest you can borrow one from a nerdy friend of yours for a couple of days and then return it instead of waiting for someone's poor ole grandpa to... you know. :slight_smile: