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Old 01-17-2009, 05:13 PM   #1
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Measure Amps


Is there a way to measure amps with a Digital RMS multimeter without a clamp? I have a Ideal True RMS 361.

Jamie

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Old 01-17-2009, 05:16 PM   #2
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Measure Amps


you can usually get an add on clamp that plugs into the same lead terminals as the probes do.

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Old 01-17-2009, 05:18 PM   #3
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Quote:
Originally Posted by jamiedolan View Post
Is there a way to measure amps with a Digital RMS multimeter without a clamp? I have a Ideal True RMS 361.

Jamie
By measuring the mV across
a real shunt made of Constantan, or, possibly, Nichrome, or
across a few feet of copper wire. The temperature coefficient of resistance for copper is not too bad.

You can also use coat hanger wire as a 20A or 30A shunt but the resistance changes so much with heating that you need a lookup table to approx. the true value of current.

You can also make a shunt by paralleling many cheap power resistors from Hosfelt.com. That's how I made 0.1 and .01 ohm shunts. Sometimes you can get these resistors for a few cents each.

Having blown out my meter's 0.5A internal fuse (for the 200mA range) a few times, I'd definitely go with a shunt.

For elec. troubleshooting, it also doesn't hurt to have a 100 ohm, 100w resistor, or equiv. I got mine for free at a Hamfest.

Last edited by Yoyizit; 01-17-2009 at 05:29 PM.
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Old 01-17-2009, 05:35 PM   #4
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Measure Amps


Quote:
Originally Posted by Yoyizit View Post
By measuring the mV across
a real shunt made of Constantan, or, possibly, Nichrome, or
across a few feet of copper wire. The temperature coefficient of resistance for copper is not too bad.

You can also use coat hanger wire as a 20A or 30A shunt but the resistance changes so much with heating that you need a lookup table to approx. the true value of current.

You can also make a shunt by paralleling many cheap power resistors from Hosfelt.com. That's how I made 0.1 and .01 ohm shunts. Sometimes you can get these resistors for a few cents each.

Having blown out my meter's 0.5A internal fuse (for the 200mA range) a few times, I'd definitely go with a shunt.

For elec. troubleshooting, it also doesn't hurt to have a 100 ohm, 100w resistor, or equiv. I got mine for free at a Hamfest.

because we all know buying the right equipment is way to hard and safe....
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Old 01-17-2009, 05:47 PM   #5
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because we all know buying the right equipment is way to hard and safe....
Since I tried to blow the whistle on my Fed. Gov. employer, I have a lot of time on my hands and not too much money in my hands. . .

I can't see paying for some of this stuff if you can make it out of junk box parts and it works just as well, for household applications.

BTW, with all due respect, it's ". . .way too hard. . ."

Last edited by Yoyizit; 01-17-2009 at 05:49 PM.
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Old 01-17-2009, 05:49 PM   #6
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Originally Posted by Yoyizit View Post
Since I tried to blow the whistle on my Fed. Gov. employer, I have a lot of time on my hands and not too much money in my hands. . .

I can't see paying for some of this stuff if you can make it out of junk box parts and it works just as well.

With all due respect, it's ". . .way too hard. . ."

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Old 01-17-2009, 05:52 PM   #7
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Measure Amps


Quote:
Originally Posted by jamiedolan View Post
Is there a way to measure amps with a Digital RMS multimeter without a clamp? I have a Ideal True RMS 361.Jamie
You most likely can but with most meters, mine especially, it's 10 amps max, and your leads need to be in series with the load. I wouldn't aatempt to measure amperage with my meter unless I was ina process control environment and I'm just trying to test 4-20mA.

And if you forget to change the location back and go to test voltage, hopefully it's fuse protected. from personal experience of course.( I always have a box of fuses for my 787, CRS ya know)
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Old 01-17-2009, 06:11 PM   #8
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That's OK if your name is Christine. . .
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Old 01-17-2009, 06:38 PM   #9
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Ideal actually sells the 361 with a clamp on meter accessory. Together they come under the model number 61-363. That is a combo of the 61-361 meter and a 61-450 clamp. Capacity is 300 AAC. Not sure if the other smaller capacity accessories would work but I see no reason they wouldn't. Check with an Ideal dealer to be sure.

for some reason I am having trouble with Ideal's website and cannot look for the answer.
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Old 01-17-2009, 11:45 PM   #10
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Measure Amps


Quote:
Originally Posted by Yoyizit View Post
By measuring the mV across
a real shunt made of Constantan, or, possibly, Nichrome, or
across a few feet of copper wire. The temperature coefficient of resistance for copper is not too bad.

You can also use coat hanger wire as a 20A or 30A shunt but the resistance changes so much with heating that you need a lookup table to approx. the true value of current.

You can also make a shunt by paralleling many cheap power resistors from Hosfelt.com. That's how I made 0.1 and .01 ohm shunts. Sometimes you can get these resistors for a few cents each.

Having blown out my meter's 0.5A internal fuse (for the 200mA range) a few times, I'd definitely go with a shunt.

For elec. troubleshooting, it also doesn't hurt to have a 100 ohm, 100w resistor, or equiv. I got mine for free at a Hamfest.
Thanks for the suggestions. You always have a lot of neat ideas that I would love to try when I have a bit more time. :-)

I did find some of the clamps on the web as nap suggested, all of the ones I found for this meter were over $200, yikes. I'll just buy a RMS clamp meter for well less than that.

Thanks guys for the input.

Jamie
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Old 01-17-2009, 11:47 PM   #11
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Measure Amps


Quote:
Originally Posted by nap View Post
Ideal actually sells the 361 with a clamp on meter accessory. Together they come under the model number 61-363. That is a combo of the 61-361 meter and a 61-450 clamp. Capacity is 300 AAC. Not sure if the other smaller capacity accessories would work but I see no reason they wouldn't. Check with an Ideal dealer to be sure.

for some reason I am having trouble with Ideal's website and cannot look for the answer.
I must have been looking at a different model. I found the part number you suggested for $50 (http://www.tequipment.net/Ideal61-450.asp).

Thanks! Do you think I am better off getting this accessory for the meter I have or buying a separate RMS clamp meter.

Thanks
Jamie
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Old 01-17-2009, 11:53 PM   #12
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It depends on what your needs are. I prefer a clamp on meter but I use it frequently. The add on device is something you have to store somewhere when not used and using it means you have to plug it in (not a big deal but just one more thing). When I need to do an current check, I like having my my meter right there already.

It also makes a handy meter hook when checking other values.
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Old 01-17-2009, 11:58 PM   #13
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Measure Amps


Quote:
Originally Posted by nap View Post
It depends on what your needs are. I prefer a clamp on meter but I use it frequently. The add on device is something you have to store somewhere when not used and using it means you have to plug it in (not a big deal but just one more thing). When I need to do an current check, I like having my my meter right there already.

It also makes a handy meter hook when checking other values.
I've notice that. I have a cheap $15 harbor freight clamp meter, but I just don't trust that it is that accurate. But I wonder how much difference there would be between the harbor freight meter and a RMS meter.

Jamie
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Old 01-18-2009, 12:06 AM   #14
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Measure Amps


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Originally Posted by jamiedolan View Post
I've notice that. I have a cheap $15 harbor freight clamp meter, but I just don't trust that it is that accurate. But I wonder how much difference there would be between the harbor freight meter and a RMS meter.

Jamie
You can buy a Greenlee clamp on ammeter for around $60.

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