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Old 03-25-2012, 05:44 PM   #1 (permalink)
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Clamp meters?

Are there any clamp meters out there that work well for measuring DC amp draw, or are they used primarily for AC amp draw? I've never used one and I'm not too familiar with them. Any recommendations?

Thanks
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Old 03-25-2012, 06:13 PM   #2 (permalink)
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Fluke 337 1000 amp, 336 (I think) is 600 amp

works great, what kind of amperages are you wanting to read (big like a starter/winch motor, or small like what your radio draws)?
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Old 03-26-2012, 04:01 AM   #3 (permalink)
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Originally Posted by xmptsunami View Post
Fluke 337 1000 amp, 336 (I think) is 600 amp

works great, what kind of amperages are you wanting to read (big like a starter/winch motor, or small like what your radio draws)?
Fuel pump and line lock for starters. I was hoping for something less than $100

Thanks
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Old 03-26-2012, 05:30 PM   #4 (permalink)
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I believe this Sears one does AC and DC current with the clamp.
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Old 03-26-2012, 06:09 PM   #5 (permalink)
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Originally Posted by 99tantj View Post
Fuel pump and line lock for starters. I was hoping for something less than $100

Thanks
For small amperages like that why don't you just wire in your meter in series. Most meters can handle up to ten amps, AC/DC and are much more accurate for small amps (probably).
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Old 03-26-2012, 06:13 PM   #6 (permalink)
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I believe this Sears one does AC and DC current with the clamp.
Wow, they crammed a lot of crap (features) on that little guy for only 62 bucks. That may be the ticket for automotive stuff, since you don't really need a ton of accuracy.

Still, for the small loads, running the current through the meter gives you a better scale (400 mA or 10 A) max as compared to 400, or 1000 amps.
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Old 03-26-2012, 06:34 PM   #7 (permalink)
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Mine is an off brand that i bought at car quest, it does up to 200amps ac and dc. It also checks Hrz values too, cost me around $160.
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Old 03-30-2012, 05:01 AM   #8 (permalink)
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Probably a stupid question, but I've never used my MM to check DC amp draw. I was messing around, checking my back up lights and it looks like they are drawing around 200 Ma. I've always heard a relay is needed for a light circuit. With these being LED's and having such a small draw, is there any reason to add a relay? I've got these lights and a few more in my LED lite dots.




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Old 03-30-2012, 09:55 AM   #9 (permalink)
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200MA is significantly less than the factory incandescent bulbs were drawing.

The concern with reverse lights is the backup switch in the trans. Hook up 55W fogs as backup lights and you toast the switch, which is why you need a relay.

no relay needed for LED's.
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Old 03-30-2012, 11:41 AM   #10 (permalink)
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200MA is significantly less than the factory incandescent bulbs were drawing.

The concern with reverse lights is the backup switch in the trans. Hook up 55W fogs as backup lights and you toast the switch, which is why you need a relay.

no relay needed for LED's.
Thanks, I forgot to mention I'm using an aftermarket shifter and have no trans back up switch. I'm just using a 20 amp carlingswitch. Lights are wired straight from fuse box
to switch to lights.

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Old 04-09-2012, 09:15 PM   #11 (permalink)
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Good luck reading amperage with dc and a clamp on. The clamp measures current via magnetic flux produced by ac voltage. If you measure anything it's just "noise" from the alternator and/or other electronics.

Sadly you have to put your meter in series with a dc circuit. Don't waste your cash on a clamp on unless you're an electrician and can actually use it,
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Old 04-10-2012, 08:21 AM   #12 (permalink)
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Originally Posted by chevy_man View Post
Good luck reading amperage with dc and a clamp on. The clamp measures current via magnetic flux produced by ac voltage. If you measure anything it's just "noise" from the alternator and/or other electronics.

Sadly you have to put your meter in series with a dc circuit. Don't waste your cash on a clamp on unless you're an electrician and can actually use it,
Yeah, nice try, but not really.

Internet quote:

A coil on the core is driven with a square wave AC voltage. The time for the square wave to saturate the core depends on the magnitude of the DC current in the conductor that is being measured.

Also FYI:

(This is as I remember being told or reading, and may not be 100% accurate):

Multimeters can't actually measure voltage or resistance directly, you have to measure either the amperage the voltage causes (through a known resistance), or apply a known voltage and measure the subsequent amperage.
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Old 04-10-2012, 09:30 AM   #13 (permalink)
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try this one

Extech 380941 200-Ampere AC/DC High Resolution Mini Clamp Meter

http://www.amazon.com/Extech-380941-...ref=pd_cp_hi_1
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Old 04-10-2012, 11:23 AM   #14 (permalink)
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I have a Fluke 336 Clamp meter, and take it on every trip. A/C, D/C Amps, Volts, Ohms, The clamp makes a handy way to hold the meter in a lot of places. It used to be calibrated by my former job and was accurate in DC Amps down to about 250 mA. At work I have their newer, smaller version for 4-20 mA loop signals, and that thing makes testing sensors, transducers, etc so much easier than always breaking the circuit to get in-line with it. Both these meters are pricey, and I was lucky to have the companies split cost or I never would have purchased them; Fluke is really nice equipment when using for calibration purposes.
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