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Measuring amps with clamp meter

Old 03-01-2007, 09:34 PM
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cwharper
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Default Measuring amps with clamp meter

Is there anything wrong with using a clamp meter to measure dc amperage draw of brushless motors in the context of electric rc planes? I have a Fluke 179 multimeter and have been looking for an excuse to buy the i410 AC/DC current clamp meter.
Old 03-01-2007, 10:57 PM
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Bumstead
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Default RE: Measuring amps with clamp meter

If I am not mistaken, the Fluke will measure AC amps via the clamp as a coil.
Not easily adapted to measuring DC current above 10 amps without a suitable shunt.
Your better off springing for a Watt-Meter which will not only give you amps, but
peak watts, total mA draw etc. Makes thing a whole lot easier propping your
motor system properly.
Old 03-02-2007, 04:33 AM
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rm
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Default RE: Measuring amps with clamp meter

nope, if you just want to get a quick amp read, it's the easiest way to do it.
Old 03-02-2007, 10:08 AM
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infish
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Default RE: Measuring amps with clamp meter

I'm lookimg for a meter also, I'm new to elec. I did read some place that you should use some type of plug to measure your amps. watts ect..
I guess it's so that you don't short out your batt. the tabs are so small & close together. If anyone knows a web site please post. any info. or tips on elec. stuff I'm all ears.
thanks
-Tony ( infish )
Old 03-02-2007, 03:23 PM
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Ben D Wing
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Default RE: Measuring amps with clamp meter

I have the Graupner clamp meter and I would say it's the best gadget I've bought in years. Highly recommended![sm=thumbs_up.gif]
Old 03-04-2007, 11:04 AM
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Ron Kay
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Default RE: Measuring amps with clamp meter

Easy and Inexpensive DVM conversion to Read HIGHER AMP's

Next time you need to measure Amps try using your DVM (Digital Volt Meter). Very easy, set your meter on the lowest mV scale you have and put a shunt resistor across the leads. Done properly this can expand you DMV mV scale to read any amperage you need.

Briefly here's what goes on..

Assuming you have a DVM that has say has a 100 mV scale and you want to measure 100 A (DC) consider the following: In essence you would like to have a full scale reading of 100 mV (.1 Volts) while measuring 100 A ... so... Ohms law tells us that R (resistance in ohms) = E (volts) / I (current in amps) ... so... R=.1/100 = .001 ohm resistor. This tells us that if we put a .001 ohm resistor in PARALLEL with our meter leads we've transform our mV scale into a 100 A scale. Note, you may need to do some experimentation to get the meter calibrated but that's reasonable easy.

Same math applies if you have a DVM that has a 200 mV scale and you only need to measure say 50 A. The shunt resistor you will need in this case is ... R = .2/50 = .004 ohms.

The actual shunt resistor is nothing more then a short length of #12 or #14 house wire. In this example the shunt is approximately 1.8" of # 14 wire... Very easy to do and VERY, VERY easy on the pocketbook.

Good luck

Ron

PS: I failed to mention this setup needs to be in series with you battery ...
Old 09-19-2022, 12:01 AM
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I bought a Prasek PR-54 recently and watched a video tutorial. The volts seem spot on, which you measure with the diodes. I tested a 9V battery, the wall outlet, and my solar MC4 strings. The first two measurements were spot on. The last one, measuring VOC on a partly cloudy day, seemed also within reason.

Amps are another story. You have to use the jaws to measure amps. It can supposedly measure ranges of 40A or 400A, but can only measure one wire at a time, so, if you set the unit to AC amps, and measure a cable that holds both Line and Neutral wire, the thing won't even give a reading.

I set it to DC 40A and attached it around the 8 wires heading into my solar string box:

4 Groups, each with a negative and positive.
My array: 4s4p

The first three groups all measured somewhere in the ballpark of 2-3 amps on both their positive and negative cable. Those panels have a Vmp of 41.7V and an Imp of 9.6A.

The fourth group has another brand of the panel with mostly the same specs: 41.6Vmp and 9.86Imp.
The positive wire measured about 3 Amps, but the negative wire measured about 6 Amps.

This was pretty consistent, as I measured everything three times over the course of about ten minutes, and the outside light wasn't fluctuating very much during that time frame.
One thing I noticed, was that even when holding the multimeter far away from any wires, how to measure amps with a clamp meter it still gave off a reading of around 1 amp. I can understand the thing being inaccurate, but to consistently show a reading of around 3amps on a positive wire, and consistently show a reading of twice that for the same group's negative wire...

Old 09-23-2022, 12:01 AM
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Joseph Frost
 
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I have been using clamp meter to measure current draw in my high voltage 8-12S powered models for years, while ago bought 2nd. one just to confirm the figures.
Lot easier than using Eflite meter that I have to hook up inline, using special jumpers I use for different type on lover voltage models, 2-6S, but showing also Voltage, Wattage, Amps and under various load figures.

Easy current check with clamp type.



Lower Voltage 6S check by Eflite inline meter of twin 90mm Ruski tank.

Thorough check of all parras before flying action is a must!

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