I have had that experience too. You have to zero it, and also make sure
the wire you're measuring is going through the center of the loop and is
perpendicular to the loop.
bp
<part15sbs{at}gmail{dot}com>
On 1/25/2018 8:57 AM, ch...@wbmfg.com wrote:
Gotta make sure to zero those DC clamp on units before you use them.
Seems like every time I use one it takes me a bit of time to get it to
measure correctly.
*From:* George Skorup
*Sent:* Thursday, January 25, 2018 9:45 AM
*To:* af@afmug.com
*Subject:* Re: [AFMUG] Watts and VA on DC vs AC
Yeah. I guessed about 33 amps based on 13 volts. Could rise quite a
bit as the battery drains, and I'd expect the inverter efficiency to
drop as the battery voltage decreases.
I like having my handy Craftsman AC/DC clamp-on ammeter to verify my
poor attempts at math.
On 1/25/2018 10:12 AM, ch...@wbmfg.com wrote:
Your inverter is probably 90% efficient if you are lucky.
355 watts / .9 = perhaps 433 watts input
433/12 =37 amps input at 12 volts
So, yeah, your guess between 30 and 60 amps is pretty accurate.
You can also insert 1 foot of #10 wire in series with the 12 volt line.
Measure the voltage from one end of the wire to the other.
Millivolts = amps.
You should have about 37 milliamps volt drop across that wire.
*From:* Adam Moffett
*Sent:* Thursday, January 25, 2018 8:49 AM
*To:* af@afmug.com
*Subject:* [AFMUG] Watts and VA on DC vs AC
I wanted to rig up a load test for some batteries.
I don't have a substantial 12V DC load, so I set up a 1000W inverter,
a short extension cord, a Kill-a-Watt meter, and a heat gun.
With the heat gun on low, The kill-a-watt reads 110v, 606 VA, and 355W.
The question is how much load is this putting on the battery?
Somewhere between 30 and 60amp I guess, and either way my multimeter
can't measure more than 10A DC current, so I can't measure it directly.
My Googling on the topic has failed to enlighten me. My instinct is
to think that Watts is Watts, so I should probably use 355W in my
calculation of battery capacity, but I'm not sure.
