AC current measure on mulitmeter

[Matt Roos]

Hi, All. I'd like to use my cheap radio shack multimeter to measure the
current from a wall outlet and use this to compute the Watts being used.
I'm thinking of taking a 3-prong extension cord and cutting one of the
wires, soldering on banana plugs and using this with my multimeter to
measure the current. Before I do this... are there commercially available
AC/banana plug cables like this I can purchase somewhere? Seems like this
would be a common application and I don't want to go out and buy a current
transformer ammeter.

Thanks,
Matt

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[Frank Pickens]

Matt Roos wrote:

Hi, All. I'd like to use my cheap radio shack multimeter to measure the
current from a wall outlet and use this to compute the Watts being used.
I'm thinking of taking a 3-prong extension cord and cutting one of the
wires, soldering on banana plugs and using this with my multimeter to
measure the current. Before I do this... are there commercially available
AC/banana plug cables like this I can purchase somewhere? Seems like this
would be a common application and I don't want to go out and buy a current
transformer ammeter.

Thanks,
Matt

--
Remove Xs from address to reply via e-mail.

Kiss your meter goodbye before plugging in.
fp

 

[Matt Roos]

The multimeter is rated for 10 Amps so for standard 110-120 V outlets it
should be okay for under ~1000 Watts, right? Many circuit breakers are
rated at 15 Amps so most loads from a single outlet shouldn't approach 10 A.

Matt

"Frank Pickens" <frankpickens@verizon.net> wrote in message
news:3FB70979.B0937298@verizon.net...

Matt Roos wrote:

Hi, All. I'd like to use my cheap radio shack multimeter to measure the
current from a wall outlet and use this to compute the Watts being used.
I'm thinking of taking a 3-prong extension cord and cutting one of the
wires, soldering on banana plugs and using this with my multimeter to
measure the current. Before I do this... are there commercially
available
AC/banana plug cables like this I can purchase somewhere? Seems like
this
would be a common application and I don't want to go out and buy a
current
transformer ammeter.

Thanks,
Matt

--
Remove Xs from address to reply via e-mail.

Kiss your meter goodbye before plugging in.
fp

 

[JeffM]

...measure the current from a wall outlet
and use this to compute the Watts
...3-prong extension cord
Matt Roos

These are not hard to make.
.. __ ____________
| \ | |
===------------------------------------| |
| | | |
| | 0.1 ohm 10 watt |AC voltmeter|
| | | |
===--------------+/\/\/+---------------| |
|__ / / \ |____________|
/ \
| |
| |
| | Make the meter lead connections
| | (called "Kelvin" or "sense" leads)
| | as close to the resistor as possible.
| | ____________
| |_______| |
| |AC voltmeter| 1V = 10 Amps
|__________________| |
|____________|
This will easily measure 20 amps.

BTW, your solution for measuring watts will not work
except on a pure resistive load (zero phase angle).
What you need is a wattmeter.