On 27 Mar 2005 08:06:28 -0800, jim rozen
wrote:

In article , wmbjk says...

A clamp meter is great for some larger loads, but useless for the
small ones. First accept this fact - one weeks *idle* consumption of a
TIVO, Replay etc. is equivalent to about 2 hours of the usual home
welding. Which ought to make it plain how the little things add up.
Now think about this - it's easy to read a 1 Amp variation when
wiggling an Amp clamp. So what's the point of using that on 1/4 Amp
loads? Then there's the time factor... how do you measure say, a
dishwasher with an Amprobe? You'd have to hover over the thing with a
stopwatch taking notes as it cycles through pumping, heating etc. Even
on a fridge, are you going to take a sloppy reading with a clamp
meter, and then clock the run time over 24 hours?

You can measure 1/4 amp loads with an amp-clamp actually.
The input is a transformer. Just make the pigtail long enough
to make 10 turns through the clamp part. Now the 1/4 amp load
reads as 2.5 amps.

That's probably the easiest way on the really small loads. We have a
Wattsup, and it doesn't register below about 3 Watts IIRC. But an
ammeter of any kind is still a bad choice on variable loads like a
clothes washer or a dishwasher, or for thermostat controlled loads
like a coffee maker or refrigerator. And even on the fixed loads, he'd
need to keep a log of hours. Use logs invite the common problem of
people seriously underestimating their hours of use. And he says he's
not home a lot, which means he'd need to take the word of others on
their habits. Considering that diddling, logging, and estimating can
all be eliminated with a $30 gadget....

The amp-clamp isn't a magic bullet. But the idea is to get some
idea of what stuff draws, where the current is going. And make
sure this squares with the watt-hour meter.

He can eliminate any possibility that the main meter is a problem by
running a known load and checking the reading. He's claiming modest
use in the face of $300 bills though, so if the meter were the
problem, it would have to be out by a factor of about 4.

He already has
both these instruments.

Sure, but given his comments so far, my take is that it's best to
recommend the easiest solution. Plus, there might be others reading
who'd like to lower their costs, and getting some of them to audit
their own use is more likely if the process is as painless as
possible. Here's another link to the Kill a Watt, $28 delivered
http://cgi.ebay.com/ws/eBayISAPI.dll...59390 66&rd=1
They've been on sale at times at Radio Shack.

Wayne