Kill A Watt P4400 on sale
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From: Jeff Liebermann on 5 Sep 2009 16:50 On Sat, 05 Sep 2009 13:18:10 -0700, David Nebenzahl <nobody(a)but.us.chickens> wrote: >On 9/5/2009 12:37 PM Jeff Liebermann spake thus: > >> On Sat, 05 Sep 2009 12:09:18 -0700, David Nebenzahl >> <nobody(a)but.us.chickens> wrote: >> >>> So how does this thing work? >>> >>> It looks like the power just passes straight through from plug to >>> socket over there on the left. Is there a current transformer in >>> there somewhere? >> >> I haven't ripped it apart and traced out a schematic (yet). As near >> as I can guess(tm), the big half loop near the power jack is a low >> value series resistor. >Ah, so. So the loop must be connected on one side to the incoming hot >line, and on the other side to the outgoing hot line. Then the unit >measures the voltage across the loop (resistor) proportional to current. >Right? Exactly. It's quite simple. There's usually a patent on something like this. Digging....bingo: "Electric adapter with display unit" <http://www.google.com/patents?id=G3MDAAAAEBAJ&dq=6095850> Nice explanation with a blockish diagram. My guess(tm) was wrong about half the instrumentation amp. It's even cruder than I thought. Some additional drivel on patent litigation: <http://greenpatentblog.com/2008/12/24/smartlabs-enjoined-parties-smart-management-focuses-issues-in-energy-meter-litigation/> I'm not sure of the final judgement in the case, but the infringing UPM Marketing device is probably the one I have on order and are being sold again by Smarthome: <http://www.smarthome.com/_/Cable_Structured_Wiring/Tools/UPM_Marketing/_/v/1P9/1wN/nav.aspx> -- Jeff Liebermann jeffl(a)cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
From: Dave Plowman (News) on 5 Sep 2009 18:12 In article <h7ue92$cdu$1(a)news.eternal-september.org>, William Sommerwerck <grizzledgeezer(a)comcast.net> wrote: > >> When I get around to it, I'm going to put it on my fridge for a few > >> days. I want to see exactly how many kWh it draws over a week or so. > >> You can't do that with a clip-on, because refrigerators run > intermittently. > > That's true - but what action will you take? You can hardly switch it > > off to save energy. Unlike heating and aircon. If it's old a new one > > will almost certainly be more efficient. But may cost more than it > > saves. > Correct. But I feel my electric bill is too high, Know what you mean. ;-) > and I need some evidence to argue with the utility. No method of getting them to check the meter accurately - IIRC in the UK they fit a second one to check the first. > I intend to measure everything in my condo. In my case I hadn't really noticed how much lighting load I had - and leaving lights on - until the price doubled. My house and water heating are gas. -- *Why isn't there mouse-flavoured cat food? Dave Plowman dave(a)davenoise.co.uk London SW To e-mail, change noise into sound.
From: William Sommerwerck on 5 Sep 2009 18:28 > Also, watch out for refrigerators that have self-defrosters. > Some are on demand, while others are on a timer. The > defroster sucks LOTS of power and will be a big part of > the electric bill. I intend to measure the energy over a week or so. That should average out things.
From: David Nebenzahl on 5 Sep 2009 18:37 On 9/4/2009 5:51 AM William Sommerwerck spake thus: > www.supermediastore.com has the "Kill A Watt" power/energy meter on sale for > less than $19, shipping included. Not quite. Singly they're $21.99. $19.99 ea. for 3 or more. http://www.supermediastore.com/kilwateldet1.html -- Found--the gene that causes belief in genetic determinism
From: William Sommerwerck on 5 Sep 2009 19:56
>> www.supermediastore.com has the "Kill A Watt" power/energy >> meter on sale for less than $19, shipping included. > Not quite. Singly they're $21.99. $19.99 ea. for 3 or more. > http://www.supermediastore.com/kilwateldet1.html In an earlier post, I indicated that you need a code... 94EL15P |