From memory and experience the devices you listed at the end all work on current clamps. So as current clamps only work with resistive loads they are going to be inaccurate by design. The devices mainly discussed in this thread are DIN mounted and measure both current and voltage to output power.
Paul
yep, that's right ... looks like I got my threads mixed-up - thought it was this one that had mentioned the current clamp meters ... looking back, though, now, it seems there was just a passing reference to the Current Cost ... ie: maybe it was the earlier thread that took them more seriously !
I'm just setting up a trial between one meter I brought from the German company I wrote about on this forum (which will do a max current of 32A) and one from Stephen P Wales (which will do a max current 45A) all in series along with a CALMU calibrated kwh meter. All three also going into a QRI-002 to compare the pulses. As the din rail mounted units only output 20ms length pulse which is right on the limit that Karam says will work. Fingers crossed!Originally Posted by Gumby
I needed one at 45A for one of the showers. Comparing the two units, they look to be from the same source with moulding marks in exactly the same area, with only the ID on the side being different.
Will follow up in a couple of days.
(bit more than a couple of days!)
The results were as follows. Over a two day period, all lighting circuits were fed via the three meters. I have also got 15 days worth, but thought I would hit the two days first to see if it's worth going for the 15 days.
59 pulses from the Calmu meter = 0.59 kWh, the meter read 0.59 kWh. The meter setup was verified with a tungsten lamp at 40w and it did read 40w.
698 pulses from the 45amp meter = 0.698 kWh, the meter read 0.70 kWh. There was no setup to verify.
705 pulses from the 32amp meter = 0.705 kWh, the meter read 0.70 kWh. There was no setup to verify.
7 pulses diffrent. So only a 0.01% issue there. But the two din meters did read quite a bit higher.
I am going to put the Calmu meter on my incomer and will verify that against the rec. meter. But I will be changing CT's from a 20/5 to a 80/5 for this. I will be using the 20/5 with another Calmu meter and will compare against one of the din modules to work out the diffrence.
I am more interested in that the Calmu meter seemed to be spot on, both in pulses and the reading. The DIN meters are to be used in a more indicative role, so that I know roughly where the power is being used.
I have split off all the computers onto one big UPS now, and will feed them separately. So will have a house base-load and also a computers base-load. I think I am going to find this info scary.
Am ordering another 11 of the 32A meters later on today. Will be interesting later on to add them all up and check to see if they are still appear to be reading high. Will also now do a check against one of the ring main so will have some proper amounts of kWh to play with
Next task - water and gas meters.
Cheers
Richard
Interesting Richard - Aside from the actual accuracy of the measuring I would always have expected the pulse counts to read low if anything (if there were any pulse missed) . So it seems either the DIN units do measure high - or the Calmu low - although you have verified it against the load. I gather it's connected via CT's - and I assume has a voltage connection too ? I wonder if they vary and light loads introduce more error.Will be interesting later on to add them all up and check to see if they are still appear to be reading high. Will also now do a check against one of the ring main so will have some proper amounts of kWh to play with
Next task - water and gas meters.
Cheers
Richard
I have my gas and water metered and the pulse widths are no problem there. My water meter is quite sensitive but the gas less so. I tried to order a more pulses/m3 gas meter but the company said they were all the same, based on a standard. These meters, particularly the gas one, do click a bit as they count so worth ensuring they are out of earshot.
These sort of exercises do pay off as you become obsessed with consumption. My computers that were 24/7 are a major electrical culprit as the graphs clearly show. I've got a few ZigBee plugs that switch/monitor KWHr too on particular appliances.
At the moment I'm focussing on heat loss from my hot water tank. I have a circulating hot water system, along with a towel rail off a secondary coil in the cylinder and it's surprising how much extra heat loss this causes. I'm looking at timing or intelligently switching these two. With the circulating hot water however this causes a churn of cold water back into the cylinder.
K
Last edited by Kevin; 26th October 2009 at 01:25 PM.
v.interesting - thanks for posting ... not sure the test with a 40W bulb would be anything but a rough guide (unless I misunderstood), their rating must be nominal & of course dependent on voltage ... the house meter might be the most accurate, if some way of running them (or just the CALMU, if that's in-doubt) against it for at least a few hours, preferably days, could be devised ... mind you, 'would've thought the CALMU would be OK !
Last edited by chris_j_hunter; 26th October 2009 at 06:47 PM.
looks like Current Cost have some new units out :
http://www.currentcost.com/products.html
useful or ... ?
Chris
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