Hi All,
Just received my IoTaWatt last weekend and I’m extremely impressed so far.
The resolution of the data, amount of data presented and the built in graphs are all fantastic.
I have noticed that my incoming voltage seems to be approximately 4v too high.
I’m in the UK and everything else in the house suggests I’m running at a nominal 242v, yet the IoTaWatt seems to constantly be about 3-4v higher (245.7v).
I don’t have a properly calibrated meter to test against, but my 2 cheap RMS meters as well as a plugin monitor and a couple of my servers all seem consistent with the lower voltage.
I am using the IdealPower DE-06-09 wall-wart via a plug adapter to convert it to a UK 3-pin plug configured in IoTaWatt as “Ideal 77DE-06-09”.
As I believe they come pre-calibrated, I’m a bit wary of messing with it without getting confirmation first.
3-4V is about 1.6% high. Not too far off, but the TDC (Ideal) adapters are usually closer than that. A real RMS meter usually isn’t cheap, so I have to wonder.
If you have a more reliable standard, you can easily calibrate the IoTaWatt using this procedure.
Before doing that, you can try a couple of things to validate:
Matching the IoTaWatt kWh to your meter over several days should show an overstatement of kWh if the voltage is actually that high.
Don’t know if available for 230V systems, but I’ve found the Kill-a Watt to be pretty good for RMS voltage and they are very inexpensive.
In the UK, the declared voltage and tolerance for an electricity supply is 230 volts -6%, +10%. This gives an allowed voltage range of 216.2 volts to 253.0 volts.
I’m was aware there’s quite a variance in allowed voltages in the UK - I was more questioning that the IoTaWatt is reading slightly higher than anything else in the house.
Previously I was convinced that the electric meter was reading too high as the “instant/current” wattage reported always seems to be slightly higher than the IoTaWatt, however after leaving both devices alone for 24 hours the CAD is reporting 13.01kWh used and the IoTaWatt showing me 13.0kWh, so the meter still seems to be reading higher, even if the voltage is slightly too high on the IoTaWatt.
I have to be honest, I have very little trust in the electric meter - one of the main reasons I bought the IoTaWatt is because it told me last week I was using 2750kW (at £380/hour), and even previous to this it’s seemingly slightly higher than I’d expect.
I would consider that to be exactly the same, less than 0.1% difference.
If you believe the other voltage references to be in concurrence and more accurate, you can easily use the calibration procedure above to makeIoTaWatt agree.
Meters are usually within 0.5% or better, but could be. Not familiar with a meter that reads kWh to two decimal places and shows real-time kW. I would expect that to be a fairly new electronic meter.
I think I’ll wait until I can borrow a calibrated MFT to get known-good voltage readings and then calibrate the IoTaWatt to match that.
In the UK, we had a massive (if somewhat controversial) push to get everyone onto “Smart Meters”.
My current meter is a SMETS-2 smart meter which comes with a little wireless screen (powered by Zigbee, though they refuse to let you connect your own Zigbee device to it’s network to monitor it) which shows current (updated every 10 seconds) and historical usage from the meter as well as the cost.
It’s a nice idea, but considering it told me last week I was pulling 2.7 MEGAwatts of power (£380/hour), it’s certainly not without issue. Interesting phone call to the supplier, where they decided that the meter was sending them data so it must be working properly. (“but it’s over 11,500amps, if that was correct my house and everything between my house and the power station would be on fire!”).
