There’s a few “built in” voltage references (in tables.txt version 0.0.8):
They seem pretty different:
{“model”:”DCSS AC910(Aus)”,”mfg”:”Radio Parts”,”cal”:20.72,”p50″:[2.17]},
{“model”:”Powertech MP-3027(Aus)”,”mfg”:”jaycar”,”cal”:23.18,”p50″:[0.92]},
Note the phase shift (2.17, 0.92) and calibration is different.
I’m using different ones:
- PowerTran 12V AC 0.5A M9265A (Altronics import)
- PowerTran 9V AC 1.33A M9233 (Altronics import)
The reference is labelled “9V” but “Most 12V transformers do not exceed 15V no-load, and work fine with IoTaWatt. At the low end, even a 6V signal is fine.”
If I test them using tables.txt edits (see below). I guess the phase shift and calibration but can tweak the calibration to match line voltage later.
{“model”:”PowerTrans12V(Aus)”,”type”:”U”,”cal”:20.00,”phase”:2.0}
{“model”:”PowerTrans12V(Aus)”,”type”:”U”,”cal”:16.00,”phase”:2.0}
Testing against some loads:
| JayCar Powertech | PowerTrans 9V | PowerTrans 12V | |
| Note | Existing in tables.txt, tested by Bob. | Guessed by Brett | Guessed by Brett |
| Heater | 1503W 1.0PF | 1500W 1.0PF | 1501W 1.0PF |
| Aircon Portable | ? | 1270W 0.98PF | 1280W 0.98PF |
| Vacuum | ? | 910W 0.87PF | 910W 0.88PF |
So it seems ok to use these. There is, I recall, a way to test the phase shift of a VT with the IotaWatt. Indeed: see here.