Reference Transformer Requirements

Hey team,

Looking at: https://stuff.iotawatt.com/product/9v-ac-reference-transformer-120v-us-plug/?v=3e8d115eb4b3

If we already have a 9V 120V US adapter with the same adapter/plug, can we just use what we have? Or is there something “special” about the recommended 9V transformer here for getting the reference voltage - that otherwise wouldn’t necessarily work for the IoTaWatt system with some random 9V adapter?

First, be sure what you have is an AC transformer, not a 9VDC supply. That said, any 9VAC transformer will work.

What’s special about the store model, and all of the transformers supported by IoTaWatt, is that the calibration and phase correction has been measured and incorporated into the configuration table.

Another factor is that I’m required to comply with regulations designed to reduce the phantom power used by the millions of devices that use wall transformers. That requires that the unit be efficiency level VI, which seems to only be achievable with a fairly hefty unit. There benefit in that the level VI requires very little phase-correction.

The standing offer is that I will calibrate, measure phase-correction and add to the tables any transformers (or CTs) that I am given two samples of. The current list is:

“VT”:[
{“model”:“generic120V”,“type”:“U”,“cal”:11.50,“phase”:2.0},
{“model”:“generic240V”,“type”:“U”,“cal”:20.00,“phase”:2.0},
{“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]},
{“model”:“Ideal 77DB-06-09(UK)”,“cal”:20.01,“p50”:[1.05]},
{“model”:“Ideal 77DE-06-09(EU)”,“cal”:19.12,“p50”:[1.48]},
{“model”:“Ideal 77DA-10-09-MI(USA)”,“cal”:11.06,“p60”:[0.10]},
{“model”:“TDC DA-10-09”,“cal”:11.20,“p60”:[1.14]},
{“model”:“TDC DA-10-09-E6”,“cal”:10.79,“p60”:[0.07]},
{“model”:“TDC DE-10-09(EU)”,“cal”:18.66,“p50”:[0.16]},
{“model”:“Jameco/100061”,“cal”:11.68,“p60”:[3.00]},
{“model”:“Jameco/102234”,“cal”:11.43,“p60”:[1.80]},
{“model”:“Jameco/2227444”,“cal”:11.51,“p60”:[0.58]},
{“model”:“Jameco/2270815”,“cal”:10.72,“p60”:[0.16]},
{“model”:“CUI 41A-9-1000”,“cal”:10.10,“p60”:[0.43]},
{“model”:“AX-27750-H”,“cal”:20.56,“p60”:[0.18]}
],

If you do use that transformer, you can configure as generic and there is a simple procedure to calibrate using a voltmeter or kill-a-watt.

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