Just a quick question on using the supplied 9V AC adapter for the EmonTX V3 on Australian voltages -
we are nominally 230V 50Hz, although in reality we run/allowed (in Victoria/Australia) 240V (216V - 264V), 50Hz (see here )
I am monitoring my grid voltage via my PV Inverter (Aurora) and it varies between 235-257
Would the standard 9V AC-AC adapter (with a simple UK-AUS plug adapter) work OK ?
thanks all
Re: 9V AC adapter for Australia
It will probably be OK. The maximum UK voltage is 230 V + 10%, so 253 V. The adapter is effectively unloaded, so should not overheat, but the core losses will be higher so the iron will give out more heat even though the copper will be quite cold; and the phase error will be markedly worse at the top end of the voltage range. If the adapter feels unhealthily hot in use, it's probably a good idea to seek an alternative that's suitable for the higher voltage.
Re: 9V AC adapter for Australia
The main reason I want to use the 9V AC source is for accuracy. Given a normal domestic resistive loads what would be the accuracy of CT clamps alone ? compared to the clamps and the voltage reference for my situation (where voltage is probably above 250 for around 5 hours/day
thanks
Re: 9V AC adapter for Australia
There's a Building Blocks article on accuracy that might help a bit. Obviously it's impossible to say what the error in power reading will be if the voltage varies from the nominal that you've told it without knowing the actual voltage! The total error in energy will tend to average over time, if the nominal voltage is set correctly the long-term error could be zero whilst the instantaneous power error and the short-term energy errors might both be significant.