Right, I consider myself very competent in things Linux and somewhat competent with scripting. I've cobbled together some power monitoring using a RPi, Currentcost monitor, some Perl code and RRD files.
But I want to go a step (or in fact, a number of steps) further, especially as I'm getting a Solar PV system installed next week. With the Solar PV system I lose the ability to see how much electricity I'm actually using. I have negotiated with the installer that they will put an unofficial export meter on my installation. Both the export meter and the generation meter will be Elster Elster A100C electricity meters.
Although the CT clamps would enable me to monitor what I want, reading the meters using IrDA seems to me to be the "cleaner" (and safer?) option?
There is mention of a kit for reading from the Elster meter using IrDA, but I'm guessing the pulse input on the EmonTX would be used, and there is only one of those inputs?
So using two inputs is not possible using the EmonTX? Where reading using IrDA is discussed it is mentioned as something that can complement the CT clamps, why can't it be used as the main input?
Is the code for the Elster IrDA option even usable as is? It is mentioned that it is lacking transmitter code?
It is not clear to me how much, if any, programming is required to make any of this work, the "getting started" guide talk about "Upload[ing] the configuration specific firmware", is this more or less plug and play or does one need to perform any adaption of the code?
Re: I'm unsure what modules to use?
The emonTx has one socket which is ready wired for monitoring a photo-transistor. This is connected directly to one of the Atmega's interrupt lines, of which there are two. You could presumably use the second such pin in a similar manner for your other meter, and just replicate the supporting code.
Optical pulses from a utility meter can also be recorded using a passive LED. The circuit for this is very simple and can be found at the top of most releases of my Mk2 PV Router code. The firmware for this feature uses polling rather than interrupts, and there's no limit on how many meters you could monitor simultaneously - apart from the number of pins on the processor.