Is there any plan to add DC current and DC tension sensors to the system ?
I would be interested to monitor a solar photovoltaic system without an inverter. I would use it under 12V DC.
It would also be interested to monitor DC system like autonomous house ou boat.
In the documentation, I saw anything but DC shunt.
I begin to test an add-on with an ADC and some current sensors that I could plug on the emonPi. I need to modify the atmega code but it seems to be not too hard.
If you search the old forums, you will find that there are designs that take d.c. inputs. The problem is one of safety and isolation: it is easy to measure an alternating voltage and current using voltage and current transformers respectively, and these provide the isolation from the mains voltage that is necessary for your safety.
There is no cheap and simple equivalent to the transformer that you can use on a d.c. system, and unless your d.c. system is grounded and shares a common ground with your measurement system (emonPi, emonTx, etc), you must have isolation between the two.
You can use a Hall effect sensor for current, and for voltage by adding a multiplier resistor (though the current the Hall effect device needs to operate poses problems). That will provide the necessary isolation but will need additional power supplies.
And as you know, it is necessary to write your own sketch.
As far as I am aware, there are no plans for a d.c. version of the emonTx, or to add the capability to the emonTx.