Configure Output formula


#1

Hi,

Had my IoTaWatt for a few days now and starting to get to grips with it. However I am trying to setup an Output formula which does not work. My house is off-grid and has a solar array. The main house feed from the inverter shows a negative value when the power is coming from the batteries and positive figure when the PV is supplying extra power that is going to the batteries. I need/would like this to be the other way around.

I tried a very simply output formula (Main) x -1 to reverse the signage but this just returns zero (so me thinks a bug), changing it to x 10 or something does work. Basically multiplying by a negative number false.


#2

Appears to be. I have no trouble recreating it. Seems to be that the unary minus on a constant is not working. I’ll fix that.

In the meantime, you need a workaround. You can generate the -1 constant using the binary minus operator:

Main x (1-2)

Sorry about that, will be fixed in a later release.


#3

Thanks, and can confirm that (1-2) fixes the problem as well. I now have negative power on this nice sunny day.


#4

Does just:
0 - Main
work?
(Probably negligible, but technically subtraction is usually more efficient than multiplication)


#5

That should work fine. The problem was that a negative constant wasn’t parsing. So yes, in the case where you want to multiply by -1, simply subtracting from zero would work.