I have an emonPI, emonTX and Heat Pump Monitor that I want to use together.
All of the devices I mentioned above have CT sensors connected.
If I want accurate Real Power Measurements to be made with all of them do I need a separate 9V AC-AC adapter power supply for each, or is it enough to have one connected to the emonPI because the devices can share the measurements?
If I connect a 9V AC-AC adapter power supply to the Heat Pump Monitor does it also need a separate USB power supply?
Can I use the emonTH for measuring outside temperatures?
If yes how should I place it to make sure it is not damaged by weather?
No - each device does the real power calculations internally, so all need the a.c. reference. But, provided you use a common d.c. supply, you can have a common a.c. reference to the emonTx and the emonPi, but the Heat Pump Monitor uses a different input circuit, so it must have its own a.c. adapter. But it can share the 5 V d.c. supply.
The best way, if you are only interested in temperatures, is to have the emonTH indoors and use a separate encapsulated sensor outside, taking the cable out through a small hole in a convenient place.
Otherwise, you need to obtain (make?) a Stevenson screen (obviously not that big) to protect it from precipitation but allowing free air movement.
So according to this the Heat Pump Monitor requires both the 9V AC-AC adapter power supply and the 5V DC USB power together, unlike emonTX that does not need the 5V USB power when 9V AC-AC adapter power supply is connected to it?
Correct - but if you have a 5 V supply, the emonTx (and the emonPi if it uses the same a.c. adapter) will be more accurate if the emonTx takes its power from the d.c. supply. This is because the emonTx ‘dents’ the voltage wave as it draws power near the peak of the positive cycle, causing a small inaccuracy.