• # Need some help/information on AC Current sensor

just ordered three.
let’s see if i’m able to deal with them

found a website named http://openenergymonitor.org where this ct sensor is used
maybe this helps somehow, lets see.
http://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface
otherwise trial and error

pimatic v0.9 has been released!
Support Pimatic and get some free stickers

make it so !

• This links show you all what you need.
We get it working.

pimatic rocks!!!

• How do you calculate the Watt?

Normaly it is only the current of 1 or maybe 3 phases but you miss the Voltage. Ok you can use 230V as nearly const.
Additionally you will never have W as output, it is V*A what means VA and is not the same then Watt because Volt and Amp will never have the same timing!

Exept heatings from washer or hob/ofen nearly everything in a modern house is with electronics an will give you big difference between Watt/VA values.

• I suggest to calculate like this volt * ampere * cos phi = watts
I’m having an energy meter for the attic. there i can see the cos phi for just this one phase. it’s about 0.9 to 0.95. I’m assuming the cos phi with 0.9 so it would be 230 volt * 5 ampere * 0.9 = 1035 watts.
could that be a correct calculation for that or do you have a better suggestion? don’t know how the phase shift will be when switching on televisions or other electrical loads at the other phases for the livingrooms.

The 5 ampere are just suggested for a calculation example.
If all fails I’ll be fine with the VA since it’s higher settled. So I’m having some buffer.

pimatic v0.9 has been released!
Support Pimatic and get some free stickers

make it so !

Yes shure, the calculation with “volt * ampere * cos phi = watts” is Ok, but you never know “cos phi” as a const value.
If it’s not important to know precise values this is a good way. Differences maybe sometimes more then ±20% from real Watts!
By the way, cos phi you measured at one place is only valid for devices powerd by the current through this meter.
Devices outside of this current loop, even at the same phase will have totally different cos-phi.

A good measurement would be with real analogue multiplier (OP) for V*A or by sensing both at same time with higher frequency and calculate the pairs of values. And with 3 Phases you need all that 3 times.
That’s why real power meters not very cheap.

• +/- 20% is lots of stuff at higher loads.

pimatic v0.9 has been released!
Support Pimatic and get some free stickers

make it so !

I can’t give you better values but that’s the possible fault I expect.
For example an standard neon tube alreday has a cos-phi on about 0.5, and will give you very different values on Watt and VA.
If your main load is one big heating there shouldn’t be any difference between Wattt and VA because it’s only straight resistance.

• sure, i understand. let’s first see if it works at all
still waiting for some parts to be delivered

pimatic v0.9 has been released!
Support Pimatic and get some free stickers

make it so !

• no news on that project by now. having all parts together but the curent sensors.
unfortunately the German vendor ran out of stock for these, so i had to order in china now

pimatic v0.9 has been released!
Support Pimatic and get some free stickers