OpenEnergyMonitor Community

CT Sensor indicating 11 - 18 watt's when not connected to supply tail!

I have a single SCT-013-000 CT sensor connected to emonpi and have been trying to calibrate with resistive loads ranging from 3kw down to 450W also clamp on amp meter and with some success by editing config file, with the SCT hanging in free space not connected to supply tails its indicating between 14 - 18 watts is this normal or should it be adjusted in the software ?
Otherwise all is working well.
Many thanks,

That sounds a little higher than we normally expect to see. Have you got an a.c. adapter, because that makes a difference. With one, the maths filters out a lot of the noise (it’s noise that you’re seeing), but without it, the maths instead adds in all the noise around.

You can, if the noise is more or less constant, subtract a constant value, but most of the time, the error shouldn’t be significant.

Hi Robert,
Thanks very much for your reply and help.
When you say AC adapter, do you mean the VRMS AC Voltage adapter with UK plug ?
I hope the photos help to show setup and standing watt’s, board and PSU’s and sensors supplied by Glyn 2 days ago.
Thank you for you assistance.

Yes, that’s it. You must make sure that is plugged in and switched on, and the c.t.(s) are plugged in, when you power up the emonPi, because any sensors not plugged in at start-up (and this goes for all OEM kit) are ignored.

If you’re going to put it in some sort of housing, you might find that an earthed metal screen around where the sockets are - but leaving the Pi’s Wi-Fi antenna exposed - might help.

Many thanks Robert, yes the standing watt’s you see in the photo are with everything plugged in and connected at boot up. As long as I know its not a calibration adjustment that’s fine. I will try the shielding later on.
I have messaged Tristan regarding and the app, thanks for that also.
Many thanks,