CT clamp precision using EmonTx v3 with batteries


I'm using EmonTx v3 with batteries, EmonHub (Raspberry) as gateway and I'm monitoring gathered data on EmonCms. Everything works great, but the precision seems to be very low.

When I switch off the appliances which I'm monitoring, the received data are not zero but 30W in CT1 and 10W in CT2. There is not current but these values are shown.

I know that using EmonTx with batteries decrease the precision, but it is really too much imprecise.
Can I improve this precision somehow?

Robert Wall's picture

Re: CT clamp precision using EmonTx v3 with batteries

The use of batteries, provided that there is enough voltage for the regulator to continue to operate properly, won't affect the precision. What you are seeing is almost certainly noise from the digital circuits inside the processor leaking in to the analogue input. It will be worse if you are not using the voltage input, as the rms calculation on the current rectifies the noise. 30 W and 10 W are only about 0.1% and 0.04% of the maximum reading. If you wish, and that noise figure is roughly constant, you could alter the sketch to subtract that value, or you could subtract it in emonCMS if you prefer.

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.