Hello,
Having done some research and for those that don't know the British Gas energy meter (Current Cost CC128) uses a YHDC SCT027H current transformer. Has anyone tried this sensor with emon or could advise me which formulae I need to resolve in order to use it?
Thanks,
Ian
Re: YHDC SCT027H Current Sensor/Transformer
If the YHDC data on their website is to be believed, your c.t. is 150 A : 50 mA, therefore you will be able to use it directly in place of the standard 100 A c.t., but you will need a current calibration constant of 166.66 if you use the standard 18 Ω burden resistor (see http://openenergymonitor.org/emon/buildingblocks/ct-and-ac-power-adaptor...). However, if you are in the UK and have a standard 80 A or 100 A supply, you might want to increase the burden to 27 Ω and the calibration constant is then back to 111.11 again. That will give you a range of 0 - 100 A with better resolution at low currents.
Re: YHDC SCT027H Current Sensor/Transformer
Hi Robert,
Thank you for taking the time to reply, much appreciated.
Yes I am in the UK so would opt for a better resolution at lower currents, as I've yet to see my British Gas energy meter read above 4kW (16A) and if it did I'd probably be having a heart attack at the energy cost ;-) Will also read the webpage you linked to.
Thanks again,
Ian
Re: YHDC SCT027H Current Sensor/Transformer
Provided you remain within the (unspecified and indeterminate) VA rating of your c.t., you can in principle increase the burden resistor even further, but you must bear in mind that if the c.t. sees the fault current when a fuse blows or a breaker trips, you can get a big current spike which might damage the electronics unless the c.t. output voltage or the current into the ADC input protection diodes is effectively limited in some way. (The standard 100 A c.t. in the standard emonTx circuit is just about on the limit!)