I am trying to put together a energy monitor using emontx3.4 schematics (atleast for the CT portion).
I looked at the schematics here: https://raw.githubusercontent.com/openenergymonitor/Hardware/master/emonTxV3/emonTx_V3.4/schematic.jpg
Each CT has its own voltage divider, is there a reason this is not shared?
Can I share it with 4 CTs in my setup?
Do I need an op-amp to share? (If yes, why? would help me learn also :)) I am not super familiar with electronics so please excuse the beginner level question.
Thanks
Re: Sharing the voltage divider in emontx 3.4 schematics
No personal experience, but I believe others have reported that you can share the mid-rail if it's driven by an op-amp. If you attempt to share it with just the R-divider, then you'll get interference between the channels.
Re: Sharing the voltage divider in emontx 3.4 schematics
"Each CT has its own voltage divider, is there a reason this is not shared?"
The most likely reasons are crosstalk and cost. You need that centre voltage to stay constant to within a millivolt or so, and using it for many channels could mean one 'pulls' the voltage thus coupling itself to all the channels. To get round this, you need an op.amp that gives you a low impedance output that cannot be pulled about easily. That would add to the cost and the current drain, making battery operation expensive.