Attaching CT's and emonGLCD

I'm in the US so having to deal with that. I have 2 Magnelab SCT-0750-000 CT's I understand that I should attach them to the two feeds in opposite direction and then sum the inputs in emoncms. Right? I haven't been able to find any docs on what operations are permitted - where? I can't find any docs on emoncms and the internal docs page shows nothing.

So my question is how to I ensure that they are connected so they sum correctly? Or can I just attach the CT's and then process the inputs to produce a positive value? Or does it not matter which way they are connected just so they are backwards of the other? These things are more difficult to pull apart then I thought and I don't relish having to do it once they are installed with a powered breaker box (or is there some trick?). Or is it that because the two feeds are 180 deg out of phase, that reversing one also reversed the output voltage so summing makes sense?

Another question on emonGLCD - since I have 2 feeds, how to I sum that on that device? And does it have an auto dimming capability so the display is off at night, say from midnight to 8am?

Also as a comment, I tried the USB_HDD script to move the OS to my HDD. It worked except that it didn't update the cmdline.txt and fstab files. I was able to do that on my own. Not sure why it didn't work.


Bill Thomson's picture

Re: Attaching CT's and emonGLCD

Hello from Oklahoma. I use Magnelab CTs too, so can relate to the difficulty involved in pulling them apart.

Here's info that should help.


Robert Wall's picture

Re: Attaching CT's and emonGLCD

Have you seen the Resources page about installations in N.America? That should give you a fair bit of background information about how to connect your CTs.

I can't give a detailed answer about further processing because you haven't said what is in between the CTs and emoncms, nor indeed which emoncms you're using.

If your emonGLCD receives a time feed from a server somewhere - either or your own - then, depending on the sketch, it can control the backlight according to ambient light, and it can turn the backlight off overnight (you'd need to check the sketch that you intend to use for the details).

Assuming that your emonGLCD receives its data from an emonTx, then (again depending on how you connect your CTs) you might need to modify the sketch to add the powers inside the emonGLCD.

[OK, Bill T typed rather less than I did!]

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