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I'm using this CT for current monitoring. It is a split-core current transformer. It just plugs around the phase load wire. I was using this with a breadboard circuit and it works fine. I'm doing a PCB now and I have decided to go for this, It's a vertical PCB mount current transformer. It's a through-hole component. Also, the phase wire is a copper trace.

Do you still have to pass the phase wire through the CT or just trace the phase wire to one of the terminals of the PCB mount CT? Any suggestions will be helpful.

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  • \$\begingroup\$ You would have to make a wire loop through the CT's orifice. For measuring on a PCB, something like the ACS758 is more suitable. \$\endgroup\$ – venny Sep 14 '15 at 21:34
  • \$\begingroup\$ Thanks. Suppose I use CTs, I need to connect the output from the CT to two input terminals, positive and negative. Is there a way I can determine the positive and negative terminals from the CT (in the second link) or it doesn't matter? \$\endgroup\$ – am3 Sep 14 '15 at 21:37
  • \$\begingroup\$ Not on this particular one, but others (e.g. from Murata) have polarity marking. It makes little sense anyway, since it measures AC current which is symmetric around zero. \$\endgroup\$ – venny Sep 14 '15 at 21:48
  • \$\begingroup\$ I agree but I thought it will screw up the polarity and I'll get negative energy readings. (I'm feeding this to an energy IC) \$\endgroup\$ – am3 Sep 14 '15 at 21:49
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I have used this sort of transformer in PCB layout before. A couple things to note:

  1. Regardless of how you design this, the primary current you want to measure must pass through the hole in your CT. The secondary side (the pins that land in the PCB) are the output of the CT.
  2. Since these are low frequency CTs, however you lay them out will probably be OK, provided your schematic is functionally correct.

Depending on your design, there are a couple ways to get the primary current through the CT:

  1. Run your primary wire directly through the CT hole: This is the most obvious, and perhaps one that you wish to avoid?

  2. Provide a terminal block or some other two-pin connector on your board that has two traces run to either side of the CT. A wire or metal clip can then be installed through the CT hole to complete the primary side connection. This is the method I’ve used and have had good success.

Without further information on your application or other design considerations, it’s hard to give other ideas. Good luck!

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  • \$\begingroup\$ Thanks. This helped. I'm feeding the output from the CT to an energy IC which has a positive and negative input for the CT. Is there a way I can evaluate which pin is positive and negative (or does this matter)? \$\endgroup\$ – am3 Sep 14 '15 at 21:45
  • \$\begingroup\$ The output of the current transformer will be AC. If you get the polarity (really phase) wrong, the energy IC may give a negative reading - if so, just pass the primary wire through the hole in the opposite direction to correct the phase relation. \$\endgroup\$ – Peter Bennett Sep 14 '15 at 22:03
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My answer is in the same vane as @Dweeberkitty's answer above. I only want to add a photo.

enter image description here
(bigger picture)

The primary wires go through the hole in the middle. To save cost, they are soldered directly to the PCB. There are 2 wires on the primary side, because this transformer is intended to sense the difference between the 2 currents flowing in opposite directions.

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  • \$\begingroup\$ Awesome. Thanks. Did the polarity of the pins of the CT matter? \$\endgroup\$ – am3 Sep 15 '15 at 1:45

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