AC current metering

[docwisdom]

I searched the subject and read up on a few forms. Now for some things a little more project specific.

I am looking to meter about 10 AC sources inside a mains panel, all 120v/20a max. I have checked out some current transformers. It looks like the wire lead ones would work the best so then I could run the leads outside the panel to the PIC meter. Can the transducers hang there on the source cable or do they need to be hard-mounted? I have been a bit confused by the different specs on the transformers, what would you recommend for this application?

regarding the PIC, what chip would you recommend for reading up to 10 transformers?

finally, could you point me to any sample code to get my headed in the right direction?

thanks!

[Charles Linquis]

Current transformers will work, but I have abandoned them in favor of the Allegro hall-effect sensors. Very linear and not as susceptible to noise on the lines.

[docwisdom]

Thanks Charles.

I looked at allegras site
http://www.allegromicro.com/en/Products/Categories/Sensors/currentsensor.asp


Could you explain how you would physically mount these in my situation? The current transformers are pretty easy, wire goes through the hole. In my application I need something that doesn't interfere with the source path.

Also could you recommend a specific model#?

[Charles Linquis]

We mount them on a PCB. The model depends on the maximum current. We use the ACS752, but then we are measuring some really high currents. If you need devices that
have mounting screws, you can find those at -

http://www.sypris.com/stm/content.asp?page_id=812

[MarioC]

The model depends on the maximum current. We use the ACS752, but then we are measuring some really high currents.


50 to 100 amps (that's pretty high).

[docwisdom]

Again I need a solution that is physically isolated from the source path. This is why I was looking at the current transformers.

[dhouston]

Again I need a solution that is physically isolated from the source path. This is why I was looking at the current transformers.
The Allegro chips provide electrical isolation of several kV. I'm not sure what you mean by physically isolated.

[Charles Linquis]

Yes, they are isolated.
I have used both current transformers and Allegro devices, and I only use the Allegro parts now because of their size, accuracy and ease of use. Even though I mostly use the larger devices, I have used their smaller parts (SOIC-8 package) to measure currents below 100mA.

[docwisdom]

from what I can see the circuit to be sensed needs to be cut and routed through Ip- and Ip+on the allegro devices.
I need something that does not disturb the circuit to be sensed.

[Charles Linquis]

That is true. Looks like you want a clamp-on current probe. I can't help you there. Sorry!