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Last Post 06/06/2013 8:52 AM by  Tim Mik
CR4395 with CRGFS-100 Application Question
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Tim Mik
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06/04/2013 1:45 PM
    Is there a limit to wire length from a CR4395 Module to the CRGFS-100? Also should shielded cable be used for interconnection? Thanks, Tim
    Tony Hodges
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    06/05/2013 9:11 AM
    Dear Sir,

    The secondary of an AC current transformer such as the CRGFS-100 is modeled as an AC current source. As such, increased resistance from longer wire lengths causes the current source to increase its voltage output to maintain the current level. Therefore typically you can add wire length up to the point where the CT can develop enough voltage. The burden presented to the CRGFS is quite high, so adding wire with a series resistance of less than 10 ohms should perform adequately.

    As for shielded cable, this would help to limit common signal errors (same error on both wires), but typically since the signal is a current, a twisted pair is sufficient for minimal noise figure.
    Tim Mik
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    06/05/2013 10:06 AM
    OK Thanks Tony. Another question regarding the original post...

    I am using 2 CRGFS-100s in series and am hanging one on 2 of the legs of a 3 ph diffusion pump heater circuit to alert if one of the heater elements opens. It works fine, but I notice when putting 2 of the CRGFS-100s in series they seem to have a "polarity"? In other words I notice a difference in current by swapping leads. Do these current transformers typically react like this?
    - Tim
    Tony Hodges
    CRM Staff
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    Basic Member
    Posts:154


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    06/05/2013 4:30 PM
    Dear Sir,

    When adding or paralleling 2 AC signals, they can be either in phase or out of phase. You are seeing this characterisitic.
    Tim Mik
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    06/06/2013 8:52 AM
    OK Thanks. I appreciate the assistance. -Tim
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