From: Josh Tetarenko <tetarenko.josh@gmail.com>
    Date: October 7, 2019 at 9:50:30 AM PDT
    To: DJ Osborne <djo@mbari.org>
    Subject: Re: DTEC GFI board

    Hi DJ,

    The sense blocks are very simple. Heres an explanation from the website, a schematic, and picture of the actual block. It’s really just 2 high impedance resistors, so you can build your own if you want. Especially just for 220VAC.

    2.4 Sense Blocks:
         A sense block is required for each channel to be monitored and sense blocks may vary from circuit to circuit due to the type of circuit to be monitored.  It is essential that the proper sense blocks are used in each circuit or incorrect and faulty readings could result.  The input resistance the sense circuit requires for proper measurements is 600 Kohm, therefore; in a DC or 1 phase AC circuit the 2 resistors must be 1M2. In a 3 phase AC circuit the 3 resistors must be 1M8.  For monitored circuits up to 1000 volts use 1/2 watt resistors, for monitored circuits up to 2000 volts use 1/2 watt resistors and for monitored circuits up to 3000 volts use 1 watt resistors.  Try to keep the sense blocks close to the high voltage and use 22 to 16 gauge wire for the sense wire to the GFM unit.  This keeps the high voltage within the designated area.  For connection examples see appendix A.  The resistors must be appropriately voltage sized.



    Let me know if you have any more questions.

    Thanks,
    Josh


        On Oct 4, 2019, at 7:39 AM, DJ Osborne <djo@mbari.org> wrote:

        Hey Josh,
        I do have a question…
        Can you define what you mean by Sense block regarding the higher voltage than 120 VAC.
        We have a 220 VAC circuit and would need a sense block for that sense line but we are not entirely sure what the sense block entails.
        Thanks so much,
        dj