GPIO Card Surge and Overvoltage Immunity

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  • June 13, 2019 at 4:04 am #27924
    VJC2
    Participant

    We have a project using a Multitech Conduit and MTAC-GPIO input/output module.

    GPIO cards have failed in a number of instances. It is suspected that this is due to overvoltage failures imposed by induced lightning and possibly motor switching surges.

    We have not been able to locate the GPIO maximum input and output specified isolation and surge limits. (We have studied the “GPIO Interface Electrical Requirements” document)

    Would you please advise what the maximum transverse and longitudinal voltages that the GPIO card inputs and outputs can withstand so that we can design proper lighting and surge protection circuits for the various inputs and outputs.

    The installation is in an external semi exposed environment with various distributed sensors connected via cables up to 40 meters in length to the GPIO.

    June 18, 2019 at 4:51 pm #27932
    Steve Kovarik
    Moderator

    Hello Viv

    Regarding the GPIO card.
    All digital outputs have TVS protection (transient voltage suppression)up to 70 Volts peak for 10ms.
    Digital inputs are optical-isolated (no TVS) with diode protection up to 70 Volts (for 10ms) peak pulse 50mA.
    Analog input supports 0-5VDC direct to op-amp with no protection.
    Opto Isolator Isolation voltage level is 3750 Vrms.
    On the MTAC card, the EXT_IN_GND pin is fully isolated from all other grounds.
    Clearance of the EXT_IN_GND on the MTAC-GPIO board is only 25 mils.
    Because of the size, the MTAC-GPIO was not designed for high voltage isolation.
    The ANALOG_IN_GND pin is connected to the Conduit GND through a ferrite bead.

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