Is the NI9481 internally protected against a short?

[ecoandy]

Greetings,

I use the NI9481 to turn on / off 120 VAC heat tape. On rare occassions, this heat tape becomes wet, shorting the narrow gauge wire within the tape. When this heat tape is plugged directly into a 120 VAC GFCI plug, the GFCI trips. What will the NI9481 do? I just purchased some cheap protable GFCI plugs, but these, of course, need power all the time to remain active. If I toggle power using the NI9481, the GFCI turns off, only to be manually turned back on. Thank you for your thoughts.

andy

[DJColeslaw]

Can you provide some specific information about exactly how everything is connected? Where is the 9481 in association with the GFCI and the heat tape?

[ecoandy]

Thank you. Yes. The heat tape (which is one continuous narrow gauge wire in a loop) terminates in a two-prong AC plug (no ground). One side is wired to one of the terminals on the NI9481 (CH0a for example). The CH0b side of the NI9481 has the hot line of 120 VAC source. The other side of the heat tape is wired to the neutral line of the 120 VAC source. No GFCI is involved and this setup works great. I can easily turn on and off the heat tape. The application I am about to start, however, runs the risk of having wet heat tape from time to time. When I run this application manually, without the NI instrument involved, and have the heat tape plugged into a GFCI plug, if the heat tape becomes wet, the GFCI simply trips, I wait for the heat tape to dry, and carry on. I am afraid I will blow the NI9481 or worse, if I don't protect it...as I don't know if its internally protected. Good?

[DJColeslaw]

It sounds like your setup should be ok.  However, the card is rated for 250Vrms continuous or 1400 Vrms instantaneous at 2 Amps, which isn't likely in this case, espeically with the GFCI plug.  The system failure would need to be characterized by a qualified Analog Engineer to determine what the maximum possible fault levels are to determine an absolute answer