datasheet claims relay output is "Form A - Normally Closed"

[defcon.klaxon]

Hi all,

A client is asking if I can move a motion sensor from an existing alarm dialer to a PLC discrete input. Looking up the datasheet, it says that the relay output for the alarm is "Form A - Normally Closed". But doesn't the very definition of Form A normally open? Am I missing something?

http://www.ntsupply.com/files/products/ge_sentrol_6000_series.pdf

 

[OkiePC]

Yeah, it probably should say "Form B", but it's a relay so wire it up, test it, program and label accordingly.

 

[defcon.klaxon]

Yeah, it probably should say "Form B", but it's a relay so wire it up, test it, program and label accordingly.

Yep that's the plan. Just wanted a sanity check to make sure I wasn't missing something. Thanks!

 

[GaryS]

Form A is Normally Open
Form B is Normally Closed
Form C is Both
I thin what they mean is the relay is a Form A N.O.
the relay is energized and held closed I normal operation in an alarm condition the relay deenergized and the output is turned off kind of like a fail safe if the device is not powered then it would set an alarm in whatever control is monitoring it.

 

[OkiePC]

Form A is Normally Open
Form B is Normally Closed
Form C is Both
I thin what they mean is the relay is a Form A N.O.
the relay is energized and held closed I normal operation in an alarm condition the relay deenergized and the output is turned off kind of like a fail safe if the device is not powered then it would set an alarm in whatever control is monitoring it.

I concur. Back in the olden days we called them NOHC contacts (normally open, held closed).

 

[defcon.klaxon]

Thanks GaryS and OkiePC, that makes a lot of sense!