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E-HELP: Configuring the STA for Multiple Pressure Levels

E-HELP: Configuring the STA for Multiple Pressure Levels

Q: I need to use the STA Safety Trip Alarm in a hardwired panel. Is it possible to configure two different levels of alarm for each of two relays in the STA, in order to have two different trips (one for each relay)?

A: Only one set point can be assigned to each alarm relay of the STA. However the dead-band is adjustable from 0% to 100% of the input span. Therefore you can specify one signal level at which the relay engages and another for when it disengages.  If your input signal is 4-20mA, you can connect it in series to the inputs of two STAs in order to obtain 4 independent relay/setpoints.

Q: To clarify my situation: if I have a 0 to 100 bar transmitter, can I trigger Relay 1 at 25 bar and Relay 2 at 75 bar? We need to do this in order to shut down two different pieces of equipment at these pressure levels.

A: This is a typical function of the STA. One relay setpoint is often used for a warning at one level while the second relay setpoint is used for shutdown at the next level.

Published: October 21, 2015
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