Apologies up front, I'm a process engineer. Our client wants to use a single transmitter for a HH and LL output to ESD for compressor suction pressure.
Is this possible, permissible or should there be two separate transmitters, one for HH and the other for LL?
Do you know why your client prefers a single transmitter and what precisely is the device.
One way round the subject is HAZOP meeting where the fail safe / fail to danger and the implications can be discussed at length.
If the process impacts, the safety impacts, equipment damage and the production loss impacts from a false trip or a failure to trip are low enough then it's OK.
If impacts are high as determined by a HAZOP then using a 2oo3 transmitter arrangement is recommended.
3 transmitters with different 2oo3 logic for each high or low trip.