Simple pressure switch circuit using standard MS MAP sensor?

[Quagmire]

Wasn't sure where to post this so here goes.

I want to build a stand alone circuit that i can use to trigger a relay when the line pressure on my LPG injectors drops below a (yet to be determined) threshold value.

The idea is that the relay will override the LPG master switch and cause the vehicle to fall back to Petrol running.

I have a spare MAP sensor lying around, is there anyway I can use this to drive such a circuit?

Key points I guess are:

1) The trigger value for firing the relay needs to be adjustable at the moment, until I can do some datalogging and determine what pressure drop causes AFR's to change too much and therefore need a switch back to petrol.

2) The MPX4250A needs a 5v input, so a voltage regulator will be required.

Any suggestions on which way to go are gratefully recieved.

Many thanks!

[Matt Cramer]

Sounds like you're looking for a simple comparator circuit.

[Quagmire]

Thanks Matt, so from some googling something like an LM393 would be needed then?