Mark,

i see, i thought it would just connect onto the signal wire of FRP sensor and calculate pressrue via voltage output.

Somewhere on one of the forums someone posted some software that calculated expected pressure from voltage output depending on system type.

Now this may be a stupid suggestion or even dangerous which is where someone like you would know more but as the Sykes Pickavant gauge is rated to 1700bar why couldn't it be used whilst engine is running.

If you were to disconnect an injector pipe at common rail and insert the gauge onto the outlet then you'd have a running pressrue at idle.

This then could be compared to live data FRP.

I don't mind being corrected as its only a question rather than something i'd recommend unless it was actually accepted as valid test with the equipment.