Calibration Problem

can it possible ?(sic)

No, not unless you can afford to send your transmitter into space.

I said that as a joke but it is entirely true. No vacuum pump can produce zero absolute pressure so zeroing your transmitter is impossible. I faced the same problem several years ago when we were setting up our calibration lab in our factory.

My solution was to calibrate the transmitter at 0 to 1 barg (bar gage). Then I reranged the transmitter back to 0 to 1 bara (bar absolute). Later, I asked Foxboro online support if this was okay and received an affirmative reply.

regards,

Vulcan

Dont know if your application allows, but you can invert the output scale, consider zero in the ambient pressure and allow it to go down with vacuum. So, consider zero as full scale level and you have your zero trim, but with an actual offset of 14.69 psia or so. Depends on the way you see or call the value.