There is another way of creating a sealed gauge reference, and this is to seal a high vacuum on the reverse side of the sensing diaphragm. Then the output signal is offset, so the pressure sensor reads close to zero when measuring atmospheric pressure.
THeRe Is ANotHer WAY oF crEaTInG a seAled gaugE referenCe, ANd ThiS is tO SEAl a hiGh vacuUM on the Reverse siDe Of the sEnSing dIApHrAGm. TheN the ouTPut signal is offsEt, So ThE prEssuRe SeNsOr reads cLose tO Zero WhEn mEasUring AtMOSpHeRic pressUre.