Temperature-compensating absolute pressure sensor

An absolute pressure sensing system comprising:

• a first pressure inlet configured to couple to a process fluid;
• a second pressure inlet coupled to a reference pressure cap, wherein the reference pressure cap comprises a quantity of gas at a reference pressure within a piston;
• a differential pressure sensor coupled to the first and second pressure inlets to measure a difference in pressure between the first and second pressure inlets;
• a first piston area exposed on the piston;
• a second piston area exposed on the piston;
• and
• wherein the piston is configured such that a ratio of the first piston area and the second piston area has a relationship to a ratio of atmospheric pressure and the reference pressure within the reference pressure cap.

A conversion mechanism configured to couple to a differential pressure transmitter, the conversion mechanism comprising:

• a piston;
• a first piston area exposed on the piston;
• a second piston area exposed on the piston;
• a coupling feature configured to couple the conversion mechanism to a low pressure inlet of the differential pressure sensor;
• wherein the piston is configured such that a ratio of the first piston area and the second piston area has a relationship to a ratio of atmospheric pressure and a reference pressure within an absolute pressure cap;
• and
• wherein, when coupled to the differential pressure sensor, the piston is configured to contain a known volume of gas at the reference pressure, and wherein the piston, upon mechanical actuation, reversibly change in response to a change in ambient temperature such that the reference pressure is maintained within the piston.