A capacitance-based pressure sensor for measuring a process variable includes a metal sensor body, a diaphragm disposed within a cavity of the metal sensor to form a deflectable capacitor plate, and an insulator extending through the metal sensor body from an end wall to the cavity. The pressure sensor further includes an isolation tube in fluid connection with the cavity, the isolation tube extending into the insulator through the end wall, a stationary capacitor plate on a surface of the insulator in the cavity, the stationary capacitor plate spaced from the diaphragm, and an electrical lead wire connected to the stationary capacitor plate and extending through the insulator parallel to the isolation tube and exiting the insulator at the end wall. A fill fluid is within the isolation tube and the cavity to apply pressure to the diaphragm.