A thermal conductivity vacuum sensor with a novel on-chip control system is presented. The sensing structure is a small circuit suspended over a cavity etched in the substrate. An integrated control system maintains a constant temperature difference between this thermally isolated sensor and the substrate. The control loop allows for a digitally adjustable operating temperature of the sensing structure. The range of the vacuum sensor extends from 0.8 Pa (6 mTorr) to approximately 9.2x10⁴ Pa (690 Torr). The system was fabricated in a completely unmodified foundry CMOS process, dissipates only 5 mW of power, and occupies an area of approximately 0.3mm².

Klaassen, E. H., and Kovacs, G. T. A., "Integrated Thermal Conductivity Vacuum Sensor," Sensors and Actuators A, vol. 58, no. 1, Jan. 1997, pp. 37 - 42.