US Patent 8955367 Gas sensor with compensations for baseline variations

Reliable, fast and inexpensive breath gas detector systems for medical diagnostics, including personal, handheld monitoring devices for a variety of diseases and conditions, including, for example, asthma, diabetes, blood cholesterol, and lung cancer. A sensor device (100) for detecting gases includes a sensing element (109) having an electrical resistance that changes in the presence of a target gas; a readout circuit, electrically coupled to the sensing element due to the presence of the target gas and converts the measurement to a digital signal; and a feedback loop (203) from a digital unit (205) to the readout circuit to compensate for variations in a baseline resistance of the sensing element.