Patent ID: 8869586

Claim:
A method of calibrating a chemical sensing system that detects a presence of a substance, the method comprising: at a first time, activating a first chemical sensor that is configured to provide sensor values responsive to the presence of the substance such that the first chemical sensor is configured to detect the substance when active; at a second time that is subsequent to the first time: activating a second chemical sensor that is configured to provide sensor values responsive to the presence of the substance such that the second chemical sensor is configured to detect the substance when active, and determining, by a processing device, a first sensor value associated with the first chemical sensor and a second sensor value associated with the second chemical sensor, wherein the first sensor value and the second sensor value are obtained at the second time; at a third time that is subsequent to the first time and the second time: determining, by the processing device, a third sensor value associated with the first chemical sensor, and determining, by the processing device, a fourth sensor value associated with the second chemical sensor; and determining, by processing device, a calibration value based on the first sensor value, the second sensor value, the third sensor value, and the fourth sensor value.