A method of self-calibration for integrated capacitive sensors

In a sensor employing changes in capacitance the introduction of two additional reference electrodes can assist in the minimization and correction of errors introduced in the manufacturing process and from changes in environmental conditions. The two extra electrodes that reflect the maximum and minimum values of the measuring electrode are constructed during the same lithographic process and in close proximity to the active electrode. In preliminary trials of 79 sensors the uncorrected error in reading was nearly 20% of full scale and dropped to 4% of full scale after applying the correction. The technique with support electronics printed on flexible substrates allow the sensor to be small, integrated and "smart".