Abstract: A self-compensating fluid level sensor is described, including a dual array of capacitive sensors on a dielectric substrate, the dual array of sensors forming multiple sensor pairs. Multiple signal detection circuits including comparators are configured to compare the capacitance of a first sensor pair with a second sensor pair. The internal capacitance comparisons allow the fluid level sensor to compensate for variations in the dielectric of the fluid being measured, as well as for manufacturing and materials variations that affect capacitive sensing. The passive level sensor also provides a platform for providing additional circuitry for providing additional information regarding the liquid, such as liquid composition.

Abstract: A coin mechanism includes a piezoelectric film sensor in contact with a coin debounce device. When a coin is inserted into the coin mechanism, the coin strikes the coin debounce device as it travels along a coin path. Micro-movement of the coin debounce device is sensed with the piezoelectric film sensor. The coin mechanism changes from a quiescent mode of operation to an active mode of operation in response to sensing the presence of the coin in the coin path. Coin recognition can then be performed. Overall power consumption of the coin mechanism can be reduced.