An atmometer system based on an analog floating-gate structure and circuit. The floating-gate circuit includes a floating-gate electrode that serves as a gate electrode for a transistor and a plate of a storage capacitor. A conductor element exposed at the surface of the integrated circuit is electrically connected to the floating-gate electrode; reference conductor elements biased to ground are also at the surface of the integrated circuit. In operation, the transistor is biased and moisture is dispensed at the surface. The drain current of the transistor changes as the floating-gate electrode discharges via the surface conductors and a conduction path presented by the moisture. The elapsed time until the drain current stabilizes indicates the evaporation rate.
