Time- and Level-Controlled Filling System for Class A Evaporation Pans

Recently developed integrated circuit technology and new reliable pressure transducers have made it possible to develop a battery-operated system to automatically fill class A evaporation pans from stored water. The system records and stores the average of 12 pan level records during a 1 min time period at the end of each every 15 min period for later transmission to a central data storage facility. The measurement sensitivity of the system is 0.02 cm of evaporation over a range of 3.5 cm. A field calibration of the system showed that there was a very good (\iR²=0.999) linear relationship between standard hook gage and pressure transducer water level measurements. This system is being used in remote locations because the circuitry draws very little quiescent current. A small solar panel keeps the system’s 12 V battery fully charged.