A low cost automatic data acquisition system was developed for modified Bellani plate atmometers or ET gages (ETGs) that consisted of a float and pulley system with an optical encoder and a low cost data logger that detected switch closures. The system cost was approximately $200 to retro-fit an existing ETG. Laboratory testing of this system indicated that errors were in the range of errors reported for lysimeter data versus Penman Montieth ET o estimates and within the range of errors reported for ETGs compared to ET o estimates. The float and pulley system performed better under conditions of 4-6 mm ET during an increment (i.e. day) because errors associated with manual reading of the site tube were minimized. Future work on the system should include field testing.
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