The 237 is intended to emulate a leaf surface, it is primarily used to determine the percentage of time that a surface (i.e., leaf surface) is wet versus dry.
The measurement is made by determining the electrical resistance on the surface (a wet surface is less resistant). The 237 is shipped unpainted; the customer determines the appropriate paint to apply to the sensor's surface (see manual). The wet/dry transition point for the application is also determined by the customer.
Following calibration by user, detects periods of leaf wetness caused by rainfall, dew, or spray
Measures electrical resistance between interlacing gold-plated fingers on circuit board
Size and smoothness of sensor emulates surface area of leaf