237-L Leaf Wetness Sensor

The 237 Leaf Wetness Sensor is designed to emulate the surface area of a leaf. The 237 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 wetdry transition point for the application is also determined by the customer.
Features
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
Specifications
Resistance at WetDry Transition: 50 and 200 kohms (uncoated sensor); normally 20 to 1000 kohms (coated sensor)
For best results, the leaf wetness sensor should be field calibrated since the transition point will vary for different areas and vegetation.