Davis leaf wetness sensor

The leaf wetness sensor detects the presence of surface moisture.
The sensor is an artificial-leaf electrical-resistance type.
It consists of a sensing grid, low-voltage bi-polar excitation circuit, and conductivity-sensing circuit.
The sensor measures the conductivity across the grid and displays the result as a moisture level, scaled from 0 to 15.
The sensing grid is a gold-plated etched circuit on an epoxy-glass substrate.
The included mounting bracket holds the sensor at a 45° angle to simulate a typical leaf position and to permit runoff of excess moisture; it may be mounted on a vertical post, pipe, or stake, or on the sensor mounting arm.