19 



to wetting and drjdng before it is calibrated. Proceed as follows: 



1. Press the sensor indicator switch. 



a. If the LED glows, proceed to (2). 



b. If the LED does not glow, loosen the tension-adjustor bolt 

 and slowly turn the knob clockwise until the LED glows. 

 Now proceed to (2). 



2. Loosen and turn the tension adjustor knob counterclockwise 

 slowly until the LED stops glowing, then release the sensor 

 indicator switch. 



3. Spray the wetness sensing element evenly with a fine mist 

 until it is thoroughly wetted. 



4. Press the sensor indicator switch. 



a. The LED should be glowing within a few minutes after the 

 element has been wetted, indicating that the element has 

 responded to wetting. If the LED is glowing, release the 

 switch and proceed to (5). 



b. If the LED fails to glow after several minutes, the fault is 

 with the sensing element. Either 'recondition' the element 

 or attach another 'conditioned' element. If the elements 

 continue to fail to respond, another type of cotton line or 

 perhaps degreased hemp will be necessary. Once the 

 proper element has been found, proceed to (5). 



5. Allow the sensing element to dry, then push the sensor indi- 

 cator switch. 



a. The LED should not glow, indicating that the sensing 

 element has returned to its original tension. Proceed to (6). 



b. If the LED continues to glow, then the element has not 

 responded properly to drying. Either the element needs 

 further 'conditioning' or, if that fails, another type of line 

 is necessary. Once the proper element has been found, 

 proceed to (6). 



6. If the element has responded properly to wetting and drying, 

 turn the tension-adjustor knob counterclockwise to further 

 ease the tension on the sensing element. Repeat STEPS 1-5. 

 Repeat several times until you find the limits of the sensing 

 element's capacity to respond to wetting and drying. This 

 should help in deciding the level of sensitivity (response to 

 condensation and precipitation) that can be expected. 



NOTE: This testing procedure should be performed periodi- 

 cally (perhaps once a month) to make sure the element 

 is continuing to respond properly. 



Calibrating the Leaf Wetness Indicator 



The sensing apparatus must be adjusted so that the leaf wetness 

 indicator will be activated only during the time interval when leaf 



