27 

 FIGURE LEGENDS 



FIG. 1 . Recording of environmental variables by the A) 4-pen arm 

 and B) 3-pen arm hygrothermographs. 



FIG. 2. Major components of the field instrumentation: rain col- 

 lector (ai); digital counter (ag); leaf wetness indicator (b); 

 hygrothermograph (c). 



FIG. 3. Diagram of tipping-bucket assembly of the digital rain 

 gauge. Cutaway view showing magnet (a); magneswitch 

 (b); adjusting screws "B", and adjusting screw "A". 



FIG. 4. Leaf wetness indicator with cutaway view of the LWI 

 sensor relay: wetness sensing element (a); sensor relay (b); 

 sensing element tension-adjustor (c); LWI housing (d); 

 light emitting diode (LED) (e); sensor-indicator switch (f). 



FIG. 5. Diagram of sensor relay in the A) "dry" position and B) 

 "wet" position: contact plate (Cp); copper contact (Ci); 

 attachment for sensing element (a). 



FIG. 6. Schematic representation of the 4-pen arm unijunction 

 assembly circuitry: Ri = 220Q; Rg = 470kO; R3 = 4.7ka; Ci = 

 500 UF; Ti = ECG6 401; K^ = 12 VDC relay. 



FIG. 7. Steps in preparation of the LWI and rain-intensity pen 

 arm relays. (Letters refer to steps explained in text) 



FIG. 8. Steps in construction of the LWI and rain-intensity pen 

 arms and attachment to the pen arm relay. (Letters refer 

 to steps explained in text) 



FIG. 9. Diagram of location of the plexiglass base on the 4-pen 

 arm hygrothermograph. 



FIG. 10. Diagram of dimensions for constructing the plexiglass 

 stage for 4-pen arm design. 



FIG. 1 1 . Completed plexiglass stage with pen arm relays attached. 



FIG. 12. Sensor relay with wire (a) attached to the contact plate 

 and a slit (b) cut in the cover. 



