23 



NO TE: During all calibrating, make sure the tipping bucket 

 leg and magnetic bead are against the end of 

 adjusting screw "A". 



4. If the tipping bucket 'floats', turn adjusting screw "A" 

 clockwise (work in Va turns or less) while holding the locking 

 nut behind it. 



5. When the tipping bucket action is correct, carefully add 10 cc 

 of water to the tipping bucket. This much water should make 

 the bucket tip. Try for two trips, one each way, with a total of 

 20 cc of water. 



a. If more than 20 cc of water is required, turn adjusting 

 screw "A" counterclockwise. 



b. If less than 20 cc of water is required, turn adjusting screw 

 "A" clockwise while holding the locking nut. 



c. After each try, check for 'float'. 



6. After achieving two trips with 20 cc of water, turn adjusting 

 screws "B" until each side requires 10 cc of water. When this 

 is achieved and the bucket does not 'float' after tipping, the 

 instrument is calibrated to register each 0.25 mm of rain- 

 water, 



7. Make one final check to make sure the tipping bucket leg and 

 magnetic bead are against adjusting screw "A" and you can 

 hear a clicking sound when the bucket is tipping. 



NOTE: The collector should be washed periodically with a mild 

 detergent to insure that the collector surface is clean 

 and the orifice is clear of debris so that the rainwater 

 will run freely from the collector surface to the tipping 

 bucket. It is also advisable to clean the bucket occa- 

 sionally to insure accuracy of the measurements. 



CONSTRUCTING THE 3-PEN ARM DESIGN 



The constructions and wiring of the 3-pen arm and 4-pen arm 

 designs are similar in most respects. Refer to the construction of the 

 4-pen arm design for constructing, wiring, and calibrating the LWI 

 apparatus and the digital rain gauge apparatus. 



Constructing the Plexiglass Mount 



Materials 



(1) plexiglass sheet, 4.5 cm wide, 15 cm long, and 6 mm thick 



(2) bolts, 2 cm long 



(1) SPDT momentary spring-return switch 



Instructions (refer to Fig. 19) 



A) Measure 5 cm firom one end of the plexiglass sheet and draw 

 a line perpendicular to the end. 



