Chapter 4 — TEMPERATURE, HUMIDITY, AND PRECIPITATION 



1. Sliding door. 



2. Spring contact. 



3. Battery com- 

 partment. 



4. Water bottle. 



5. Bottle com- 

 partment. 



6. Hinge pin. 



7. Thermometer 



holder. 



Wet -bulb wick. 

 9. Knob. 



10. Exhaust 

 ports. 



11. Sliding air 

 intake. 



Figure 4-6. — Rotor psychrometer. 



209.90 



209.116 

 Figure 4-7. — Hand electric psychrometer ML- 

 450A/UM. 



corrosion or pitting. No lubrication is necessary 

 for this instrument; no special tools are re- 

 quired for its overhaul. 



BATTERIES. — Three size D (standard flash- 

 light) dry cell batteries are required. To insert 

 the batteries, remove the sliding door at the 

 end of the case and rotate the spring contact 

 from the battery compartment to the bottle 

 compartment. 



The batteries must be inserted so that the 

 center contact enters the compartment first. 

 After the batteries are in place, rotate the 

 spring contact to its original position on the 

 end battery and replace the sliding door. 



REPLACING THE WICK. — To replace the 

 wick, first remove the sliding air intake ex- 

 posing the thermometer bulbs. Then remove the 



wick. Slip a length of wicking over the bulb. 

 Secure at the top of the bulb with a thread at 

 the constriction between the bulb and the stem, 

 using a loop and square knot. Form a loop 

 in a second thread and place it at about the 

 middle of the bulb, stretching the wick firmly 

 and snugly against the bulb. Tie with a double 

 loop and square knot at the end of the bulb. 

 Clip the ends of the thread and cut off the 

 excess wicking about one-eighth inch below the 

 bottom of the bulb. 



REMOVING AND REPLACING THERMOM- 

 ETERS. — If either thermometer is damaged, 

 it is necessary to remove both thermometers 

 and replace them with a matched pair. To 

 remove and replace the thermometers, first 

 remove the air intake and the thermometer 



59 



