Chapter 4 -TEMPERATURE, HUMIDITY, AND PRECIPITATION 



REUNITING MERCURY COLUMN. — If the 

 mercury column of either thermometer sep- 

 arates, an effort should be made to reunite 

 the mercury column. To do this, remove the 

 thermometer as described earlier. Gently heat 

 the thermometer bulb under a light bulb to 

 gradually force the mercury to the top of the 

 tube. Care must be taken so the mercury does 

 not cause the thermometer to burst. Upon 

 cooling, the mercury should recede as a united 

 column. 



REPLACING THE LAMP. — To replace a 

 lamp, first remove the sliding air intake and 

 retaining screw that keeps the thermometer 

 holder in the correct position. Then raise the 

 unrestrained end of the thermometer holder 

 upward to provide access to the lamp. Finally, 

 remove the red filter and change lamps, re- 

 place the filter, and secure the thermomster 

 holder; replace the air intake. 



INSPECTIONS. — Inspect for cracks or breaks 

 in the plastic parts. Inspect threaded holes and 

 screws for wear, and the fan for damage. In- 

 spect the thermometers for cracks and sepa- 

 rated mercury columns. Inspect the carrying 

 case for damage, and the motor shaft for 

 smoothness of rotation. 



REPAIR OR REPLACEMENT. — All plastic 

 parts that are broken, cracked, or have missing 

 or damaged threaded inserts should be replaced. 

 Damaged screws should be replaced. If the 

 motor shaft does not turn freely or if the fan 

 is damaged, the motor and fan assembly should 

 be replaced. If the contacts on the contact 

 block do not contact the motor terminals cor- 

 rectly, they should be carefully bent so that 

 good electrical contact is ensured. A carrying 

 case that is damaged beyond use should be 

 replaced. 



SEMIAUTOMATIC AND AUTOMATIC 

 WEATHER STATIONS 



The AN/GMQ-29( ) is scheduled to com- 

 pletely replace the AN/GMQ-14( ). Because of 

 the lengthy installation period, both the AN/ 

 GMQ-14( ) and the AN/GMQ-29( ) are discussed 

 in this manual. 



AN/GMQ-14( ) 



Semiautomatic Meteorological Station AN/ 

 GMQ-14( ) is an electromechanical instrument 

 system with facilities to house, sense, and re- 

 cord temperature, dew point, precipitation, pres- 

 sure, and wind. (See fig. 4-9.) Barometer 

 ML-448/UM and the Marine Barograph are 

 covered in chapter 2 of this training manual. 

 Wind Recorder RD-108( )/UMQ-5 is covered 

 in chapter 3, along with the AN/UMQ-5( ) 

 wind system. 



This station includes a rain gage; a DEWCEL 

 (dew point sensing element) housed in a shelter; 

 a dewcel power supply; a dew point transmitter; 

 an air temperature bulb; and air temperature 

 transmitter; an equipment rack containing a 

 combined rainfall, dew point, and temperature 

 recorder; a 24-hour clock; a junction box; and 

 a test cord. 



Three systems in the semiautomatic mete- 

 orological station are covered in this chapter. 

 They are the dew-point measuring and record- 

 ing system, the air temperature measuring and 

 recording system, and the rainfall gaging and 

 recording system discussed under rain gages. 



Dew-point Measuring and 

 Recording System 



The dewcel, covered with woven glass tape 

 impregnated with lithium chloride and wrapped 

 with gold or silver wires, measures the dew- 

 point temperature. 



The current for the dewcel passes through 

 the dewcel power supply, consisting of a step- 

 down transformer and an incandescent lamp 

 used as a ballast resistor. The dewcel actuates 

 the temperature element in the transmitter as- 

 sembly. 



Air Temperature Measuring 

 and Recording System 



The temperature measuring and recording 

 system operates similarly to the dew-point 

 measuring and recording system. Instead of 

 the dewcel, a temperature bulb is used and 

 no separate power supply is required. The 

 temperature bulb is similar to the dewcel minus 

 the glass tape and wire wrappings. The sig- 

 nal is recorded by the center pen on the right 

 half of the chart. 



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