PREPARATIONS FOR SOUNDING Baa 
voltage prong is accidentally pushed part way in a high voltage socket. 
If a filament switch is provided, it shouldbe in the "off" position before 
the battery plug is inserted into the socket; if a twisted wire type fila- 
ment switch is provided, these black wires should be separated. The 
radiosonde should be kept in an upright position once the battery is in- 
stalled. 
2.4.1 Battery Time. If the battery is used for the baseline-check, the 
filament circuit should normally be left closed after the radiosonde is 
placed in the baseline-check box. The exposure time in the baseline- 
check box should be kept to a minimum, The workload should be so 
arranged that the release can be made within a few minutes after the 
completion of the baseline-check. This will reduce the battery drain to 
a minimum. The drain on the battery from the time it is connected after 
activation until the time of release should notexceed 25 minutes. If this 
limit is expected to be exceeded, the battery should be disconnected. If a 
filament switch is provided, open the filament switch. The battery may 
be left disconnected for up to 15 minutes. If the battery has been dis- 
connected more than 15 minutes, it will be checked to see if it still meets 
the minimum voltage requirements. When the battery is reconnected, 
allow a minimum of two minutes for the battery voltage to stabilize. On 
radiosondes equipped with twisted lead type of filament switch be sure 
that the leads are very tightly twisted. 
2.5 Thermistor. (WB, AF). Normally the thermistor is factory in- 
stalled. If not already installed or if a replacement is needed for any 
reason, the thermistor leads will be soldered to the leads on the out- 
rigger of the radiosonde prior to the baseline-check. The thermistor 
should always be handled by its leads to avoid touching the white coating. 
A heat sink shall be placed on the thermistor leads when soldering to 
avoid damaging the temperature element. An alligator clip, attached to 
the lead between the thermistor and the end to be soldered, provides an 
acceptable heat sink. Use only thermistors which have clean, unbroken 
white coatings. Thermistors with chipped or soiled coatings should be 
replaced at some convenient time before the radiosonde is to be used. 
2.5.1 Thermistor. (N). The thermistor will be installed in accordance 
with instructions for the type of radiosonde in use. 
2.6 Installation of Hygristor. The hygristor element is packed ina 
closed air-tight container for shipment. If a humidity indicator is also 
enclosed with the hygristor, it will be inspected upon opening the con- 
tainer. The indicator should show blue; if it shows white or pinkish- 
white, reject the hygristor. The container should not be opened until just 
before preparation of the radiosonde for the baseline-check. Once the 
i= 126g FMH#3 
