PREPARATIONS FOR SOUNDING B2eai 
for poor contacts, loose connections, and electrical leakage, before the 
next raob. Place the Celsius psychrometer to the side of and about one 
inch from the thermistor. Make the psychrometric readings according 
to JB2-7, as supplemented below. 
a. Relative humidity of less than 10 percent may be encountered 
when taking a manual baseline-check. Enter the correct value 
on WBAN-31A, but set the relative humidity evaluator at 10 
percent for baseline-check relative humidity of 10 percentor 
less. 
14. Additional Preparation of Radiosonde. After the baseline- check 
psychrometric readings have been recorded and the recorder record 
baseline-check has been evaluated, open the door of the baseline- check 
box and disconnect the radiosonde test leads or plug from the test switch. 
Turn off the test switch and the blower, remove the radiosonde and close 
the door. 
14.1 Cutting Test Leads. Cut off the bare portion ofall test leads. Some 
observers may prefer to use a high (or low) reference to mark the re- 
lease, in this case approximately 1/32 inch of the high (or low) bare 
reference lead may be left on. If a second baseline-check is required 
after the test leads have been cut, strip not more than 1/4 inch of the 
insulation from each of the test leads. 
15. Pressure-Contact Setting. The pressure-contact setting is the 
position of the contact point on the commutator corresponding to station 
pressure corrected to the altitude of the radiosonde. Make the pressure- 
contact setting following the baseline-check. A contactonthe commutator 
extends from the left edge of one conducting segment to the right edge of 
the next insulating segment to the right. 
15.1 Baroswitch Setting Pressure. Determine the correct baroswitch 
pressure as follows: 
a. Obtain the station pressure from the precision aneroid barom- 
eter, altimeter setting indicator, microbarograph, or mercu- 
rial barometer (listed in order of priority). Apply any neces- 
sary correction established in accordance with WBAN Manual 
of Barometry. 
b. The station pressure must be corrected for the difference be- 
tween the elevation of the radiosonde atthe time the pressure 
setting is made and the Station Elevation. Use Table B2-2 to 
determine the correction corresponding to this difference. 
1-1-69 FMH#3 
