TB 9-6685-322-50
NOTE
This procedure is to be used for the initial calibration of all
thermometers listed In table 4. Thereafter, the thermometer
will be checked at the lee point only. Changes in the correction
at the ice point will be applied to all corrections. That is, if the
lee point correction Increases, then the Increase will be added
to all corrections. If the ice point correction decreases, then the
decrease will be subtracted from all corrections. If the shift In
the ice point exceeds the rejection tolerance specified in table 4,
the thermometer will be replaced. Thermometers which do not
have ice points will be tested at some other point. Testing at
some temperature other than the Ice point requires a
controlled temperature calibration bath and a temperature
standard.
7. Equipment Setup
a. Remove TI from protective case.
NOTE
thermometers.
c. Hold TI in vertical position and observe that bulb and column are free from gas
bubbles and stem is free from globules of liquid. If not, perform (1), (2), or (3) below as
applicable.
(1) Eliminate gas bubbles in TI bulb by cooling with dry ice or equivalent coolant
until liquid is drawn into bulb. Tap TI gently against pad of paper or against palm of hand.
Bubbles should rise to surface and disperse.
(2) Eliminate gas bubbles from stem of TI by slowly and carefully heating bulb until
bubbles are joined. Carefully tap TI against pad of paper or against palm of hand.
CAUTION
To avoid damage to TI, exercise extreme care when applying
heat.
(3) Eliminate globules of liquid inside TI stem by carefully and slowly heating TI
bulb until liquid column merges with globules.
NOTE
If globules tend to unite and reappear after bulb cools,
obstructions or oxidation of mercury may be -present and TI
must be rejected.
4