roswell

By knowing the altitude of release and counting the number of
switches from conductor to insulator, the position along the
the commutator is kno'Wtl. This in turn is calibrated to give
pressure values, from which the altitude may be computed.
This system was not suitable for floating balloons because
(1) only 70 to 90 discrete contacts are provided to cover the
entire atmospheric pressure range; this means that the best
readability obtainable with this system is about ~10 millibars.
(2) When the balloon oscillates about a floating level, the fre-
quent changes from one contact to another give ambiguous readings,
since the number of discrete resistances used is limited.
For circuit details of this unit, see T.E. Sig. 165 and the
Weather Equipment Technician's Manual.
(2) Specially Coded Radiosonde Modulators
To remove the ambiguity of altitudes reported by the system
above, extra resistances were introduced into the circuits
of those contacts near the floating level; thus, each contact
gives a distinctive frequency and each pressure (altitude)
can be clearly distinguished.
In this system, there still remains the lack of resolution or
sensitivity inherent in the modulator with 70 to 90 contacts.
(3) Olland-Cycle Modulator
To improve the sensitivity of the pressure measurements, an
Olland-Cycle (chronometric) pressure modulator ~s developed.
Seen in Figure 30, the modulator contains a standard Signal
Figure 30. Olland-Cycle pressure modulator.
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