bridge imbalance exists, the resulting dc voltage
basically the same manner. Bridge circuits
is ac modulated by the modulator circuit,
compare temperature selector and temperature
amplified by the cabin amplifier, and fed to the
sensor resistances, which represent selected and
control valve servomotor to either increase or
actual temperature conditions and generate a
decrease cabin temperature.
resultant dc error voltage. The dc error voltage
The function of the cabin duct limit bridge is
is then modulated and amplified. The resulting
to limit the temperature of the cabin inlet air. A
ac signal is the controller output, and it has phase
diode-biasing network permits the cabin duct limit
and voltage characteristics proportional to the
bridge to override the cabin temperature bridge
magnitude of the dc error signal. It goes to the
upon reaching the duct temperature limit. The
two-phase servomotor of the appropriate control
resulting dc voltage goes to the modulator circuit,
valve, where it modulates the valve to maintain
the cabin amplifier, and to the control valve
the selected temperature.
servomotor to decrease cabin temperature.
The cabin temperature channel (fig. 4-28) of
The cabin duct anticipator bridge functions
the temperature controller uses three bridge
with sudden changes of air temperature in the
circuits to maintain cabin temperature. Selection
cabin air inlet duct. To do this, the error voltage
of the desired temperature with the cabin
is capacitor coupled to the modulator. When the
temperature selector varies resistance of one
cabin temperature is being held at the selected
leg of the cabin temperature bridge. The varying
temperature with constant cabin inlet air tempera-
cabin temperature changes the resistance of the
tures, the anticipator bridge is in balance. Should
cabin sensor in the second leg of the bridge circuit.
duct temperature suddenly change, with all other
Thus, a selected temperature must have a change
of cabin temperature to provide bridge balance
conditions remaining the same, the anticipator
between the cabin sensor and selector. Whenever
bridge is unbalanced. This unbalance causes an
Figure 4-28.-Cabin temperature channel.
4-37
