Pressure Output; Soft Start - GE Druck ADTS 405 Service Manual

Druck ADTS 405 Service Manual

Pressure output

19. The pressure generated in the manifold can be applied to the aircraft system by opening the
output solenoid. The command to open the output solenoid is received over the internal
communication ring. A signal is sent to the auxiliary drivers but the output solenoid will only open if the
ready line is active.
Ready line
20. The ready line must be in an active state to enable the auxiliary solenoid driver circuits. The ready
line is deactivated by an interruption of this line or by a fault detected by the watchdog timer and fail
safe circuitry. Under fault conditions the output valve instantly closes isolating the output from the
aircraft systems.
Soft start (Fig 1-7)
21. This provides an almost instantaneous transition from measure mode to control mode. When
the controller is off the switch is in the measure position, connecting amplifier A across the input and
output of the frequency compensation circuit. The output of the frequency compensation circuit is
forced to zero ensuring that no pulses will be applied to the pressure and vacuum valves when the
controller is switched on. When the controller is selected on, the set-point generator is adjusted until
the voltage at the output of the error amplifier is the same as the voltage applied to the frequency
compensation circuit by amplifier A. With equal voltage applied, the switch changes from measure to
control, disconnecting amplifier A and, amplifier B initiates the soft start signal to microcomputer which
switches on the controller. The value of the set-point is sent back to the microcomputer where it is
converted to current units of display and used as the current aim value. It takes less than 2 seconds for
the controller to come on-line.
K171 Issue No. 1
Figure 1-8 Pt Controller PCB Schematic
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