Figure 5-23.--E1ectrohydraulic signal flow between CRP components.
of the enclosure power supply and module circuit cards
Linear Potentiometer
in the following paragraphs.
The linear potentiometer provides the pitch
28V DC POWER SUPPLY.-- The power supply
feedback signal to the servo valve controller card in the
receives 115 volts ac, single phase power from the
CRP electronics enclosure. The resistance element is
propulsion local operating equipment (PLOE) console
about 10 kilohms from end to end. The term linear
through two 3-amp fuses. The incoming 115 volts ac is
means that the resistance is evenly distributed along the
reduced to 45 volts ac by a step-down transformer. This
potentiometer body. The voltage picked up by the
voltage is then rectified by the rectifier circuit board to
sliding contact is proportional to its position along the
provide a +25 and a -25 volt dc source. Three +25 volt
potentiometer body.
dc bus lines and three -25 volt dc bus lines carry power
throughout the enclosure.
Shaped Potentiometer
15V DC VOLTAGE REGULATOR.-- Two 15
The shaped potentiometer generates the pitch
volt dc voltage regulator circuit cards supply regulated
readout signal that is used to display pitch on the digital
power (.015 volt dc variance for either +15 volts dc or
demand display at the ECSS operating stations. The
-15 volts dc) to other circuit card modules. Several test
resistance across the shaped potentiometer from end to
point jacks and a failure alarm light are mounted on the
end is about 15 kilohms. The term shaped is used to
regulator card front panels. There are two output voltage
describe this potentiometer because the resistance is not
trimmer potentiometers mounted on the front panels of
evenly distributed along the potentiometer body. There
the regulator card.
is slightly more resistance at the ends than in the middle.
SERVO VALVE CONTROLLER CARD.-- This
This non-linear resistance distribution is necessary to
card provides the signal that operates the
counteract the increased sensitivity of the propeller pitch
when the valve rod is at the extreme ahead or astern pitch
electrohydraulic servo control valve on the OD box. The
settings.
pitch command signal from the ECSS comes into this
card and is summed with the feedback voltage from the
linear potentiometer. These two signals are compared
CRP Electronics Enclosure
and a correcting signal is sent to the servo valve if
necessary. The front panel of the servo valve controller
The CRP electronics enclosure is a rectangular case
card has three recessed potentiometers. Two of the
that contains six circuit cards. These cards are plugged
potentiometers provide separate gain adjustments for
into receptacles for easy removal and replacement from
ahead and astern pitch command signals. The third
the front. The CRP electronics enclosure front panel is
potentiometer feeds a small voltage to the command
shown in figure 5-24. A printed circuit board, containing
input and feedback summing junction to compensate for
a diode rectifier bridge, is bolted to the top of the
misalignment of the linear potentiometer. The servo
enclosure. Study figure 5-24 as you read the descriptions
5-24
