Doosan 10/105CWJD, Electronic Service Manual

Page: 9 / 139

Book: 23227143 (8-24-2010) Rev C
Page 7
Sensors and Transducers
The electronics system contains sensors and transducers that are used to collect
data from the compressor. The temperature is measured by thermistor and RTD
type temperature sensors. These devices exhibit a change in resistance as the
temperature changes. The resistance causes an input voltage change to the
WEDGE controller input and is interpreted as a temperature change.
The electronics system also uses pressure transducers to measure compressor
pressure changes. These devices have an output signal of 0.5 VDC to 4.5 VDC,
corresponding to 0 psi and the maximum measured psi for a particular device.
The devices are gauge pressure devices. These transducers are provided with 5
VDC excitation to power the device. These are three WJDe devices: excitation,
signal and ground.
Digital Inputs and Outputs
The WEDGE controller scans digital inputs such as switch contacts. These are
either 24 VDC or (0 VDC). These digital inputs are connected to switches within
the package.
The WEDGE controller provides 24 VDC digital outputs to control solenoids,
relays, and other devices. These are 24 VDC "ON" and 0 VDC "OFF". They are
current limited and short circuit protected.
Controller Outputs
The WEDGE controller has three types of outputs: frequency, pulse width
modulated (PWM) and 24 VDC digital (ON /OFF).
Pressure Control
The discharge pressure is controlled by manipulating the engine speed and
compressor inlet valve position. The inlet valve position is controlled
pneumatically and the engine speed is determined by the WEDGE controller.
The WEDGE measures the pneumatic system regulation pressure and computes
an engine throttle setting. This throttle setting is sent to the engine via the
frequency, PWM, Analog, or J1939 throttle, depending on which technique is
used. The engine controller will control engine speed to this throttle setting.