Electrical Description of EGM
Status September 2003 (EvoBus-Service / AFT)
Page: 47 of 83
3.2
Sensor technology
3.2.1
Active sensors
3.2.1.1
Internal control-unit sensors
A pressure sensor is used for comparative measurements of the respective atmospheric pressure (high
altitudes).
3.2.1.2
External control-unit sensors
Requirements for sensor inputs for external sensors:
Active sensors with an operating voltage of 5 volts are used. These sensors are capable of drawing a sink
current through a pull-up resistor toward their 5 volt supply. The sensors may use up to 15 mA of current
from the power supply. There are two sensor supplies. These are designed for the connection of up to
three sensors each (total current load is max. 45 mA).
The current limitation begins at currents greater than 60 mA.
Through the output voltage range (0.5 to 4.5 V) of the sensors used, the diagnosability with regard to
wiring breaks and short-circuits to earth is ensured. Active sensors are provided for the following input
variables.
Sensor data: (M447hLaG)
Measured Variable
Boost Pressure
Gas Pressure
(Woodward)
Active Oil Pressure
Absolute Pressure
Sensor
(Bosch Combi)
Air Mass
(not present)
RV in k
Ω
10 10 3.6 10
Pressure in kPa
15
284
100
1200
0
500
--
--
Voltage in V
0.22
4.50
0.79
3.98
6
4.5
--
--
3.2.2
Special sensors
3.2.2.1
Throttle-valve position sensors
In modern throttle devices the actuator, throttle valve and throttle valve sensor are integrated in one
housing. In the throttle device of the M 447 hLAG a potentiometer is used as a throttle valve sensor. This
is supplied by the internal electronics of the throttle device.
3.2.2.2
Lambda probe (Bosch LSU)
To control the air/fuel ratio on the inlet side, a Bosch model LSU broadband lambda probe can be
connected to the CNG control unit. Due to its constant characteristic curve in the area
λ
=0.7 to air, this
planar ZrO
2
two-cell limit current probe with an integrated heater is suitable both for
λ
=1 engines and for
lean engines. The lambda raw signal is processed with a specific evaluation IC of the probe manufacturer.
To compensate production-related sensor tolerances, a trimming resistor is integrated in the connector of
the lambda probe.
