214323 245 Revision A
3.8.18 Sensor Operation
Figure 3.439: Power, Ground, and Signal Wires
The position sensors supplied with auto header height
control (AHHC) system are 1000 ohm (1 k) industrial series
sensors containing sealed connectors. Normal operating
signal voltages for sensors fall between 10% (0.5VDC) and
90% (4.5VDC).
• A sensor operating with a signal voltage below 5% is
considered to be shorted
• A sensor with a signal voltage above 95% is considered
to be open
An increase in sensor voltage correlates to an increase in
header height.
Each sensor is constructed with a power wire and a ground
wire. Inside sensor, these two wires are connected by a
high resistance filament band (C). The resistance measured
across power (A) and ground (B) wires should read a
constant value between 800 and 1200 ohms (0.8–1.2 k)
with nominal reading being 1000 ohms (1 k).
Figure 3.440: Power, Ground, and Signal Wires
In addition to power (A) and ground (B) wires, a signal
wire (C) is connected internally to a movable wiper that is
attached to an external arm and sweeps high resistance
filament band. As external arm is rotated and wiper is
moved toward or away from power wire connection,
measured resistance at signal wire (C) changes.
The resistance measured across signal and ground wires
should increase uniformly from a low 80 – 100 ohms
(.08–0.1 k) to a high 800–1200 ohms (0.8–1.2 k). This can
be observed if an ohm meter is connected across signal
and power wires and sensor shaft rotated. When an input
voltage is applied to high resistance filament band through
power wire (A), output (or measured) voltage in signal
wire (C) is changed by this variable resistance.
NOTE:
Ground and power wires may differ depending on combine.
OPERATION
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