Copyright Goodheart-Willcox Co., Inc.
142 Hydraulic Systems for Mobile Equipment
A magnetostrictive cylinder sensor is an internal linear-displacement
transducer (LDT) that directly measures a cylinder’s position. The cylinder’s
piston and rod have a passageway drilled through their center. The sensor
has a shaft that fi ts inside the rod’s passageway. See Figure 6-26. A magnet is
located in the cylinder’s piston. As the piston is actuated, a pulse-width modu-
lated signal is transmitted through two wires located inside the sensor’s shaft.
The magnet moves in relation to the shaft, allowing the sensor to gauge how
far the cylinder has been extended. Magnetostrictive cylinders are used for
steering cylinders on combines and motor graders. The sensors are used for
automatic guidance systems.
Figure 6-25. A potentiometer is a three-wire variable resistor. The sensor provides a variable voltage input to an ECM.
Figure 6-26. This steering cylinder uses magnetostrictive sensing technology that provides an input to an ECM.
This technology is most common in machines with automatic guidance systems.
Sensor
signal voltage
+ 5 V
ECM
Wiper
Potentiometer
Sensor
shaft
Passageway
through
piston and rod
Sensor connector