Frequency - The sensor produces an AC sine wave or a square wave at a frequency (Hz) that varies as the condition changes.
Analog - The sensor is a device with a reference voltage that is applied at the end terminals. The tap terminal is the terminal with the feedback signal. The resistance will change between the end terminal and the tap terminal, when the condition changes. The feedback signal is a smooth voltage that changes, which represents the status of the condition that is being measured.
Speed Sensor (Engine)
 | |
| Illustration 1 | g00020598 |
Speed Sensor (Engine) | |
The engine speed sensor is located on the flywheel housing. As gear teeth pass the end of the sensor, an AC signal is produced. The frequency of the signal is proportional to the speed of the gear teeth as the gear teeth pass the sensor. The controller makes decisions based on the speed sensor signal for the hydraulic pump and the engine control.
The quality of the installation of the sensor is extremely important. A sensor that is properly installed provides a signal that is of sufficient amplitude at all engine speeds. If the sensor signal is poor, the controller would interpret the poor signal as a low engine speed. The powershift pressure of the main pump may be drastically reduced.
See the Testing And Adjusting, "Speed Sensor (Engine) - Adjust" when the engine speed sensor is replaced.
Position Sensor (Governor Actuator)
 | |
| Illustration 2 | g00540911 |
Position Sensor (Governor Actuator) (1) Cylinder (2) Sensor Housing (3) Sensor Wiring | |
The Governor Actuator Control supplies power to the position sensor for the governor actuator at contact 1 and contact 19. The sensor works as a differential transformer and the sensor sends a feedback signal back to the governor actuator control at contact 13. The signal is a sine wave that has a frequency of 2.57 kHz. The amplitude of the sine wave is approximately 340 mV at high idle. The amplitude comes down to 0 mV as the cylinder moves toward medium idle. The phase of the sine wave changes at medium idle. Then, the amplitude increases back to 340 mV as the cylinder moves toward low idle.
The following figure shows the feedback signal from the position sensor back to the governor actuator control.
 | |
| Illustration 3 | g00588961 |
Feedback signals from the position sensor | |
The position sensor is incorporated in the governor actuator. The sensor sends a signal (voltage) that represents the position of the governor actuator to the governor actuator control. The governor actuator control then sends a signal to the controller. The feedback signal changes as the governor actuator moves.
The controller forces the governor actuator control to stop activating the governor actuator when the information for the position of the governor actuator matches the selection of the engine speed dial.
The position sensor for the governor actuator must be calibrated with the Portable Tech Station (with Electronic Technician) or the Portable Diagnostic Tool whenever the governor actuator is replaced. Calibrating allows the controller to know the feedback voltage that corresponds to the engine RPM that is desired. See the Testing And Adjusting, "Governor Actuator - Replace and Calibrate" for more information.
Potentiometer (Engine Speed Dial)
 | |
| Illustration 4 | g00544349 |
Potentiometer (Engine Speed Dial) | |
The engine speed dial provides the controller with information about the engine speed that is desired by the operator. The engine speed dial can be positioned anywhere between low idle and high idle. The Engine Speed Dial sends a voltage signal to the controller when the dial is positioned. This voltage is used by the controller to determine the desired engine RPM. The DC voltage at low idle is approximately 4.5 VDC (4.69 maximum). The DC voltage at high idle is approximately 0.5 VDC (0.3 minimum).
The resistance of the engine speed dial is 5 Kilo-ohms between contact "A" and contact "C". The potentiometer sweeps 318 degrees.
The engine speed dial must be calibrated after replacement. Calibration is used to determine the full voltage range of the actual potentiometer that is installed. See Testing And Adjusting, "Potentiometer (Engine Speed Dial) - Replace and Calibrate" for more information.