Sensors provide information to the Electronic Control Module ECM for the Payload system. This information is about changing conditions such as the oil pressure that is in the lift cylinder and the position of the lift arm. The ECM recognizes two types of signals from the sensors.
- Frequency signals. The sensor produces an AC signal. The frequency (Hz) varies as the condition changes.
- Pulse Width Modulated PWM. The sensor produces a digital signal. The duty cycle changes as the conditions change. The frequency of this signal is constant.
Frequency sensors produce a signal. The signal is a sine wave signal or a square wave signal. The frequency varies as the condition changes.
Oil Pressure Sensor for the Lift Cylinder
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| Illustration 1 | g00582059 |
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Oil Pressure sensor of the lift cylinder (1) Schematic Symbol. (2) Sensor. | |
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| Illustration 2 | g01358940 |
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Series H oil pressure sensor of the lift cylinder | |
The oil pressure sensor (2) reacts to the pressure that is in the lift cylinder. The sensor receives operating power from the electrical system of the machine. The sensor sends a square wave signal to the ECM. The signal varies in frequency as oil pressure that is in the lift cylinder changes. The ECM measures the frequency in order to determine the pressure that is in the lift cylinders. The sensor does not require calibration.
Pulse Width Modulated PWM Sensors
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| Illustration 3 | g00582060 |
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Pulse Width Modulated Signal | |
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| Illustration 4 | g00582064 |
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Typical PWM Sensor Schematic | |
Pulse width modulated PWM sensors produce a digital signal. The duty cycle of the signal varies as the conditions change. The frequency remains constant.
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| Illustration 5 | g00582067 |
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Lift Position Sensor (1) Schematic Symbol. (2) Sensor. | |
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| Illustration 6 | g00983934 |
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Lift Position Sensor (1) Schematic Symbol. (2) Sensor. | |
The lift position sensor is an input of the ECM. The position sensor is mounted at the pivot of the lift arm. The sensor is a Pulse Width Modulated PWM sensor. This operates on the voltage of the machine. The frequency (Hz) of this signal is 500 Hz. This frequency will remain constant. This sensor continuously generates a PWM signal. The duty cycle of the sensor varies in proportion to the angle of the lift arm. The control receives the PWM signal and the control measures the duty cycle. This determines the angle of the lift arm.
Note: The lift position sensor is the only sensor that must be calibrated.
Reference: Refer to Service Manual, SENR6614, "Position Sensor (Lift Linkage) - Adjust" for more information.