- Monitor display
- GPS receiver mast brackets
- Pitch/roll sensor
- Linkage position sensors such as rotary position sensor (boom and stick) and positioning sensing cylinder (bucket)
- Electronic Control Module (ECM)
- Laser catcher
- Left and right joystick switches (optional)
- Tilt bucket angle sensor (optional)
- Heading sensor (optional)
Front Linkage Position Sensors
The Grade Control system uses two rotary position sensors that are located on the boom and the stick. These sensors measure the relative rotation angle between the two linkages.
Rotary Position Sensor (Stick)
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| Illustration 1 | g02746578 |
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Rotary position sensor (stick) | |
The rotary position sensor that is mounted at the boom/stick pivot is used to measure the angle between the stick and the boom. The position sensor is an input to the ECM. The sensor continuously communicates the position of the stick to the ECM.
The position sensor for the stick is a pulse width modulated sensor. Pulse width modulated sensors have a duty cycle signal that varies as the condition changes. The sensor continuously generates a Pulse Width Modulation (PWM) signal. The frequency of this sensor signal is constant at approximately 500 Hz.
Refer to Systems Operation, Troubleshooting, Testing and Adjusting, "Connector Contact Description" for the connector information.
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| Illustration 2 | g02746962 |
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Rotary position sensor (boom) | |
The rotary position sensor that is mounted on the boom pivot is used to measure the angle between the boom and the body. The position sensor is an input to the ECM. The sensor continuously communicates the position of the boom to the ECM.
The position sensor for the boom is a pulse width modulated sensor. Pulse width modulated sensors have a duty cycle signal that varies as the condition changes. The sensor continuously generates a PWM signal. When the ECM receives the PWM signal, the ECM measures the duty cycle in order to determine the position of the boom. The frequency of this sensor signal is constant at approximately 500 Hz.
Refer to Systems Operation, Troubleshooting, Testing and Adjusting, "Connector Contact Description" for the connector information.
Refer to Special Instruction, M0069852, "Troubleshooting Guide for the Rotary Position Sensor for Cat® Grade Control on Certain Series E and Series F Excavators" for complete instruction on troubleshooting the Rotary Position Sensors (RPS).
Position Sensing Cylinder (PSC)
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| Illustration 3 | g02747122 |
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Example of a Position Sensing Cylinder (PSC) | |
The position sensing cylinder measures the rod extension and retraction of the hydraulic cylinder for the bucket. The PSC uses a sensor that is integrated into the cylinder to make this measurement. The sensor continuously generates a PWM signal. When the ECM receives the PWM signal, the ECM measures the pulse duration to determine the position of the bucket cylinder rod. The frequency of this sensor signal on the following models of excavators: 312, 316, 320, 324, and 329 is constant at approximately 500 Hz. The frequency of the sensor signal on the 336 and 349 excavators is constant at approximately 115Hz.
Refer to Systems Operation, Troubleshooting, Testing and Adjusting, "Connector Contact Description" for the connector information.
Refer to Special Instruction, M0064526, "Troubleshooting Procedure For Bucket Cylinder Position Sensing Unit on Certain Hydraulic Excavators Equipped With Cat® Grade Control".
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| Illustration 4 | g02747137 |
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Tilt bucket angle sensor | |
The Grade Control system supports an optional tilt bucket angle sensor to measure the cross-slope angle of the bucket. Data from the tilt bucket angle sensor is used by the system to provide continuously accurate guidance to the tip of the selected bucket tooth. The tilt bucket angle sensor is mounted to the tilt bucket or to a tilting quick coupler. The tilt bucket angle sensor communicates over the Controller Area Network (CAN).
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| Illustration 5 | g02747144 |
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Heading sensor | |
The Grade Control system supports an optional heading sensor to measure the heading of the linkage relative to a reference heading defined by the operator using the monitor display. The heading sensor measures changes in machine orientation relative to the magnetic field of the Earth as the machine is rotated. Combining heading measurements and body pitch/roll measurements allows the system to provide the operator with precise bucket guidance, even when the machine is rotated away from the original bench orientation while working on slopes. In addition, the usability and flexibility of the laser benching and touch point features are greatly enhanced.
The heading sensor is mounted on the counter weight of the machine, typically at the GPS mast mount furthest from the cab. The heading sensor communicates over the CAN.
Left and Right Joystick Switches
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| Illustration 6 | g02463138 |
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Left and right joystick switches | |
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| Illustration 7 | g02219234 |
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Left and right joystick switches | |
The Grade Control system supports the optional joystick handles with modulation and push-button switches. The modulation and push-button switches allow the operator to interact with the system to perform the following functions:
- Set and clear benchmark (push button)
- Adjust target depth and target slope (modulation switches)
- Perform touch point function or accept laser (push button)
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| Illustration 8 | g01894554 |
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Laser catcher | |
The laser catcher is a sensor that has a laser detection window that communicates laser strike information to the system when a laser signal is detected by the sensor. This information is used by the system to compensate for machine elevation changes as the machine settles or is relocated across the worksite. The laser catcher is mounted on the left side of the stick of the machine. The laser catcher communicates over the CAN.
Refer to Systems Operation, Troubleshooting, Testing and Adjusting, "Connector Contact Description" for the connector information.
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| Illustration 9 | g02747837 |
| (1) Location of sensor on frame | |
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| Illustration 10 | g02748105 |
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Sensor installed on frame | |
The Grade Control system utilizes a pitch/roll sensor to measure the front-to-back and side-to-side orientation of the machine chassis. These measurements are used by the ECM to calculate accurately the bucket tip position for guidance to the target elevation. The sensor is located on the upper frame next to the cab, below the boom pivot pin. The pitch/roll sensor communicates over the CAN.
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| Illustration 11 | g02378057 |
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Machine ECM | |
The sensors continuously communicate the position of the stick, boom, and the bucket to the ECM. The ECM uses the sensor inputs along with the machine and bucket dimensions to calculate the bucket tip position. Bucket tip elevation data and system status data is sent from the ECM to the display to provide guidance to the operator.
Refer to Systems Operation, Troubleshooting, Testing and Adjusting, "Connector Contact Description" for the connector information.
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| Illustration 12 | g02358256 |
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Monitor display | |
The monitor display provides a graphical user interface for the Grade Control system. The display shows information such as depth to grade, bench mark status, bucket profile view. With this information, the operator can operate the machine efficiently and achieve the desired grade. The monitor display also includes user interfaces to configure machine and work tool dimensions as well as other system options.
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| Illustration 13 | g03339395 |
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Rear GNSS counterweight mast mount location for earlier 312E, 316E, and 318E models | |
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| Illustration 14 | g03702238 |
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Right GNSS Forward Mast Mount Location (320E - 349E and F-Series Models) | |
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| Illustration 15 | g03702756 |
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Left GNSS Forward Mast Mount Location (320E - 349E and F-Series Models) | |
Note: GNSS Receiver mast bracket location can vary depending on model and vintage. Older E-Series 320 - E-Series 349 models that have not been reworked have rear counterweight GNSS Receiver mast brackets. Current and reworked E-Series 320 - E-Series 349 models have forward GNSS Receiver mast brackets.
Brackets fixed to the machine, provide a weld-free upgrade from Cat® Grade Control Depth and Slope to AccuGrade. Reference AccuGrade documents for further information on machines upgraded to AccuGrade.
Note: The factory installed brackets for the GNSS Receiver Mast have changed locations. Older E-Series machines have the brackets on the counterweight where as recent E-Series and F-Seriesmachines have the brackets in front of the engine cover.
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Satellite receivers (GPS) do not require daily maintenance for the operation of the system. The factory provided mounting locations for the satellite receivers are not intended to be accessed from locations on the machine. Accessing the satellite receivers from locations on the machine may result in serious personal injury or death. Use an approved external access system appropriate for the environment in order to access the factory provided mounting locations of the satellite receivers. |