This Special Instruction is only for use on Cat products that use hydraulic cylinder position sensors.
This Special Instruction will guide the user thru the testing procedure for hydraulic cylinder position sensors.
ReferenceTool Operating Manual, NEHS0993, ” 276-7273 Cylinder Sensor Test Box (In Cylinder Function Test)”
ReferenceTool Operating Manual, NEHS0678, ” 146-4080 Digital Multimeter (Operation Manual) ”
Important Safety Information
Do not perform any procedure in this Special Instruction until you have read this Special Instruction and you understand this information. Use only proper tools and observe all precautions that pertain to the use of those tools. Failure to follow these procedures can result in personal injury. The following procedures should also be observed.
Work safely. Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs.
A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools in order to perform these functions properly.
Safety precautions and warnings are provided in this instruction and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard.
Therefore, the warnings in this publication and the warnings that are on the product are not all inclusive. Ensure that any tool, procedure, work method, or operating technique you use that is not recommended by Caterpillar is safe.
Ensure that the product will not be damaged or the product will not be made unsafe by the operation, lubrication, maintenance, or repair procedures used.
Use steps and handholds whenever you mount the machine. Use steps and handholds whenever you dismount the machine. Before you mount the machine, clean the step and the handholds. Inspect the step and handholds. Make all necessary repairs.
Face the machine whenever you mount the machine and whenever you dismount the machine. Maintain a three-point contact with the step and with handholds.
Note: Three-point contact can be both feet and one hand or a single foot and two hands.
Do not mount a moving machine. Do not dismount a moving machine. Never jump off the machine. Do not try to mount the machine when you carry tools or supplies. Do not try to dismount the machine when you are carrying tools or supplies. Use a hand line to pull equipment onto the platform. Do not use any controls as handholds when you enter the cab or when you exit the cab.
In addition to the normal safety precautions that are taken in the day to day operation of heavy machinery, the following steps are recommended:
- Move the machine to a suitable location. The location should be smooth, level, and out of direct sunlight.
- Move away from other working machines and personnel.
- Ground all implements.
- Stop the engine.
- Engage the machine brake. Put blocks in front of the wheels and behind the wheels.
- Install steering frame lock in the LOCKED position so the machine cannot articulate. (If used on the specific machine work is being performed on)Note: Turn the engine start switch key to the ON position but do not start the engine before performing step 7.
- Move the implement control levers through the full range of travel. This procedure will relieve any pressure that may be present in the implement hydraulic system.
- Depress the brake pedal repeatedly. This procedure will relieve any pressure that may be present in the brake hydraulic system.
- Turn the engine start switch key to the OFF position.
- Allow several minutes for steering system pressure to release.
- When possible, maintain ownership of the machine keys.
|Sensor Class Reference Table (1)|
|Part Number||Sensor Class||Part Number||Sensor Class|
|( 1 )||Table may not contain all the hydraulic cylinder position sensor part numbers available.|
|Digital Multimeter (Fluke Meter)
Digital Multimeter Gp
|1||276-7273||Sensor Test Box|
Test the Position Sensor using the 257-9140 Digital Multimeter and the 276-7273 Sensor Test Box
Use the following instructions in order to test the position sensors that are located on the inside of the cylinders.
- Plug the 276-7273 Sensor Test Box into the 257-9140 Digital Multimeter . The positive lead “+” from the sensor test box goes to the “red” terminal that is on the meter and the negative lead “-” of the sensor test box goes to the black terminal that is on the meter.
- Turn the 257-9140 Digital Multimeter to the “DC Voltage” setting (1) .
- Check the voltage of the battery that is inside of the 276-7273 Sensor Test Box . Press the button that is on the side of the test box (3) and hold the button on the side of the test box. The voltage of the battery that is inside of the test box should be 7 V to 10 V. If the battery voltage is not in this range, then replace the battery.
- After the voltage of the battery that is inside of the test box has been confirmed, release the button that is on the side of the test box.
- Disconnect the machine harness connector from the sensor on the cylinder. Plug the harness connector from the test box (4) into the connector on the sensor on the cylinder.
- Measure the signal voltage from the sensor. The value of the voltage should be in the range of 0.2 V to about 4 V.
- Press the “Hz” button (2) in order to cycle the 257-9140 Digital Multimeter so that the meter will read the pulse width modulated (PWM) frequency.
- Measure the PWM frequency of the sensor.Class 2 sensors … 115 Hz ± 15 Hz
Class 3 sensors … 500 Hz ± 100 Hz
Note: Refer to Table 1 in order to determine whether the sensor is a Class 2 or Class 3.
- Press the “Hz” button on the 257-9140 Digital Multimeter in order to read the percent of duty cycle.
- Measure the duty cycle of the sensor. Typically, the duty cycle will be between 1 percent and 95 percent.Note: For reference, both the signal voltage and the duty cycle should increase as the cylinder is extended.
Test the Position Sensor using the 146-4080 Digital Multimeter Gp and the 276-7273 Sensor Test Box
For instructions on using the 146-4080 Digital Multimeter Gp and the 276-7273 Sensor Test Box to test the hydraulic cylinder position sensors, refer to the following documents:
Tool Operating Manual, NEHS0993, ” 276-7273 Cylinder Sensor Test Box (In Cylinder Function Test)”
Tool Operating Manual, NEHS0678, ” 146-4080 Digital Multimeter (Operation Manual) ”
Tool Operating Manual, NEHS0682, ” 146-4080 Digital Multimeter Specification, Testing, and Maintenance Manual”