349E, 349F and 352F Excavators and 349E MHPU Mobile Hydraulic Power Unit Tool Control System Caterpillar

Sensors provide information to the machine ECM about changing conditions. The sensor signal changes in a proportional manner. The sensor produces a digital signal (Pulse Width Modulation) that varies the duty cycle as the condition changes. The frequency of the signal will remain constant.

High Pressure Sensors

Illustration 1	g02263513

Table 1

Operating pressure	50 MPa
Supply Voltage	+7V ~ +14V
Output signal	500 ± 100 Hz (PWM)
Output range	5% ~ 95%

Note: The values in Table 1 are for bench testing only. Values may not represent parameters for machine systems specifications.

Tool Load Pressure

The tool load pressure sensor detects the signal of tool load pressure. The machine ECM will then control the pilot pressure using the proportional reducing valves for the attachment control valve in order to enhance synchronous operation.

The squeeze function utilizes the tool load pressure sensor to control pilot pressure to the attachment control valve spools.

Low Pressure Sensors

Illustration 2	g02263393

Table 2

Operating pressure	10 MPa
Supply Voltage	+7V ~ +14V
Output signal	500 ± 100 Hz (PWM)
Output range	5% ~ 95%

Note: The values in Table 2 are for bench testing only. Values may not represent parameters for machine systems specifications.

Hydraulic Foot Pedal

This pressure sensor is used to detect pedal operation for the tool. The signals from the sensor are sent to the machine ECM and are used for pump flow control and engine speed control.

Flow Limit Pressure

This sensor measures NFC pressure of each pump, and inputs the signal to the machine ECM. The pressure information is used for flow limitation control.

Boom UP Pressure

For tool systems in which the operation of combined flow from two pumps is available, this sensor detects boom UP signal. The signal changes the work tool pump operation from two pumps to one pump. This operation will enhance the synchronous operation of the work tool and the boom UP operation.

Boom DOWN Pressure

In tool systems in which boom down proportional reducing valve is installed, this sensor detects signal of boom DOWN operation amount. The signal is used to throttle the spool shift pressure of boom DOWN operation according to the intensity of this pressure. This operation will enhance boom down operability in time of heavy weight tool were installed.

Stick IN Pressure

For tool systems in which the proportional reducing valve for stick IN control is installed, this sensor detects signal of stick IN operation pilot pressure. The signal is used to throttle spool shift pressure of boom DOWN operation pilot pressure according to the intensity of this pressure. This operation will enhance stick IN operability in time of heavy weight tool were installed.

Stick OUT Pressure

For tool systems in which the operation of combined flow from two pumps is available, this sensor detects stick out signal. The signal changes the work tool pump operation from two pumps to one pump. This operation will enhance the synchronous operation of the work tool and the stick OUT operation.

Swing Pressure

For tool systems in which the operation of combined flow from two pumps available, this sensor detects a swing operation signal. This signal changes the work tool pump operation from two pumps to one pump. This operation will enhance the synchronous operation of the work tool and the swing operation.