Caterpillar Inc.

Brian W Mann

James A Antone

David R Meinhold

Jim B Maddock

A calibration apparatus and method for calibrating a hydraulic control valve connected to an electronic controller. The electronic controller selects control signals and reads corresponding hydraulic pressure outputs of the hydraulic control valve and selectively records values corresponding to control signals that produce desired calibration pressures.

Automatic solenoid control valve calibration

The present invention is directed toward a circuit for receiving an input current and for producing an output voltage proportional to the input current. The circuit includes a first transistor which receives the input current, and a second transistor connected to the first transistor, wherein the first and second transistors comprise a current mirror topology. A third transistor is connected in series with the first transistor, and an operational amplifier has an output which is connected to the base of the third transistor. The third transistor has a collector coupled to a base junction of the current mirror. The operational amplifier has a positive input terminal coupled to a collector of the second transistor through a first resistor, and a negative input terminal coupled to an emitter of the third transistor through a second resistor, the first and second resistors having substantially similar impedance values.

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Edwards, IL, United States of America

Brian W Mann