Fluke Corporation

Fluke Precision Measurement Limited

Other

Hong Yao

Yong Yang

Fei Yang

Chao B Zhang

Chao Zhang

Hua Qui

An amplifying circuit comprises a differential input stage having a first input terminal, a second input terminal, and an intermediate node, wherein the differential input stage is configured to generate a differential current flowing through the intermediate node in response to an input voltage difference between the first and second input terminals. The amplifying circuit further comprises a first current source coupled to the intermediate node, which is configured to provide a first bias current which allows the differential current to vary within a predetermined range. The amplifying circuit further comprises an output terminal coupled to the intermediate node, and a second current source coupled to the intermediate node and configured to provide a second bias current. The second bias current compensates the differential current and the first bias current and produces an output current flowing through the output terminal in a predetermined direction. A measurement device is also described.

Differential amplifier design as the preamp of DMM

A current sensing circuit comprises a first input terminal and a second input terminal for introducing a subject current from a device coupled between the first and second input terminals; a first amplifier having a first input node coupled to the first input terminal via a protection resistor, a second input node coupled to the second input terminal, and a first output node coupled to the first input node via a capacitor, wherein the first amplifier has a current sensing path for sensing the subject current and converting the subject current into an output voltage that changes with the subject current; and a protection circuit coupled between the first and second input nodes of the first amplifier, wherein the protection circuit is configured to draw a protection current from the first input terminal through the protection resistor to at least partially offset the subject current.

Current sensing circuit

The current sensing circuit includes a first input terminal and a second input terminal for introducing a subject current that flows in a current path; a shunt resistor coupled in the current path for converting the subject current into an output voltage difference across the shunt resistor; an amplifier having a first input node coupled to the first input terminal, a second input node coupled to the second input terminal, an output node, and a feedback path including an over-current protection device, wherein the feedback path is coupled between the output node and the first input terminal; and an output terminal coupled to the second input terminal and the shunt resistor to output the output voltage difference. The current sensing circuit has a relatively large current measuring range and a small burden voltage. A measurement device is also described.

Active current measurement circuit and measurement device

An amplifier circuit is used in a multimeter to amplify signals applied between a pair of test terminals. A voltage applied to one of the test terminals is amplified by a first operational amplifier configured as a voltage follower. An output of the first operational amplifier is applied to an inverting input of a second operational amplifier configured as an integrator. An output of the second operational amplifier is connected to the other of the test terminals. A voltage generated at the output of the second operational amplifier provides an indication of the magnitude and polarity of the voltage applied to the first and second test terminals.

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Shanghai, China

Hong Yao