Patent ID: 8106669

Claim:
A resistance measurement system for generating a bi-polar current comprising: a bridge having a controller, a digital to analog converter for generating a first signal having a defined bi-polar current, a first current tracking amplifier for generating a second signal having a defined bi-polar current, and for transmitting the generated second signal to a reference resistor, a first comparator for receiving the output of the first current tracking amplifier en route to the reference resistor and for controlling a switch to place the bridge into a first state and a second state, the first state connecting a secondary input of the bridge to ground and the second state connecting the output of the digital to analog converter to a test resistance; an extender having a bi-polar amplifier for receiving the output of the digital to analog converter in the bridge, for amplifying the received converter output, and for transmitting the amplified current signal as an output, and a second comparator for receiving the output of the bipolar amplifier, for controlling a second current tracking amplifier to generate and transmit a signal having a defined bi-polar current to the secondary input of the bridge, and for receiving the output of the second current tracking amplifier en route to the secondary input of the bridge; and a high current extender having a high current bi-polar amplifier for receiving as an input, the output of the digital to analog converter, for amplifying the received input, and for transmitting the amplified signal to the test resistance; and a high current comparator for receiving the outputs of the high current bi-polar amplifier and the bi-polar amplifier for controlling a servo current tracking amplifier to generate and transmit a signal having defined bi-polar current to the input of the bi-polar amplifier in the extender.