High current precision resistance measurement system

A programmable resistance measurement system for generating a bi-polar current comprising:

• a bridge having
• a controller coupled a digital to analog converter and a first current tracking amplifier, the digital to analog converter for generating a first signal having a defined bi-polar current in response to a first received controller input,
• the first current tracking amplifier for generating a second signal having a defined bi-polar current in response to a second received controller input and a comparator input for receiving a third signal from a first comparator, and for transmitting a generated second signal to a reference resistor output;
• the first comparator for receiving the output of the first current tracking amplifier en route to the reference resistor, generating the third signal, and for controlling a switch to place the bridge into one of a first state and a second state, wherein
• in the first state a secondary input of the bridge is connected to ground such that the first signal from the digital to analog converter is coupled only to a first output of the bridge;
• and
• in the second state the first signal from the digital to analog converter is coupled to a second output of the bridge to provide the bi-polar current to a resistance being characterised;
• an extender having
• a bi-polar amplifier for receiving an output of a servo current tracking amplifier in a high current extender, for amplifying the received output, and for transmitting the amplified current signal as an output of the extender, 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 the output of the digital to analog converter, for amplifying the received input, and for transmitting the amplified signal as an output to a first high current extender output;
• and
• a high current comparator for receiving the outputs of the high current bi-polar amplifier and the bi-polar amplifier for controlling the servo current tracking amplifier to generate and transmit a signal having defined bi-polar current to the bi-polar amplifier in the extender.

A resistance measurement system for determining an unknown resistance in dependence upon at least a ratio of a test current and a reference current, each current established through setting a state of the resistance measurement system into each of a first state and a second state, the resistance measurement system for generating a bi-polar current, and comprising:

• a bridge having
• a controller coupled a digital to analog converter and a first current tracking amplifier, the digital to analog converter for generating a first signal having a defined bi-polar current in response to a first received controller input,
• the first current tracking amplifier for generating a second signal having a defined bi-polar current in response to a second received controller input and a comparator input for receiving a third signal from a first comparator, and for transmitting a generated second signal to a reference resistor output;
• the first comparator for receiving the output of the first current tracking amplifier en route to the reference resistor, generating the third signal, and for controlling a switch to place the bridge into one of a first state and a second state, wherein
• in the first state a secondary input of the bridge is connected to ground such that the first signal from the digital to analog converter is coupled only to a first output of the bridge;
• and
• in the second state the first signal from the digital to analog converter is coupled to a second output of the bridge;
• an extender having
• a bi-polar amplifier for coupling to the second output of the bridge, receiving the output of the digital to analog converter in the bridge, amplifying the received output, and for transmitting the amplified current signal as an output of the extender, 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 switching matrix having
• a first switch circuit for in a first configuration coupling the output of the digital to analog converter in the bridge to the bi-polar amplifier in the extender and in a second configuration coupling the output of the digital to analog converter in the bridge to high current bi-polar amplifier in the high current extender and the output of the servo current tracking amplifier in the high current extender to the input of the bi-polar amplifier in the extender;
• a second switch circuit for in the first configuration coupling the output of the bi-polar amplifier in the extender to the unknown resistance, in the second configuration coupling the output of the bi-polar amplifier in the extender to the high current comparator in the high current extender and the output of the high current extender to the unknown resistance, and in a third configuration coupling the output of the bridge to the unknown resistance.