Resistance ratio digitizing ohmmeter system

Details Resistance ratio digitizing ohmmeter system Resistance ratio digitizing ohmmeter system

2005-12-13

2005-12-13

Nguyen, Vinh (Department: 2829)

Electricity: measuring and testing

Measuring, testing, or sensing electricity, per se

Balancing

C324S523000, C324S600000, C324S607000

Reexamination Certificate

active

06975103

ABSTRACT:
A digitizing ohmmeter system for providing a digital resistance ratio measurement includes a high impedance current source providing a DC excitation current to an impedance-varying input sensor and a reference resistor and an ADC circuit including a charge-balancing modulator and a digital post processing circuit. The same DC excitation current passes through both the input sensor and the reference resistor. The system utilizes a switched capacitor input stage to sample the voltage across the input sensor and the voltage across the reference resistor to generate an input voltage step and a reference voltage step which are coupled to the modulator of the ADC circuit. The digitizing ohmmeter system thereby realizes fully ratiometric operation such that neither a precise current source nor a precise voltage source is required for accurate resistance ratio measurements and only a stable known reference resistor is necessary for accurate absolute resistance measurements.

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“Differential Input 16-Bit No Latency Delta-Sigma ADC,” Linear Technology LTC2433-1 Data Sheet, pp. 1-2 and 7.
“Thermistor-to-Digital Converter,” MAXIM, MAX6682 Data Sheet, (2 pages).

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