Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2005-06-07
2005-06-07
Pert, Evan (Department: 2829)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
Reexamination Certificate
active
06903558
ABSTRACT:
A digitizing ohmmeter system for providing a digital resistance measurement includes a current source for providing an excitation current to an impedance-varying input sensor and an ADC circuit including a charge-balancing modulator and a digital post processing circuit. The system utilizes synchronous AC excitation of the input sensor and an AC coupled analog-to-digital converter input. The digitizing ohmmeter system also implements correlated double sampling for noise cancellation to provide low noise and highly accurate analog-to-digital conversions. The ADC circuit includes a reference signal generator generating a resistance reference signal by time-sharing the excitation current with the input sensor. 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 measurements.
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Maxim MAX6682 Thermistor-to-Digital Converter data sheet, 19-2219; Rev. 0: 2/02, pp. 1-8.
Blom Eric D.
Holloway Peter R.
Urie Stuart H.
Wan Jun
Cook Carmen C.
National Semiconductor Corporation
Nguyen Trung Q.
Patent Law Group LLP
Pert Evan
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