Schweitzer Engineering Laboratories, Inc.

Travis L Mooney

Carl V Mattoon

Tony J Lee

Bruce A Hall

The present disclosure pertains correcting linear interpolation errors. In one embodiment, a system comprises an input configured to receive the periodic signal at a first sampling rate and an output configured to provide an interpolated representation of the periodic signal at a second sampling rate. A linear interpolation subsystem may establish a ratio between the first sampling rate and the second sampling rate to determine a slip frequency. The linear interpolation subsystem creates an interpolated representation of the periodic signal based on the ratio. The interpolated representation of the periodic signal includes a deterministic error attributable to interpolation. A linear interpolation correction subsystem may correct the deterministic error attributable to the linear interpolation subsystem and create a corrected interpolated representation. An application interface subsystem may provide the corrected interpolated representation to an application.

Correction for linear interpolation error

An RTD system includes multiple pluralities of RTDs and RTD bank assembly to which each plurality of RTDs are connected. Each RTD bank assembly includes a current source for the RTDs connected thereto, a multiplexer switching system for switching the current source successively between the RTDs, and a measurement function for measuring the voltage drop across the RTDs produced by the current source. The system includes a circuit for determining resistance of the RTD from the current applied thereto and the voltage drop there across. The system further includes a plurality of low pass filters associated, respectively, with each RTD, wherein the low pass filters are charged before the voltage measurement is made. The system includes a precharging arrangement where the low pass filter associated with the next RTD in a voltage sampling sequence is precharged, so that the delay between sampling of the voltage from the low pass filters associated with successive RTDs is significantly reduced. The system further includes low pass filters associated with calibration resistors which permit sampling of voltage values from the RTDs prior to the low pass filters associated therewith being fully charged, without error which would otherwise occur.

Resistive temperature device (RTD) module with improved noise immunity

The system includes a unipolar A/D converter, which samples analog signal inputs thereto, the A/D converter being used in a protective relay for electric power systems. The unipolar A/D converter is responsive to input voltage values and current values from the power line to produce corresponding digital signals. The A/D converter has a ground pin voltage reference at least as negative as the most negative point of the input signal to be processed.

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Pullman, WA, United States of America

Travis L Mooney