SELECTION OF PFM SIGNAL PERIOD FOR T/D CONVERSION

D. Swisulski

Abstract

This paper presents principles of selecting the period of pulse-frequency modulated (PFM) signals used as intermediate representation of measured signals. It is assumed that the PFM signal is to be digitized using time-to-digital (T/D) conversion, and that the measured signal can be modeled as a dc component plus a sinusoidal fluctuation of known frequency. The measurement error, mainly composed of dynamic error and counting error, can significantly be reduced by properly selecting the period of the PFM signal with respect to other measurement conditions. Included are considerations pertaining to both on-line and off-line postprocessing of the T/D conversion readouts. In the case of speed measurement by means of incremental encoder, the proposed method of period selection indicates the most favorable number of encoder pulses per shaft revolution.

Keywords

PFM signals, period counting, dynamic error

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IMEKO-WC-2000-TC4-P159.pdf

DOI

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IMEKO TC

TC4 - Measurement of Electrical Quantities

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