A sound card based multi-channel frequency measurement system

¹ Physics Department, Université de Fribourg, Chemin du Musée 3, 1700 Fribourg, Switzerland
² Paul Scherrer Institute, 5232 Villigen PSI, Switzerland

Corresponding author: Paul.Knowles@unifr.ch

Received: 7 July 2005
Revised: 24 October 2005
Accepted: 18 November 2005
Published online: 22 February 2006

Abstract

For physical processes which express themselves as a frequency, for example magnetic field measurements using optically-pumped alkali-vapor magnetometers, the precise extraction of the frequency from the noisy signal is a classical problem. We describe herein a frequency measurement system based on an inexpensive commercially available computer sound card coupled with a software single-tone estimator which reaches Cramér–Rao limited performance, a feature which commercial frequency counters often lack. Characterization of the system and examples of its successful application to magnetometry are presented.