Evaluación de la resolución frecuencial en osciloscopios comerciales

Abstract

Digital and analogue oscilloscopes are necessary instruments in any teaching and research laboratory. Today's oscilloscopes can acquire signals and represent them in the time and frequency domains. User manuals describe well the time base and the storage capability, but they do not mention the important relationship between the number of data and the sampling frequency. These parameters are directly responsible of the frequency resolution that can be attained in a Fourier analysis. In this paper we compare various oscilloscopes with respect to the capacity they give the user to choose the number of data and the sampling frequency independently, and thus determine the frequency resolution, and avoid large unnecessary data files. The analysis was performed acquiring a mono chromatic signal with different oscilloscopes and different time basis. Results for a 10 Khz signal showed that when the auto button was used, there was up to a 50% error in the expected frequency, while only a 0.9% error was obtained with oscilloscopes that allow the user to choose independently the sampling frequency and the number of data.