Class: BE-309
Group: M1
Members: Rob Jenkins, Rob Ledger, Minhthe Luu, Dan Pincus
Date: December 10, 1998
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Abstract:
This experiment accomplished two goals: construction of Twin Tee and Wien Bridge 60Hz notch filters and evaluation of their response to frequency sweeps and EKG signals. Bode plots show a maximum attenuation of 35dB at 62.4Hz for the Twin Tee and 42.7dB attenuation at 55.6Hz for the Wien Bridge when fed a 10VP-P frequency sweep. The data show that the Wien Bridge had comparable performance to the Twin Tee in attenuation of 60Hz noise from an EKG signal + 10% 60Hz noise, with 17.5dB and 18.1dB attenuations respectively. A noise to signal attenuation ratio demonstrates that the Wien Bridge and Twin Tee were comparable for an EKG + 10% 60Hz noise with a ratio of 4.7 and 4.66 respectively, but the Twin Tee outperformed the Wien circuit for an EKG + 100% 60Hz noise signal with 3.75 and 2.80 ratios respectively. A 2nd order digital Butterworth filter consistently attenuated 60Hz noise more than 1st order for both 10% and 100% 60Hz noise content in EKG signals.