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Sinusoidal waveform Where: Vis the instantaneous amplitude of the sine wave V m is the peak amplitude of the sine wave is the angular frequency (2 f)of the sine wave tis the time in second

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Sinusoidal waveform (cont.)

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Types of signal a: Static: DCb: Quasistatic c: Periodic: sine, square,..,v(t)=v(t+T) d: Repetitive: quasiperiodic e: Single event transient signal f: Repetitive single event

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Waveform symmetry A: Square wave with DC component that causes asymmetry B: Symmetrical square wave C: Sawtooth waveform forms mirror image across zero basline D: Quarter-wave symmetry A B C D

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Signal sampling Most instrumentation transducers have analog output At the interface between analog transducers and digital computers the signal must be digitized So the signal is sampled at regular intervals Each sample voltage is then converted into an equivalent digital value The next sample cannot be taken until the conversion of the last sample to digital form is completed

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Sampled signals A: continuous waveform B: Sampled version of continuous waveform C: Reconstructed waveform A B C

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Sampled signals A: Sine wave B: Sampling of sine wave C: Sampled sine wave A B C

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Effect of the sampling rate 1 Sample/sec 12 sample/sec If f sampling > f signal o.k. Ideally f sampling ≥ 2 f signal If f sampling < f signal aliasing Some applications don’t accept f sampling = 2 f signal as in ECG signal = 5 f signal

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Reconstruction of Sampled signals To reconstruct the original signal after sampling pass the sampled waveform through a low-pass filter that blocks f s Sampling is used to form AM, PM,

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