This programme is about two techniques for improving the signal to noise ratio of a 'noisy' signal, namely filtering and averaging. Instrumentation systems often require analogue signals to be tran...smitted and processed in a digital form and this is often done by sampling. This technique is demonstrated using a sine wave signal and a sampling circuit driven by a pulse generator.
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|David Crecraft; Glyn Martin; John Monk
|BBC Open University
|Averaging; Filtering; Periodic signals; Real-time spectrum; Sampling
|David Crecraft introduces the programme. He sums up the experiments with wave synthesis which were examined in the previous programme and explains that this programme will deal with the elimination of" unwanted signals from a wave form. Crecraft explains and demonstrates the "filter" technique of eliminating unwanted wave form components. He uses a wave form synthesiser and electronic filters in his demonstration. Crecraft shows an animated diagram (graph) which gives details of low pass filter characteristics. Frequency response is plotted. Spectrum analyser shows frequency components being removed by the filter. Crecraft explains and demonstrates the removal of noise from a wave signal. He demonstrates with signals outside the noise band and within the noise band. Animated graph gives details of high pass filter characteristics (band pass filter). Crecraft demonstrates. John Monk plays the recorder in the lab. Spectrum analyser signal/superimposed. Glyn Martin introduces electronic-noise to the recorder signal and then eliminates the noise by filtering. He explains how this was done. Shots of filter box controls. Martin then demonstrates and explains how to remove a narrow band noise signal from a wide band signal. The wide band signal is provided by a record player and the noise by the studio cooling fans. Martin uses a 'band stop filter' in this case. Crecraft introduces excerpt from SDT 286/02. Ivor Gartside recovers signals from noise with an averager. Excerpt from SDT 286/02. An electric shock stimulus is applied through electrodes to Stephen Rose and the response/s monitored on an oscilloscope. Gartside uses averaging technique of noise removal to obtain a clear response signal. A regular wave form is built up on the oscilloscope screen. John Monk explains and demonstrates the averaging technique of noise removal. Monk uses a graph to aid his explanation. David Crecraft introduces the 'sampling' technique of noise removal. Glyn Martin demonstrates the sampling technique of noise removal. He briefly explains the apparatus and points out its components. Martin continues his demonstration and explanation. David Crecraft sums up.
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