This programme sets out to show how a simple friction measurement can involve the simultaneous analysis of the electrical signals from two pressure transducers and one accelerometer transducer.
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|David Crecraft; Gaby Smol; John Sparkes
|BBC Open University
|Accelerometer transducer; Amplitude difference; Phase difference; Spectrum; Synthesis; Wavelength
|Shots of pneumatic actuators at work in an automated production process. Shots of a working model, operated by two pneumatic actuators, which carries out simple 2 dimensioned automated tasks. Gaby Smol introduces the programme. Animated diagram of a pneumatic actuator. Commentary by Gaby Smol explains how it works. Shots of an experiment which measures seal friction in a pneumatic actuator at Bath University. Commentary by Gaby Smol explains what is happening. 2 pressure transducers and an accelerometer monitor the experiment. Shots of an animated diagram which shows details of the experiment. Shots of a friction/time graph for one stroke of the pneumatic actuator. Gaby Smol explains why measurements must be based on simultaneous signals from all 3 transducers. John Sparkes with a wave form synthesiser wired to a large display oscilloscope. Sparkes explains how the synthesiser works. He uses a diagram to aid. Sparkes synthesises a square wave approximation by the addition of sinusoidal waves. (Fourier synthesis). David Crecraft with a mechanical sine wave generator. He explains how the sine wave is generated. Crecraft with a mechanical square wave synthesiser. He explains how the synthesis is done and switches on the machine to demostrate. Sparkes with a diagram showing how a spectrum analyser is used to analyse complex wave forms (Fourier analysis). Sparkes demonstrates on the wave form synthesiser. He analyses a square wave form. Effect of phase on the Fourier synthesis and analysis of complex wave forms discussed. Sparkes shifts the phase of one of his sinusoidal waves (3rd harmonic). The spectrum analyser shows no change. Sparkes changes the phase of the 3rd harmonic. The wave is grossly distorted - the spectrum analyser shows no change. David Crecraft with the mechanical square wave synthesiser. He changes the phase of the 3rd harmonic and operates the machine. Here too a grossly distorted wave form results. Sparkes demonstrates and explains the effects of linear phase shift on the synthesised wave form. Gaby Smol with apparatus which displays signals from an accelerometer. Smol shows an accelerometer and explains how it works. He uses a diagram to aid. Smol demonstrates the apparatus with a damped and an undamped accelerometer. Signals are displayed using a swept frequency sine wave generator. A large display oscilloscope plots the amplitude and phase responses against frequency of the shaker. Effect of damping the transducer shows how the peak in response at the resonant frequency is removed at the expense of sensitivity. The optimum compromise for a "Linear" response is found.
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