Notes of the laboratory part

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MEASUREMENTS Asynchronous and synchronous sampling Time - averaging Giada Luppinoƒtel.: (02.2399) 8558 ƒe-mail: [email protected] Course website:ƒMeasurements on WeBeep Measurements 2021/2022 Sampling 1 Asynchronous sampling:the samples are recorded at constant time intervals. If we call 'tthe time elapsed between two subsequent samplings, the sampling frequency can be defined as fs=ଵ 'W. Synchronous sampling:the samples are acquired in a way that is synchronized with a given phenomenon. Generally speakingthe synchronous sampling is useful when exists a periodic phenomenon strictly related to the signal to acquire. Measurements 2021/2022 2 Sampling strategies AsynchronousSampling SynchronousSampling Measurements 2021/2022 3Synchronous Sampling Z '- gearwheel The time in which each sample of the signal is acquired is determined by the n impulses per revolution given by a fixed reference like an encoder. This results in an acquisition strategy at constant angle interval '-.In this way even if a change in the angular velocity appears, the number of samples acquired for each revolution remains the same. Measurements 2021/2022 Synchronous Sampling 4 With this sampling strategy it is possible to compensate possible variation of the angular velocity Z. %XWQRWDOOWKDWJOLWWHUVLVJROG« With the Synchronous Sampling strategywe face some questions:-How many points for each revolution should be recorded in order to sample the signal in a correct way?-What should I pay attention at? Measurements 2021/2022 Charachterizationof the behaviour of a single-cylinder engine alternator Problem: damaging of the rotor due to contact with the stator during bench and track tests. Problem sharpened during the transient. Possible causes: ‡Oscillationof the shaft (pitch) for some…