Lab 1 - Oscilloscope

Lab 1 - Oscilloscope - PHY134 - Classical Physics I...

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PHY134 - Classical Physics I Laboratory The Oscilloscope The aim of this experiment is to familiarize you with the use of a cathode-ray oscilloscope. This instrument will be employed in some of the later experiments, as well as in many electronics and research laboratory, so it is important to clearly understand its principles and its operation. The Oscilloscope The oscilloscope is somewhat similar to a traditional TV, where you have an electron beam in an evacuated tube hit a phosphor-coated glass screen to make light where it hits. (To borrow from the author Edward Abbey, the use of a vacuum tube explains why watching TV tends to suck your brains out). The electron beam is deflected up/down and left/right by voltage applied to some plates in a manner like Example 21.8 on p. 811 of your textbook. External voltages can be input to the y -axis or vertical amplifiers (typically on the left side of the scope) which control the vertical motion of the electron beam and thereby the vertical position of the spot on the phosphor-coated screen. The voltage on the x -axis amplifiers, controlling the horizontal motion ("time base") of the cathode beam, is generated internally. The internal horizontal voltage has a saw-tooth shape, moving the spot with constant speed from left to right, and then back almost instantaneously. The horizontal speed (i.e. the frequency of the saw-tooth) can be controlled by the "time-base" unit on the right. Because the time base voltage has a calibrated "sweep" time, the displayed signal can be read off as voltage (vertical) versus time (horizontal). The vertical signal can be amplified (calibrated amplification factors) and displaced vertically ("offset") over the screen. The intensity and focus of the spot on the display can be varied. The vertical input can be put to ground (GND or 0 V), or coupled to the input signal connector directly (DC; direct current) or via a capacitor (AC; alternating current) which prevent any constant voltage level to pass, and only the time-varying part of the signal to pass (so that for
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This note was uploaded on 09/26/2008 for the course PHY 132 taught by Professor Rijssenbeek during the Spring '04 term at SUNY Stony Brook.

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Lab 1 - Oscilloscope - PHY134 - Classical Physics I...

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