Speed of Light

# Here it is assumed that the cable is a lossless line

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Unformatted text preview: nstruction. Here it is assumed that the cable is a lossless line, where there is no heat dissipated in the line and the only “resistance” comes from the reactances of the inductance and capacitance of the wire, so that the characteristic impedance is Z0= L. C When a cable is connected to the source (where the signal comes from) or the load (what the signal is going into), it is important that the characteristic impedance matches their impedance otherwise signal reflection will occur. A terminator and cable with the same impedance rating should therefore yield minimal signal reflection at their junction. This is the concept behind impedance matching. The Oscilloscope If you've done the Faraday's Law lab before, you're familiar with the basic operation of an oscilloscope (in Faraday's Law, you used FFTscope, a virtual oscilloscope). Essentially, the amplitude of a quantity (usually Voltage) is plotted on the screen as a function of time, in real-time. It is possible to display one or two channels (quantities) at the same time; in the Faraday's Law lab you monitored Driving Voltage and Induced Voltage. Here we will monitor the detector pulse on Channel 1 (CH 1, yellow trace) and the laser pulse on Channel 2 (CH 2), blue trace. Procedure A. Effects of no termination, shorting, termination, and cable change Learn how to use a high-resolution oscilloscope. Send signal pulses from the colored box to the oscilloscope and see how the reflected pulse changes with cable used and method of termination. 1. Position the oscilloscope in front of you. If you wish you can gently flip out the front legs so that it is tilted upward for easier viewing. Make sure no cables are plugged into the front of the scope for now (Tconnectors are okay though). Press the ON button on the top left of the scope and wait 35-40 seconds for the grid to show on the display (ignore the Language selection...
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## This document was uploaded on 12/27/2012.

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