Core Practical 5.3: Using a CRO FF! Wednesday, 27 February 2019 1

Learning Objectives To use timebase and y-gain settings to determine the time period, frequency and amplitude of a number of signals FF! Wednesday, 27 February 2019 2

By the end of the lesson FF! Use a variety CRO settings to determine the amplitude of a signal. Show clearly the steps and processes gone through to determine the time period and frequency of a number of signals. Investigate whether a change in frequency has an effect on the amplitude of a signal. Grade E Grade C Grade A FF! Wednesday, 27 February 2019 3

Use your phone to watch it individually if you’d rather. CR What is a CRO? How does it actually work? Use your phone to watch it individually if you’d rather. FF! Wednesday, 27 February 2019 5

Look at these traces…. FF! B C These are all traces obtained when the timebase was turned off. Using what you know, can you suggest the type of supply for each? Be as detailed as you can. Does this help? A 4 3 5 D E F 6 1 2 1. d.c input upper plate positive 2. d.c input upper plate more positive 3. no input – spot adjusted left 4. no input 5. d.c input lower plate positive 6. a.c input FF! Wednesday, 27 February 2019 6

Now look at these descriptions. d.c input – upper plate positive no input low frequency a.c input high frequency a.c. input d.c input – lower plate positive a.c input with a diode Sketch what you think each of these would look like. A F F E C B D E B A C D FF! Wednesday, 27 February 2019 7

Link to video in case you need it again! CR Link to video in case you need it again! FF! Wednesday, 27 February 2019 8

Link to video in case you need it again! CR Determining Amplitude and Frequency from a CRO Display Sketch and oscilloscope trace and annotate it to show what is meant by timebase and y-gain and then describe and explain how they can be used to find the value for amplitude and frequency of a signal. Don’t for get to refer to units correctly throughout your explanation. Link to video in case you need it again! FF! Wednesday, 27 February 2019 9

Procedure One of you choose a setting on the signal generator for frequency and amplitude and then choose timebase and y-gain settings. Now turn the CRO around (or cover that part of the screen) so the person who didn’t set it can see the trace but not the signal generator or settings. Draw out and then calculate SHOWING ALL WORKING the amplitude and frequency of the trace. Get the person who set it up to check your answers. Exchange places and repeat the process. Each of you needs to complete 3 different traces. BACKUP: https://academo.org/demos/virtual-oscilloscope/ EXTENSION: Attempt the questions on the sheet. These were from a paper in 2014. FF!

If you finish all that… Attempt the questions on the sheet. These were from a paper in 2014. These should be finished for homework. FF! Wednesday, 27 February 2019 12