Lab #4 – Oscilloscope Review / Name______
References: Tektronix. XYZ’s of Oscilloscopes. http://www.tek.com/Measurement/cgi-bin/framed.pl?Document=/Measurement/App_Notes/XYZs/&FrameSet=oscilloscopes
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Introduction: Please read this entire document before proceeding with the lab. Pay particular attention to the detail required for your conclusion. The oscilloscope, or scope for short, is one of the most versatile pieces of test equipment you will ever use. See Figure 1. The scope is used extensively in industry to tackle tough design projects or troubleshoot stubborn problems. Throughout your educational process, you will also use the scope quite extensively, and when you enter the job market, the scope should be second nature to you. This lab will familiarize you with the functional parts of the oscilloscope and the controls that go with them.
Objectives:
To adjust the vertical controls for the best waveform display.
To adjust the trigger level and slope for the best waveform display.
To make period and voltage measurements with the oscilloscope.
Part 1: Oscilloscope Basics (Detailed information on the oscilloscope can be found in the Tektronix oscilloscope guide, “XYZ’s of Oscilloscopes”)
Oscilloscope Screen: The oscilloscope screen is divided into sections to look like a graph. See Figure 2. The major divisions are 1 cm apart, and form squares much like a checker board. Each square is subdivided into five equal parts with tick marks or grid marks (2 mm in length). The actual scale of the graph is determined by the vertical and horizontal settings.
Vertical and Horizontal Controls: The middle section of the oscilloscope contains the vertical system controls. Using the vertical controls, two separate traces can be displayed on the osccilloscope grid, Channel 1 by itself, Channel 2 by itself, or both Channel 1 and 2 at the same time. The VOLTS/DIV selector switch determines the vertical scale of the major divisions (top to bottom) on the grid. The right side of the oscilloscope is divided into the horizontal system controls and the trigger system controls. The horizontal control, SEC/DIV, determines the horizontal scale of the major divisions (left to right) on the grid. No matter what Channel(s) is selected, the horizontal setting is the same for both.
Trigger Level and Slope:
The trigger level and slope controls provide the basic trigger point definition and determine how a waveform is displayed, as illustrated in Figure 3. The slope control determines whether the trigger point is on the rising or the falling edge of a signal. A rising edge is a positive slope and a falling edge is a negative slope The level control determines where on the edge the trigger point occurs.
Procedure:
1. This lab experiment will use a computer simulated oscilloscope and function generator. Download and install the Agilent Basic Instruments Emulator. Click on Start, Programs, Hewlett-Packard Instruments, HP54600B Demonstration. Turn on both instruments by clicking the Line button on the oscilloscope and the Power button on the function generator.
2. Connect the output of the function generator to the 1X channel of the oscilloscope by clicking on the BNC connectors of each instrument. Click on the Auto-Scale button of the oscilloscope to view the default waveform from the function generator. See Figure 4. List the settings of the oscilloscope below:
Vertical Sensitivity = ______mV/div, Horizontal Time Base = ______mS/Div
List the period, type of waveform, and peak to peak amplitude of the waveform below:
T = ______, Waveform type = ______, Vpp = ______
(Sine, Triangle or Square Wave)
3. Adjust your function generator to produce a 1KHz sine wave with an amplitude of 4Vpp. Click on the Auto-Scale button. Explain below the purpose of the Auto-Scale button:
Purpose of the Auto-Scale button:
List the settings of the oscilloscope below:
Vertical Sensitivity = ______V/div, Horizontal Time Base = ______mS/Div
4. According to the oscilloscope settings, what is the peak-to-peak amplitude of the waveform shown on the oscilloscope?
Vpp = ______
Note: This value should be twice the 4 Vpp value set on the function generator. The explaination of this doubling is that the function generator has an internal resistance (output impedance) of 50 ohms and assumes a 50 ohm load is connected. Since half the source voltage would be dropped across the internal resistance in this case, the function generator compensates by doubling its internal source voltage. The oscilloscope is a high impedance load, so the entire source voltage appears at the output. In most cases, it is best to change the settings of the generator for a high resistance load, so that the source voltage is not doubled. For the simulator, this setting cannot be changed.
5. Using the Level and Slope/Coupling Controls on the oscilloscope, obtain the other waveform displays illustrated in Figure 5. Note: The left and right mouse buttons control the turning direction of the instrument knobs.
6. Use the offset adjustment on your function generator to produce the waveforms shown in Figure 6. Note: The left and right mouse buttons control the turning direction of the instrument knobs.
7. Practice with the instruments by producing and displaying the following waveforms:
Triangle, 8Vpp, 100KHz
Square, 1Vpp, 20KHz
Sine, 500mVpp, 10KHz
Evaluation
Submit this completed lab worksheet along with a conclusion in Word format. For your conclusion, you need to learn how to “Print Screen” and “paste” your waveforms into a Word document. A “Print Screen” key is placed at various locations, depending on your model of computer keyboard. Once pasted into the document, you will need to “crop” the picture until only the scale information in the gray at the top of the trace and the green screen is showing in the picture. For each lab procedure, you will need to “Print Screen,” “paste,” and “crop.” Your pictures should look like the figures in this lab sheet with the addition of the scale information at the top. Label each picture appropriately (e.g., Figure 1 or Procedure 1) and add your conclusion in your own words. You should have 11 figures when you are finished: Procedure 2 (1), Procedure 3 (1), Procedure 5 (3), Procedure 6 (3), and Procedure 7 (3). A well written conclusion will refer to these figures in the discussion.
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