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ENSC 120 (2014-3) Lab2

ENSC120 Lab Experiment 2 Getting to know Function Generator and Oscilloscope

Please read this document completely and thoroughly before you even touch any instrument.

Always handle the instruments gently. Use caution when you take the rolled-up probe leads, gently untangle

them and bring it to the bench area such that you can connect them to your circuit easily and conveniently.

Please don’t tug or snatch the probes.

Oscilloscope

Oscilloscope is an electronic graphing instrument that plots the voltage with respect to time. This is an essential

instrument to visualize ac signals and waveforms. Most scopes will have multiple inputs so that you can monitor

(plot) multiple signals at once. The TDS1012 scope you have on your lab bench has two inputs (Channels 1 and 2)

Familiarize yourself with the locations of the following buttons, knobs and pin:

CH1 MENU, Position and VOLTS/DIV knobs for CH1, CH2 MENU, Position and VOLTS/DIV knobs for CH2,

MEASURE, ACQUIRE, CURSOR, DISPLAY, AUTO SET, TRIG, Level knob, 5V@1kHz probe-calibration signal

output pin and the 5 buttons to the right side of the display screen. These 5 buttons are the On-Screen menu

selection buttons. Note the calibration pin set has a ground pin as well. Usually this pin is never used for your

experimetns.

The X-axis (the time axis) is controlled by the SEC/DIV knob.

The Y-axis (voltage axis) is controlled by the VOLTS/DIV knobs and there are two of them, one for each channel.

DISPLAY SCREEN

On-Screen Menu Selection Buttons

Calibration Signal Pin Ground Pin

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Gently take the probes from the blue container and untangle it. The probe leads and channel to which it is

connected can be identified using the coloured tab inserts on the wires. See images below

The probe end of the cable will have a hook-probe and an alligator clip. If you retract the plastic sleeve on the

probe you will see a golden coloured hook for connecting the probe to the circuit. See photo and inset below.

Always use a small stub of wire to connect the probe to the test point on the breadboard. The alligator clip is

usually connected to the ground or the common point of the circuit you are measuring.

Do not twist the probe wires Correct way to position the probe cables

CH1 Probe

CH2 Probe

Connecting Hook

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Operating the oscilloscope:

A. Turn ON the scope, the power button is on the top surface of the instrument at the left edge. The scope

takes a moment to go through the power-ON sequence.

B. Make sure the multiplier switch on the probe is set to 10X. See image below. Even if the multiplier switch is

in 10X, you move it to 1X and then switch it back to 10X. This operation will ensure connection.

C. Push CH1 MENU button once and observe the on-screen menu. From top to bottom the menu should be DC,

Off, Coarse, 10X, Off. If not, use the on-screen menu selection buttons to set the values.

D. Do the same for CH2. Push the CH2 MENU once. You will see the CH2 settings.

E. Connect both the probes to the 5V@1kHz probe calibration pin. See photo below. Connect both the hook-

probes to the top pin of the calibration. You need not connect the gator clips to the Ground.

F. Push the AUTOSET button. A moment later you will see two stationary waveforms appear on the screen.

Typically the CH1 trace will be on top and CH2 trace will be on the bottom on the display screen. The

channel numbers will be displayed to the left of the trace.

Channel numbers

Trigger Level Indicator Arrow.

In this case the trigger is

based on CH1

X-axis scale

In this case 500µs per div

Both hook-connections

are on the top pin

Y-axis scale for CH1

In this case 5 V per div

Y-axis scale for CH2

In this case 5 V per div

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G. At the bottom of the display you will see the CH1, CH2 volts/division settings and the Time-Base

seconds/division. The display will also have Pk-Pk (peak-to-peak value of the signal), Period, Mean and

Frequency of the waveform of CH1. This is due to the automatic measurement feature of the scope.

H. Since this is a calibration waveform, the scope should display a 5V Pk-Pk, 1kHz signal. Make sure the scope

displays this. If not, most likely you have not set the probe multiplier value correctly. Go back to step 2.

I. The signal display on the screen is also called as the TRACE of the scope.

J. You can adjust the vertical and horizontal size of the traces. To adjust the height of the trace use the

VOLTS/DIV knob. Rotate the CH1 VOLTS/DIV knob to see how the waveform display changes on the screen.

Note, the Volts/Div value for each channel change at the bottom of the screen when you rotate the knob.

K. Rotate the Position knob and you can see the entire waveform shift vertically. This control can be used to

move the traces to a convenient vertical location on the screen.

L. Try the above two steps for CH1 and CH2 to familiarize how the traces behave on the display screen for

these controls.

M. Now adjust the SEC/DIV knob and see the waveform stretch and contract depending on your choice. The X-

axis scale value, also known as Time-Base value, displayed on the bottom of the display will also change as

you rotate the knob. You will also notice when you change the SEC/DIV, both the traces will stretch and

contract simultaneously.

N. For best measurement using a scope you have to adjust the channel and time base settings such that the

screen shows three cycles of the waveform and each channel occupy 40% of the display screen vertically.

O. Push the AUTOSET once again and bring back the old display screen (step6).

Channel control and Trigger:

P. CH1 MENU and CH2 MENU buttons are Toggle buttons. If you push it once it will display the channel

settings. If you push the button once more it will turn off that channel. So, if you push the channel select

buttons twice consecutively it will turn OFF. To turn it ON, you have to push the button once again. Try

switching ON and OFF the channels. At the end of this trial display both the traces.

Q. Next, let us look at a feature called Trigger. Trigger is the feature that allows the scope to display the signal

like a stationary snapshot. This stationary trace (image) on the screen is needed so that you can make

meaningful measurements. The next few steps will teach you how to look into the trigger menu.

R. Press the TRIG MENU button. The on-screen menu will now change to TRIGGER display. Choose the trigger

source as CH1. Rotate the LEVEL knob above the TRIG button. You will notice an arrow on the right side of

the CH1 trace on the screen move up and down depending on your knob rotation.

S. Rotate the knob such that the trigger indicator arrow is well above the height of the CH1 trace. You will see

the scope looses its trigger and the waveform becomes un-steady. Bring the trigger indicator arrow back to

the original location and get a steady waveform.

T. Usually the AUTOSET feature will automatically set the trigger and give you a steady waveform. When the

input signal is too weak, or in some special conditions, the AUTOSET will not be able to set the trigger and

consequently you will notice an un-steady waveform on the screen. In that case, you have to go into the

trigger menu and adjust the trigger setting to get a steady waveform.

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Measuring signal parameters:

U. The main purpose of the oscilloscope is to observe the shape of the signal and also measure, particularly,

the amplitude and period. TDS1012 offers two features to make these measurements: using the CURSOR

button or automatic measurement. First we will see the CURSOR feature.

V. Press the CURSOR button. You will now see the on-screen menu display change to cursor menu. In this

menu you can choose voltage measurement or time measurement. Using the on-screen menu selection

button, choose CH1 as your source. Choose Voltage as the Type. Now two horizontal cursor bars will appear

on the screen. These two bars can be moved by the position knobs of CH1 and CH2. Adjust one cursor to the

top of the CH1 waveform and the other cursor to the bottom of the CH1 waveform. The Delta is the peak to

peak value of the CH1 trace. The individual cursor values will be shown in Cursor1 and Cursor2 window

below the Delta.

W. Now change the Type to Time. The cursors bars will now become vertical. Move the cursors such that you

can measure one period. The Delta display will show the period and the frequency. The accuracy of your

measurement will depend on the placement of the cursors. Therefore, you have to make sure you choose

the appropriate time base and vertical amplification (SEC/DIV and VOLTS/DIV) setting to display just the

necessary portion of the waveform as big as possible on the screen. Then use the cursors very carefully and

precisely to make the measurements.

X. If you want to make any measurements for the CH2 waveform, set the source to CH2 in cursor option and

do the measurements as described in the last two steps.

Y. If the signal waveform is a clean sinusoidal or square or triangular waveform, the scope has enough

intelligence to make measurements automatically. This can be done by pressing the MEASURE button.

Z. When you press MEASURE the on-screen menu will change. Using the on-screen menu selection buttons,

you can choose to display amplitude (Peak to peak) value and Frequency. Since this menu offers 5 display

windows, you can set the Pk-Pk and Frequency display values for both the channels. This measurement

option is usually good for very strong signals and the measurement values do not carry good accuracy.

However, this can be used for a quick check of your waveform values.

Cleaning up noisy signals:

AA. Some times you will have a steady waveform, but the trace will be very fuzzy. This happens when you are

measuring an extremely weak signal. If this happens you will not be able to determine the location or the

features of the signal to make good measurements. For this condition, the scope offers an averaging

feature. This can be initiated by pressing the ACQUIRE button.

BB. Push the ACQUIRE button. Once again you will see the on-screen menu change and you will see the scope is

set to Sample mode. You can change it to Average mode and also you can choose different number for

averaging. Basically the number indicates how many sweeps the scope averages to create the trace on the

screen.

CC. For good quality, set the Averages to 128 and select the Average. You will now see the waveforms become

very sharp and clean. With a sharp display you can make more precise measurements.

DD. Once you have made the measurements, set the acquire to Sample. If you don’t do this, the display will be

very sluggish and you cannot use the scope for further measurements.

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Please note:

This process of setting the multipler to 10X, connecting the probes to the calibration pins and pushing

AUTOSET is called “Calibrating the Scope”. Once you calibrate the scope, you should remove the probes

from the calibration pin and use it for your circuit measurement. At this stage you should never touch the

AUTOSET again. You have to use the control knobs and buttons of the scope for all adjustments and

measurements.

Never touch the AUTOSET button after you have calibrated the scope

unless you have a very strong signal for both channels.

How to download the SCOPE screen image to a computer

The Tektronix scope offers two options to download the signal traces to the computer. You can either get an

Image-Capture or a Data-Download. Image capture will get you a .bmp file (an image file) of the screen. Data

download will get you a .csv file that can be opened using EXCEL. With a .csv file you can re-plot the signal and

also edit the signal segments.

Before you start an image capture or data download, you have to calibrate the scope, measure the signal

properly and have the trace on the scope displaying a steady waveform. If necessary use ACQUIRE and AVERAGE

option to get a very sharp image on the screen.

Open the program OpenChoice .

This will open the Tektronix Interface Control program. You will notice this invoking several other programs, two

small windows pop-up from bottom right and disappear. Give it a moment and you will see the Tek window

open. Choose Select Instrument.

Select ASLR2 and click OK

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If you don’t see ASRL options, click cancel and open the Select Instrument once again and Choose ASRL2 and

click OK

Now you can click Get Screen and that will get you the scope screen shot as a .bmp image file. This will take

quite a while to download the image. Once the download is complete it will give you a save option.

Click Save As and save the .bmp file to a convenient location on your computer or your personal thumb drive.

Also give it a name that you can remember later.

If you want to download the scope image as a data file. Click the Waveform Data Capture from the top menu.

You will get a window as shown below

Choose CH1 and CH2 and click Get Data. This will take quite a while to download the data. Once the dialog is

complete, click Save As and save the .csv file. You can then use the excel file to plot the waveform.

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Function Generator: A function generator is an ac voltage source with a 50ΩΩΩΩ internal resistance.

This instrument produces the ac waveform for your experiments. It is capable of producing sinusoidal, triangular

and square waves. The amplitude, frequency and the DC offset is adjustable.

Make sure the BNC-connector is attached to the Main output. Gently take the probe and make sure the circuit

connection end is not shorted. See photos below.

a) Turn the power on

b) Push the blue SHIFT button and immediately push the RS232 button.

c) This will reset the FnGen and set-up the unit to 10kHz, 5V peak (10V peak to peak) sinusoidal signal with

zero DC offset.

d) Now connect the FnGen output probes to the Scope probes. Connect the Red mini-grabber pin to both

scope probe hooks. Connect the Black mini-grabber pin to both the alligator clips of the scope probes: see

photo below. Make sure the Red and Black connections do not short to each other. Place it on the desktop

such that you will not accidentally move it or disturb it.

Do not short these two probes

at any time

BNC Connector

Adjust knob

Adjust speed

switches

PWR switch

Hold button

to disable the

panel control

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e) You will now see two black patches on the scope screen. Adjust the SEC/DIV knob and the VOLTS/DIV knobs

of the scope until you see two identical waveforms one on top of the other on the scope screen. As I

mentioned before, adjust the scope settings such that you see three cycles of the waveform on the screen. If

necessary use trigger control to get a clean and stationary waveform on the screen.

f) To change the function, push the FUNC button. You will see the function toggle between the three types of

signal, sinusoidal, triangular and square wave cyclically. You should be able to see the waveform on the

scope screen. Bring the waveform back to sine wave.

g) To adjust the frequency, press FREQ. Now you can punch-in the frequency you want using the keypad and

complete the entry using one of the following keys [ MHz or kHz or Hz ]. For example, punch 1

followed by kHz. This will set the FnGen to 1 kHz output. The scope screen image will change. You have to

rotate the SEC/DIV knob anticlockwise to display a clean waveform display on the screen.

h) An alternatively way to adjust the frequency is to use the Adjust-Knob. You can dial up or dial down the

frequency. Slowly rotate the knob clock wise and anticlockwise to see how the frequency changes. You can

use the speed control buttons to make the change faster or smoother. Push the left side speed-adjust switch

once. Now rotate the knob to see how fast the frequency changes when you turn the knob. Do this again to

see how fast the frequency changes with the knob turning. Push the right hand side speed adjust switch

until the right most digit on the FnGen display blinks. Now rotate the knob and you will see the frequency

change very smoothly and also very slowly. Every time you adjust the frequency you also have to adjust the

SEC/DIV knob to make sure the screen displays at least 3 cycles of the steady waveform.

i) To adjust the amplitude, press AMPL. Press 3 followed by Vpp button. You will see the amplitude value

reduce on the FnGen display and also reflect this on the scope screen.

j) Press the right side speed adjust button until the right most display in the FnGen blinks. Now gently rotate

the knob clock wise and anticlockwise. You will see the amplitude go up and down and you can see this in

the scope waveform as well.

k) Similarly, the DC offset can be adjusted as well. Press the OFFSET button. The FnGen will display the offset as

zero. Now rotate the knob and you will see the DC offset change. If you rotate clock wise the scope

waveform trace will move up. If you rotate anticlockwise, the waveform trace will move down.

l) Bring the offset value back to zero. Do not disconnect the probes. You have to make a few measurements

and submit a record.

There are other capabilities that would be extremely useful for your future: particularly, using MATLAB to control the

FnGen and how to set automatic scanning of frequency. These can be found in the instrument manual placed in the Ref

Folder of the LabNet computers. When you have time go through them.

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Experiment and Record submission.

1. Open the Lab2_Record.pdf using FOXIT.

2. Reset the FnGen [See step (b) of FnGen operation].

3. Set the function generator to output a frequency of 5kHz sinusoidal signal and set the amplitude to 4V.

Record these values.

4. Since this signal is a strong signal you can use AUTOSET in scope to set the scope parameters. Push AUTOSET

button. This will automatically set the scope to display the signal on both channels of the scope. Makes sure

the scope display is steady and clean.

5. From the display, record the X-axis, Y-axes scales, CH1 Pk-Pk value and the Frequency.

6. Push the MEASURE button on the scope. Set the on screen measurement value displays from the top to

bottom as follows. CH1 Pk-Pk, CH1 Freq, CH2 Pk-Pk and CH2 Freq.

7. Record these four values.

8. Get a Screen-Capture of the scope display. Use the Tek-VISA program. Save the image file as 1.bmp

9. Push the CURSOR button on the scope. Set the Type to Voltage. Set the Source to CH1. Now move the

cursors using the position knobs such that one cursor is perfectly aligned to the top edge and the other

cursor is perfectly aligned to the bottom edge of the CH1 signal.

10. Now record the Delta value. Note the units as well. This is the measured pk-pk voltage value of CH1.

11. Get a Screen-Capture of the scope display. Use the Tek-VISA program. Save the image file as 2.bmp

12. Now set the Type to Time. You will see the cursors change to vertical. Move one cursor to perfectly align to

one of the top peaks of the CH1 signal. Move the next cursor to the adjacent peak exactly.

13. Now record the Delta value with units. This is the period of the CH1 signal. Calculate the frequency.

14. Get a Screen-Capture of the scope display. Use the Tek-VISA program. Save the image file as 3.bmp

15. Now press the AMPL button on the FnGen and set the amplitude value to 0.05V

16. Adjust the VOLTS/DIV knobs of the scope to increase the vertical size of the signal on the screen. Adjust both

the channels such that the trace shows reasonable size waveforms for both channels. The waveforms will be

very fuzzy and might be shaking or unsteady. Rotate the Trigger knob to get the image steady.

17. Press ACQUIRE button on the scope and average the signal for 128 samples and make the display sharp and

clean.

18. Now press the CURSOR button on the scope and set the Type to Voltage. Using cursors measure the pk-pk

voltage of CH1.

19. Record the Delta value.

20. Get a Screen-Capture of the scope display. Use the Tek-VISA program. Save the image file as 4.bmp

21. Attach the 4 image files to the Lab2_Record PDF file. See the demo video on how to attach an image to a

PDF file using FOXIT reader. Save the file and mail a copy to yourself.

22. Submit the Record through canvas.

23. Turn OFF the instruments, roll the probe cables and place them in their respective position. Clear the

desktop of any debris before you leave the lab.

Due dates:

LA 01 LA 02 LA 03 LA 04 LA 05 LA 06 LA 07 LA 08 LA09

22 Sept 23 Sept 24 Sept 25 Sept 29 Sept 30 Sept 01 Oct 02 Oct 23 Sept