Hewlett Packard 546008 Oscilloscope Tutorial

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					IEEE Oscilloscope Tutorial      By Jason Long and Chris Yepes



    Hewlett Packard
  546008 Oscilloscope
        Tutorial




                 By Jason Long and
                    Chris Yepes
                IEEE, SEPTEMBER, 1999




                                                 Page 1 of 13
IEEE Oscilloscope Tutorial                                                                                        By Jason Long and Chris Yepes

TABLE OF CONTENTS

INTRODUCTION .........................................................................................................................................3
GETTING STARTED...................................................................................................................................4

SETUP ............................................................................................................................................................4

TAKING MEASUREMENTS......................................................................................................................6

HP SCOPE SOFTWARE .............................................................................................................................8

TRIGGERING...............................................................................................................................................9

APPENDIX 1: MENU FUNCTION DESCRIPTIONS ............................................................................11
   VOLTAGE MEASUREMENTS:.......................................................................................................................11
   TIME MEASUREMENTS: ..............................................................................................................................12
   CURSORS:...................................................................................................................................................12
   TRIGGER → SOURCE BUTTON:...................................................................................................................13
   1 <OR> 2:...................................................................................................................................................13
   ± (CHANNEL MATH)...................................................................................................................................13




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IEEE Oscilloscope Tutorial            By Jason Long and Chris Yepes

INTRODUCTION
     An oscilloscope is used to display circuit
voltages.     It can measure and show any DC or
oscillating   voltage  and  provide  the  user   with
measurement of the voltage level, frequency, period,
etc.    The HP 546008 is capable of displaying two
separate waveforms at once, so it can be used to
compare, say, the input vs. output voltage of a
circuit. The instrument works by sampling the voltage
levels of the signals it is receiving and displaying
the information on screen.

     This tutorial provides an introduction on how to
use the oscilloscope – the HP 546008, available to
undergrad students in Engineering at the University of
Calgary.    It covers the basics of setting up the
oscilloscope properly, adjusting the instrument to
display data correctly, and using the built-in features
to measure and record data.     The overall goal is to
prevent some of the confusion that may be experienced
during the many labs that you will complete.        The
information presented here is fully applicable to the
new scopes in A305, even though they’re a newer model.

     The first word of advice is that the TA’s who run
the lab are there to help you if you have any questions
about the equipment presented to you. They are a very
valuable resource, and will be happy to assist you in
any way they can – make sure you take advantage of
this!! However, in a crowded lab with only one or two
TA’s, you may find the knowledge that this tutorial
will provide to be very helpful when no one else is
around.   Though you won’t be experts, by the end of
this tutorial you should know everything necessary to
successfully use the oscilloscope throughout your first
few years of Engineering labs (you may want to print
this out and bring it along with you when you begin
your lab sessions). Bon appetite!!




                                                       Page 3 of 13
IEEE Oscilloscope Tutorial                    By Jason Long and Chris Yepes

GETTING STARTED
     When you enter the lab, all the equipment at the
stations should be turned off – turning everything on
is an excellent place to get started.
The first thing that you will learn in
lab 1 of ENEL 341 is that each station
has a master power switch – it looks
kind of like a light switch with a red
light that will turn on with the switch. I assure you,
you will be expected to know this, though no one will
ever tell you about it…    Switch the master power on,
then turn the oscilloscope on with the white button
marked Line (see Figure 1).     The oscilloscope screen
should light up with the HP logo, and the scope will go
through its boot sequence.

SETUP
     On the front panel of the instrument, there are
three co-axial inputs, marked 1 X, 2 Y, and External
Trigger. Inputs 1 and 2 (see
Figure   2)   are   where   the
signal sources are plugged
into; don’t worry about the
External    Trigger.        The
connecting   wires    must   be
either    a    regular    co-ax
connection cable or a voltage probe. The regular co-ax
cable can be used to link another instrument to the
scope, or can plug into one of the ports on the
prototyping centers.     Probes are used to connect to
individual points on a circuit.     For example, if you
wanted to look at the voltage at a certain terminal of
a resistor, you would simply clip the probe to that
point.

                                  After plugging in the wire,
                             you   must  configure   the  input
                             source. Press the numbered button
                             to bring up the on-screen menu for
                             the source you’re dealing with.
                             For now, the only things that you
                             need to play with on this menu are
                             the input type and the on/off

                                                               Page 4 of 13
IEEE Oscilloscope Tutorial               By Jason Long and Chris Yepes

select. Make sure the source is active – this can be
toggled with the first menu button.    Next, select the
Probe button and remember this next sentence: If you
are using an input probe, you must set the input to
10X. Why? The technical explanation is that for some
reason   the  probes   multiply  the   voltage  they’re
measuring by 10, so the oscilloscope will display 4V as
40V if the 10X is not selected. This is something you
will learn in lab 2 of ENEL341 after you think you’ve
built an amazing amplifier out of only a few resistors
and a capacitor!!

     Once you’ve correctly set up the input source, you
can make it look nice on the screen. There are three
knobs for each input source (see Figure 3) to turn to
make this happen: Volts / div, Position and Time / div.
Here’s what they all do:

    •   Volts / div: This changes the scale of the
        vertical axis, which in effect makes your signal
        waveform appear taller or shorter.    The current
        setting is shown in the top left corner of the
        screen. For example, a setting of 500mV indicates
        that each division on the screen is worth 500mV.
        Whenever     you     are
        scoping a signal, the
        entire waveform needs
        to be visible in the
        screen. Note: each of
        the two inputs can be
        set   to   a   different
        scale,       so      the
        appearance      of   the
        waveforms            can
        sometimes             be
        misleading – always be aware of the scale before
        drawing any conclusions!!

    •   Position: Depending on the application, you may
        want to move your wave around the screen. This is
        useful when comparing periods of waves or when
        looking at a square wave for digital circuits.
        Rotating the knob will move the wave up and down
        on the screen. An important thing to note is the
        small arrow on the right side of the screen which
        indicates where 0V is on the waveform.
                                                          Page 5 of 13
IEEE Oscilloscope Tutorial               By Jason Long and Chris Yepes


    •   Time / div: This works just like the Volts / div
        except it changes the horizontal (time) axis
        scale.   When examining a particular signal, you
        should have at least one full period of the lowest
        frequency wave visible on screen – adjust the Time
        / div accordingly during your experiments.

One   additional    and   sometimes   useful    function
(particularly for Computer Science or Management
students) is the Auto Scale button.       Pressing this
button will automatically set the scope to display the
waveforms in such a way that HP thinks is best. 50% of
the time, this works well, the rest of the time it
makes things worse. If you do use the Auto Scale, make
sure you note any change to your axis scales and wave
positions before you draw any conclusions from what you
see!! *Note: I’ve been told that real engineers never
use the Auto Scale…

TAKING MEASUREMENTS
     The oscilloscope can display measurements of the
voltage and frequency for any
signal it is receiving.         By
default, no measurements will be
shown on the screen, though you
can    get  a    relatively   good
approximation from the grid.    Where more precision is
required, the scope can help.       At the top of the
control panel, there are three buttons of importance
under the heading Measure (see Figure 4). The buttons
are marked Voltage, Time and Cursors and are used to
bring up the menus used for selecting what measurements
you want the scope to display.      *A complete list of
menu options is provided in Appendix 1.

     Obviously, pressing the Voltage button will bring
up the options for measuring the voltage of your waves.
The menu buttons (see Figure 4.5), allow you to toggle
                                    between   the    two
                                    signals and display
                                                 various
                                    measurements     for
                                    each.   Most often,

                                                          Page 6 of 13
IEEE Oscilloscope Tutorial             By Jason Long and Chris Yepes

you’ll want to know the Peak-to-Peak Voltage, Vp-p,
which measures the voltage gap between the highest and
lowest points on the wave. (Note that if Vp-p= 5V, that
doesn’t mean the maximum of the wave is at 5V; it’s
more likely at 2.5V – be careful!!).         The other
measurement that you’ll probably use often is Vavg,
which will show you the average voltage level in your
wave.

     Similarly, pressing the Time button will bring up
the menu for measuring things such as the frequency and
period of the wave. Again, select which wave you want
to measure with the menu buttons.        Thought these
features are quite self-explanatory, Appendix 1 details
each function available.

     You can display up to four different measurements
at once on the screen that work in real time.      It is
handy to always show Vp-p and the frequency of the waves
you are displaying, so it is a good habit to get into
to always set up these measurements for display when
you begin an experiment.




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IEEE Oscilloscope Tutorial            By Jason Long and Chris Yepes

     Cursors are used to measure the horizontal or
vertical offsets (in other words, the distance) between
two points on the screen. Most of the time, this will
be handy to determine the phase angle (amount by which
one signal leads or lags the other) of two signals.
Pressing the Cursors button will cause two vertical
lines to appear on-screen.    A menu to switch between
the cursors and provide measurements is also available.
The cursors can be moved back and forth using the knob
located below the cursors button (this knob is not
labeled for some reason). The menu buttons are used to
select which cursor is active and thus which one is
moved by the knob.

     Horizontal cursors are also available if you need
to measure differences between two vertical points of a
signal or for visually comparing height variations of
two signals. The cursors menu provides the options for
selecting this feature, and moving them is again
accomplished with the knob.

HP SCOPE SOFTWARE
     A somewhat nifty feature of your workstation is
the link that is maintained between the PC and the
oscilloscope. This allows software on the computer to
talk to the scope and extract information from it. As
far as my second year labs ever went, the main use for
this feature was to obtain a print-out of the scope
screen for use in your lab write-ups.

     Getting  the  PC   to   talk  to  the  scope  is
surprisingly easy.   The only hard part is if none of
your group members has an Electrical Engineering
computer account that is necessary to log on to the
computer (may I recall yet another ENEL341 lab
disaster…).   The software you need to be running is
called HP Scope – you should see the icon on the NT
desktop.

     Collecting data is a matter of selecting the
command from the pull-down menu once the software is
running.    You can choose to get only channel one,
channel two or both channels from the scope. Whatever
you select, it takes about 20 seconds to complete the

                                                       Page 8 of 13
IEEE Oscilloscope Tutorial                 By Jason Long and Chris Yepes

download. The scope screen should freeze and give you
a message that it is being polled for data. The graph
will then come up on the computer screen. If you want,
you can customize the title and axis names, etc. which
is easy to figure out and do.

     Printing the graph is easy as well except for one
catch: make sure you print everything you need during
your lab period.    Your ENEL computing account allows
access to printers only during your scheduled lab
times. That means that if you discover you’re missing
a graph the night before your lab’s due, you’re SOL!!
(This can only be avoided by purchasing extra printing
pages from the ENEL computing office (room A12, I
think) – when you get your account you might want to
inquire!! . Try not to waste too much paper – you only
need to print out graphs that you’ll actually use.
Hand-drawn versions are happily accepted by the TA’s in
most   cases,  unless   a  print-out   is  specifically
requested.

TRIGGERING
     Most of the time, the signals that are displayed
by the oscilloscope will be friendly.    That is, they
will not be fuzzy, they will not be moving around and
they will not make fun of you. However, depending on
factors such as the circuit you’re using, the
frequencies you’re measuring and other things, you may
get unfriendly signals.

     One   way   to   deal   with   such
instances of evil, is to play with
the Trigger buttons and knobs (see
Figure 5). The trigger has something
to do with the sampling rate or time
that the scope is using to look at
your signal.      Fooling around with
these settings is one way that I’ve
discovered    to   fix   fuzziness    or
roaming signals. You can play around
without    worrying    about    damaging
anything, and sometimes you’ll get
lucky and fix your problem.


                                                            Page 9 of 13
IEEE Oscilloscope Tutorial                                       By Jason Long and Chris Yepes

     In most cases of ugly signal displays or for any
other problems that you can’t figure out, it is
probably a good idea to get a lab TA to help you fix
it.

     The rest of the buttons and gadgets on the HP
546008 are a mystery to me (except for the screen
brightness knob).     I would assume that your lab
assignments will be similar to the ones of the past, so
the skills that you’ve learned here should be ample as
a foundation for completing the laboratories. The best
advice is to practice and play and to do things for
yourself.   If a lab TA ever does something for you
(that sounds a little too negative), make sure you can
do it yourself without help!! The labs are open almost
all the time – don’t be afraid to experiment.      Most
importantly, have fun!!




If you have any questions or comments, please email Jason at ieeesb@ucalgary.ca




                                                                                  Page 10 of 13
IEEE Oscilloscope Tutorial              By Jason Long and Chris Yepes

APPENDIX 1: MENU FUNCTION DESCRIPTIONS
Using the Voltage, Time and Cursor buttons on the HP
Oscilloscope brings up a variety of different options
that you can use to extract data from your wave trace.
A   few    of    the
common       options
have already been
described in the
tutorial, but this
appendix lists all
of     the      menu
options    with    a
short   description
of each.    It also
describes        the
features available
for      Triggering
options, and the
functions      shown
when pressing the
“1 or 2” and “±”
buttons.    Recall that the various measurements are
selected using the buttons at the bottom of the screen
as shown in the picture (the menu shown is for time
measurements).


Voltage Measurements:
  •   Source 1 / 2: Selects which source (channel 1 or
      channel 2) to which the next selected option will
      apply.
  •   Vp-p: Measures the potential difference between the
      highest and lowest points on the wave.
  •   Vavg: Calculates and displays the average voltage
      in the wave. This will often be 0 for oscillating
      waveforms unless they wave a DC component.
  •   Vrms: Calculates and displays the RMS (root mean
      squared) value of the voltage.
  •   Clear Meas: Clears all the current measurements
      that are on the screen.
  •   Next Menu: Brings up the second screen of available
      voltage measurements.
  •   Show Meas On / Off: Toggles the measurements
      displayed on or off.

                                                        Page 11 of 13
IEEE Oscilloscope Tutorial              By Jason Long and Chris Yepes

  •   Vmax: Computes and displays the voltage at the
      highest point in the wave.
  •   Vmin: Computes and displays the voltage at the
      lowest point in the wave.
  •   Vtop:
  •   Vbase:
  •   Prev Menu: Returns to the first set of Voltage menu
      options.


Time Measurements:
  •   Source 1 / 2: Selects which source (channel 1 or
      channel 2) to which the next selected option will
      apply.
  •   Freq: Calculates and displays the frequency of the
      selected source.
  •   Period: Calculates and displays the period of the
      selected source.
  •   Duty Cy:
  •   Clear Meas: Clears all the current measurements
      that are on the screen.
  •   Next Menu: Activates the second screen of available
      time measurements.
  •   Show Meas On / Off: Toggles the measurements
      displayed on or off.
  •   t width:
  •   -width:
  •   Rise Time: Calculates and displays the total amount
      of time that the waveform is increasing (dv/dt >
      0).
  •   Fall Time: Calculates and displays the total amount
      of time that the waveform is decreasing (dv/dt <
      0).
  •   Prev menu: Returns to the first set of Time menu
      options.


Cursors:
  •   Source 1 / 2: Selects which source (channel 1 or
      channel 2) to which the next selected option will
      apply.
  •   (horizontal) v1: Make the first cursor active. The
      cursor that appears on screen will be horizontal,
      and thus measures height differences in the wave.
  •   (horizontal) v2: Make the second cursor active.
      Note that the calculations between two cursors are
                                                        Page 12 of 13
IEEE Oscilloscope Tutorial               By Jason Long and Chris Yepes

      dependant on their relative positions (that is, if
      V2 is above V1, then ∆v will be negative – be
      careful).
  •   (vertical) t1: Make the first cursor active.    The
      cursor that appears on screen will be vertical, and
      thus measures phase differences in the wave.
  •   (vertical) t2: Make the second cursor active. Note
      that the calculations between two cursors are
      dependant on their relative positions (that is, if
      t2 is behind t1, then ∆t will be negative – be
      careful that you’re aware of what you’re looking
      at).
  •   Clear Cursors: Clears the cursors off of the
      screen.


Trigger → Source Button:
  •   1: Use channel 1 as triggering source.
  •   2: Use channel 2 as triggering source.
  •   Ext: Use an external trigger (must supply input to
      External Trigger).
  •   Line: Use line trigger.


1 <or> 2:
  •   1 <or> 2 Off / On: Turn the selected channel on or
       off.
  •   Coupling DC AC    :
  •   BW Lim OFF / ON:
  •   Invert OFF / ON: Inverts the signal (i.e. 5V becomes
       –5V).
  •   Vernier OFF / ON:
  •   Probe: Selects the multiplying effect of the probe.
       In out labs, the probes are 10X, so this selection
       must be highlighted.


± (Channel Math)
  •   Off: turns any channel math off.
  •   1+2: Adds the signals from channel 1 and channel
      two and displays the resulting waveform on screen.
  •   1-2: Subtracts the signals from channel 1 and
      channel two and displays the resulting waveform on
      screen.


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