ECE3424 Electronics Laboratory
Experiment #0
GETTING STARTED:
Workstation instrumentation and Prototyping environment
vers 2.2
Intent: Make an assessment of the environment. Run a snake check on cables and instrumentation and a
preflight status check of the workstation. Check out the features and capabilities of the instrumentation
cluster.
Your workstation is centered around a cluster of the following instruments:
1. Digital Multimeter: Serves as (a) DC or AC voltmeter (b) Ohmmeter, (c) DC or AC
ammeter.
2. Power Supply: Three outputs: (a) 5V fixed, (b) 0-20VDC variable (c) 0-20 VDC
variable.
3. Function Generator: Provides an electrical signal that is periodic in form of three basic
types: (a) square (b) triangular (c) sinusoidal (d) special applications, and can accomplish modulation and
sweep of these waveforms.
4. Oscilloscope: Multipurpose instrument for viewing the voltage V(t) of any node. It has two
input channels which are under the control of a time sweep channel. It has lots of knobs and buttons and
menu options and is smarter than the average engineer.
5. Prototyping platform (MFJ Box): This box is the operational platform for the experiments.
It includes (a) an internal power supply (b) an internal function generator (c) a set of 8 switches arranged
as a byte (d) a set of 8 lights arranged as a byte (e) several interface connectors and switches (f) two
potentiometers. The working space of the prototyping platform is a site where a prototyping whiteboard
may be emplaced using velcro strips.
The workstation will look something like that shown by figure 1. It is a 6' lab workbench. Take
particular note of the fact that under the counter there are two drawers that contain cables and wires
necessary for hookup of the instrument cluster to the experiment.
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The instrument cluster is the operational environment for execution of tests and experiments. As shown
by Figure 2 it is made up of the 5 basic instruments identified earlier.
You might take note that different instruments will have different connector terminals specific to their
usage. Instrument I/O connectors are always female connectors. The ones that you will encounter are
shown by figure 3b. The corresponding male connectors are identified by figure 3a.
If there are incompatibilities in connector pairs it may take a few patches to accomplish a simple
connection. The simplest way to do so is to use the "alligator clip" (see figure 3a).
The preferred way to connect up a circuit is via the prototyping board (protoboard) of figure 4 and this is
the platform that we populate for each experiment.
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THE MEASUREMENT INSTRUMENTS:
Most of its features are self-explanatory.
*The one that will give you the most trouble is (4). You will forget to push it or un-push it.
+Caution: The ammeter input (2) has zero internal resistance. Make sure that you do not apply it
to a voltage source or you may burn up both the source and the meter.
The Volt/Ohm input (1) is the setting that you will use most often. This input essentially has
~infinite internal resistance. It is designed to be used with voltage probe cables (figure 5b).
The DMM inputs accept either banana plug cables or the voltage probes (as shown).
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Most of its features are self explanatory.
You should take note that there are three power supplies in the box. (1) is usually used to support digital
circuits, whereas (2) and (3) are usually used for analog (amplifier and device evaluation) applications
Pushbuttons (4) defines which of the power supplies (1), (2) or (3) will be displayed on the meter (5).
Output controls (7) are associated with power supplies (1) (2) and (3), respectively.
Pay particular attention to switch (6). This switch will enable one power supply to be “slaved” to the
other, i.e. one supply will track the other, same voltage one-to-one. This feature is particularly important
when we desire to have power rails that are ‘bipolar’, i.e. (+,-) V, with a GND (common node) between
and we desire to vary these voltage supply rails concurrently.
The only feature that will give you any trouble is (8). This is the internal GND. It must occasionally be
connected to one polarity or another for the use of the three power supplies concurrently.
Notice that the inputs only accept banana plug cables. Wires can be clamped into the terminals but this is
usually more trouble than it’s worth.
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SIGNAL GENERATOR (AWG) Agilent 33521A
The Agilent 33521A is a menu-driven instrument with the local screen display toggled by magnitude
levels selected by the function keys (6) consistent with the type waveform as selected by the button keys
(7). Specific values are set using the numeric keypad (10) and second-level screen display options.
Most of the operational features are denoted by text and icons and are reasonably self-explanatory. The
main output is taken from (16) which is toggled on/off by the channel button just above (16). Since you
have a single-channel output (the Agilent 33521A) you will only have one output channel and it will be
located at site (16). Waveform type and the parameter selects are determined by the pushbuttons (7). At
the beginning all you should do is figure out how to call up a sine wave and set its amplitude and
frequency, and then toggle it along to the oscilloscope.
Much of what the AWG (arbitrary waveform generator) can do must be ascertained by discovery.
Although you will be taken through the basics, the rest of the story will call for a walk down any and all
of the paths that this instrument offers. The AWG can realize a good many signal and sweep offerings,
and your task, should you choose to accept it, is to investigate any and all of its capabilities and have
them ready for service in the set of circuit and device tests called for by the experiments.
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Tektronix TDS 202C OSCILLOSCOPE
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The oscilloscope is a viewport that is usually used to view signals tapped out from a node of interest. For
a high-quality instrument such as this one the probes are non-intrusive and will not induce any
measurement artifacts. For more sensitive measurement situations higher quality low capacitance probes
are employed, but since the lab does not usually need them they are left in the background while alligatorclip probes are clipped to the circuit or device under test.
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You might take note of the fact that the MFJ box has several of its own internal instruments. (1)
corresponds to a power supply, fixed voltages of (+,-) 12 and 5VDC. (2) is a signal generator. It may
have some mild distortions in the sinusoidal output. (3) is a clock pulse output, with three fixedfrequency settings. (4a) and (4b) are some internal potentiometers, handy for some types of
experiments. (5) is a single-pulse output.
For logic experiments there is a `byte' of input switches (6) and a `byte' of output indicators (7). These
are usually used in conjunction with (3) and (5).
(9) is a push-button switch and (10) is a means to make connections off-panel to other instruments.
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Incoming status check: (before each experiment) If your predecessor has left the workstation in good
order and in the standard conclusion mode settings listed below you should be able to do a status check in
a glance.
(1) Check out the power supply via the DMM and confirm (1) power supply output and (2) tracking
of the +20 and -20 voltage supply rails.
(2) Check out the function generator via the Oscope. Set it for a sinusoidal output of 1 kHz with zero
and amplitude at 1.0 Vp-p on Ch1. If necessary initialize the O-scope by the ‘autoset’ button. Then
make a quick check to ensure that the offsets, amplitude controls, and (Oscope) amplifiers are functioning
correctly.
(3) Check out cables, and make sure that they do pass signals with no weakness or intermittent loss.
Cables are a common villain in the loss of workstation integrity.
Conclusion settings: at the end of every lab session
Restore the instrument cluster to ready-mode settings (listed below). Leave instruments ON and waiting
for the next user even if the next lab section meeting is next day or next week.
(a) Power supply:
Voltage: 10V.
Display switch: 20V
Tracking: Independent
(b) DMM:
Option: Volts DC
Range: 20
(c) Function Generator:
Frequency: 1 kHz (range = 103).
Type: sinusoidal
Offset: null position
Amplitude: 1.0 Vp-p
(d) Oscilloscope:
Offsets:
Settings:
Ch1: 1cm above axis,
Ch2: 1 cm below axis
Ch1: 500 mV Ch 2: 500 mV, M: 500 us
trig'd M Pos: 0.000
CH1:
coupling DC BW limit: OFF Volts/div: Coarse Probe 1x
Trigger: Edge slope: rising Mode: Auto Coupling DC
(2) Return (a) cables to right drawer and (b) wires to right drawer for use by the next person.
It is necessary and essential that we following this regimen in order that you and your brethren and
sisteren can start up each lab experiment with maximum confidence in the instrument cluster, minimum
incoming operational problems and minimum start-up overhead.
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GETTING ACQUAINTED WITH THE INSTRUMENT CLUSTER (PROCEDURE):
I. Power Supply and Digital Multimeter
A. Set up the power-supply and DMM as shown by figure I-A-1. Set the tracking switch to
independent. Set 20V voltage supply to 8V as defined by the meter on the power supply. Measure this
value using the DMM (is it the same?). Repeat for 12V, 16V and 20V. Enter data in a short table.
B. Repeat for the -20V power supply. Note that you will have to change the ‘display’ switch on
the power supply.
You have just performed a calibration of the two power supply variable sources. Hopefully both are
linear.
C. Set the tracking switch to parallel and the display switch to 20V. Adjust the 20V power
supply to 8V, 12V, 16V and 20V, respectively. Using the DMM alternately between (+20V, -20V) and
toggling the display switch, record in a short table, V+ for display output, V- for display output, V+ for
DMM, V- for DMM. These should correlate. This process is the calibration of the tracking mode.
Figure I-A-1. Instrumentation check
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II. Function Generator (AWG) and Oscilloscope
A. Set up the function generator and Oscilloscope as shown by figure II-A-1.
B. Use the function generator menu and screen to set the function to sinusoidal, with frequency = 1.0
kHz, offset 0.0, and amplitude setting 1.0Vp-p. Push the ‘autoset’ button on the Oscope, which should
give a clear clean display of this waverform. The the autoset has not done so adjust the offset for CH1 of
the Oscope so that the marker falls 1 cm above the median. Measure peak-peak voltage of the sine wave
by means of the V/cm scale and the ‘measure’ button. Is it anywhere close to the amplitude setting of the
function generator? (why not?). While you are in this setting check out the effect of the ‘offset’ of the
function generator.
*The AWG is designed for an output load of 50standard. So it is necessary to include a (BNC) ‘tee’
with a 50 load on one of the tee outputs as shown by the figure below. If these output accessories are
available (the tee and the 50 load) then attach as shown repeat the measurements of part B.
Check your trigger menu. It should be set for: Type: edge, Source: CH1, Slope: rising , Mode: Auto,
Coupling: DC. If it is not at these settings, then reset them accordingly. Adjust the horizontal
positioning knob (tie scale) and you will see the reference marker (on the upper axis) translate
accordingly. Set it to 0.000.
C. Measure the period of the sine wave using (a) ttime scale (500 s/cm, or 50ms full screen) and the
cursors*, and (b) the ‘measure’ button. Take the inverse to determine f. It should be close to 1.0 kHz if
not exactly, since these are digital instruments. Reset the function generator to f = 2kHz and 5kHz
respectively, and repeat the O-scope to measure period and frequency and record in a short (Excel) table.
Change time scale of the Oscope as needed. Reset the AWG function generator to 10kHz, 100kHz,
1MHz, respectively. This procedure is a typical calibration sequence for the time scale.
*The cursor menu is invoked by the ‘cursor’ button (second row of buttons from the top). If you push the
button adjacent to the screen sidebar menu labeled as ‘Type’ you will invoke the cursors and be able to
select either the y-axis scale (Amplitude) or the x-axis scale (Time). The knob at the upper center of the
panel controls the cursor position and the sidebar menu will the display the position coordinate value of
the cursor(s).
D. Repeat part C for a signal taken off of the ‘pulse’ output of the function generator (it is under the
‘waveform’ button). For the 1kHz frequency select a pulse width (under the ‘parameters’ button) of
250s. Continuing with other frequencies select a pulse width of 0.25 x T (= period) for each frequency.
Frequency assessment will be nearly the same, but more accurate since the pulse interval is usually an
easier read than the sinusoidal period. Check and confirm pulse width as well as the frequency.
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There should not be any great surprises unless your instrument has drifted out of calibration.
Figure II-A-1. Instrumentation check
E. Reset function generator to 1.0 kHz and 1.0Vp-p amplitude. Connect CH2 to the output from the
internal signal generator of the MFJ box, set to sinusoidal. You may have to do some patching to make
these connections. Adjust amplitude of CH2 display so that it is nearly the same as that for CH1.
Find the X-Y setting for the Oscope (look under the display menu) and invoke this setting. An X-Y
pattern is generated is of the form of a "Lissajous" figure. The Lissajous figure is used to compare two
signals. If they are different frequencies you will see a “rotating” pattern. Tune the MFJ frequency so
that the pattern stops "rotating". When the pattern becomes stationary, the frequencies are synchronized.
Adjust the amplitudes (and frequency) so that the figure is a perfect "O". If any distortion is present then
it will show up as an imperfect "O" (or an imperfect ellipse).
F. Change the frequency of the MFJ box to 4kHz and synchronize to that from the Agilent 33521
function generator. Make a sketch of the pattern. Now change the frequency of the function generator to
4 kHz synchronizing it to the MFJ box. Find the display setting, change to YT, triggered by CH1, and
measure the period. It should be almost exactly 0.25 ms, because you have used synchronization to reset
your signal frequency from 1kHz to 2 kHz. This process can be done a good bit more efficiently with
electronics using a technique called "mode locking" and is the basis for most of the uplinks to satellite
communications and GPS systems. It is also the technique used to make audio synthesizers (which
require precise harmonics).
G. Using the DMM and its `probe' cables, probe the sinusoidal output of the function generator with the
DMM set to ACV. Repeat for outputs from the function generator of Vout = 2V, 5V respectively, and
record results in a short table. In the table, compare 0.5*Vp-p of the Oscope display value with the ACV
reading on the DMM. The DMM measurement is the RMS (root-mean-square) value of the periodic
function. For sinusoidal output VRMS is approx 0.707 x V(peak).
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ADVANCED USAGE of the AWG
There is not much entertainment with the Oscope since it is mostly a viewport. However the AWG will
generate as many exotic waveforms as there are chords on a guitar. Otherwise it may be regarded as a
source of waveforms and waveform options that serve to exact a complete test and evaluation of circuits
and devices, which is the charter of the set of lab experiments.
The feature of principal interest is the frequency sweep function. It requires a little more setup but is a
real timesaver in the measurement of diode and transistor parasitic capacitances.
With the waveform set to a sinusoidal f = 1kHz and amplitude 1.0 Vp-p (as before), push the ‘sweep’
button and bring up its menu bar. Toggle the necessary buttons below the menu bar to accomplish the
following settings:
Type:
Start freq:
Stop freq:
Sweep time:
linear
1 kHz
10kHz
10 ms
On your O-scope set the time scale to 100s (per cm). The trace you see will display the signature
pattern for a sweep frequency on a linear time scale, and is used as a confirmation of frequency sweep.
Later in life you will be expected to choose an AWG frequency sweep on the order of 10kHz to 1MHz for
an Oscope sweep time of 1ms/cm with the full screen window of the O-scope 10 x 1ms.
Get check-off from your instructor on all of these tests and data as you march through them.
This is called an "informal report". This checkoff report has value of approx 50% of experiments that
include a written laboratory report.
**At the conclusion of the experiment please attend to the proper close-out procedure (page 10). Your
brethren and sisteren will appreciate your attention to this courtesy.
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