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8/10/2019 06 Lecture #2.ppt
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Lecture #2
Oscilloscopes 2
ComparatorsEE 211
Clarkson University
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Scope 2 topics
Dual Trace Operation
X-Y plots
Phase angle measurement
Equipment:
decade capacitor
10kWdecade resistor
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Decade resistor.
Note the 3 studsredand black connect to
the resistances.
Check with an
ohmmeter.
The silver stud is case
ground, it is there for
safety and forshielding.
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Voltage Divider RC circuit used in
the lab
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Analysis of RL circuit
1
CL CL
L
CLout in
CL L
Z jX
j C
ZV VZ R
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Two Channel Oscilloscope
Operation Phase Angles
Mathematical Options
Differential Voltage Measurement
X-Y plots
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Phase Angle Measurement (1)
Time
1.0ms 1.2ms 1.4ms 1.6ms 1.8ms 2.0ms
V(200) V(300)
-1.0V
0V
1.0V
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Phase Angle Measurements (2)
Time
1.0ms 1.2ms 1.4ms 1.6ms 1.8ms 2.0ms
V(200) V(300)
1.0V
0V
1.0V
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Lissajous Figures
(qArcsin(A/B))
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Before Lab
Calculate the value of CLfor Step 2.
Calculate the values of RLfor the 4 angles
given in Step 18.
Review the oscilloscope material referenced
on the course web site.
(optional) Review Lissajous diagrams on
the web.
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Lab 4. Comparators
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Determine pins with an ohmmeter
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Circuit #1
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Protoboards
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Op Amp troubleshooting guide
1. Check power supply voltage to the opampwith voltmeter
2. Check Vout on the scopemake sure youare on dc coupling. Keep this trace on thescreen
3. Check the non-inverting and invertinginputsare they the same (should they bethe same?)
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Op Amp troubleshooting (#2)
5. If the output is on one of the rails, groundboth input terminals, the output should go
to zero6. Should the op amp be in the linear region,
but is not? Check your circuitparticularly the feedback circuit.
7. No output at all? Set it up as acomparator, and recheck output.
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Troubleshooting Tips
Measure voltagesvisual inspections are
not reliable.
Think of complex circuits as a set ofsubcircuits, and check each subcircuit
individually.
Dont ignore the ground bus--
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What Happens?
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What Happens?
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Schmitt Trigger circuit
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Schmitt trigger equations
inf
f
s
inf
inout
s
inf
insout
RR
RV
RR
RV
VRR
RVVV
)(
hysteresis term scaling term
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Example
If Vout is either +12v or -12v
and Rf = 11*Rin
Then the hysteresis term will be + 1volt
(Note: scaling does not matter when the
inverting input is set to zero)
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Schmitt Trigger w/noise
Time
0s 10ms 20ms 30ms 40ms 50msV(200) V(100)*5
-20V
0V
20V
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Schmitt Trig.-Vout vs. Vin
V(100)
-3.0V -2.0V -1.0V -0.0V 1.0V 2.0V 3.0V
V(200)
-10V
0V
10V
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Writing Assignment
Review LABORATORY REPORT STYLEGUIDE on the course web site
The second writing assignment will be towrite a section presenting data from Step Gof the comparator lab, on Schmitt triggers.
Present a table showing the comparisonbetween predicted and measured deadbandsof the Schmitt triggers you build.
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Assignment
Include a single paragraph discussing the
results that are presented in the table.
Do not discuss Schmitt trigger theory oryour lab procedure.
Do discuss the quality of your results
comment on the accuracy or lack ofaccuracy.
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Details
Due date 3 working days, during your next
lab period.
This is one subsection of the main body of areport describing this whole lab.
Include an analysis of your results
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PreLab Requirements
Oscopes 2
Calculate the RC network resistor values
Review the Lissajous data
Comparators
Read the Op amp spec sheet, review the
troubleshooting guide.