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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.