Basic Elec. Engr Basic Elec. Engr. Lab . Lab ECS 204 ECS 204 - - PowerPoint PPT Presentation

• Asst. Prof. Dr. Prapun Suksompong

prapun@siit.tu.ac.th

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Basic Elec. Engr Basic Elec. Engr. Lab . Lab

ECS 204 ECS 204

Lab 2

• Thevenin’s and Norton’s Theorems
• New toy: Potentiometer
• Building a “fake” current source

Lab 2: Circuit under consideration

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(A.4)

Direct measurement

• f IL

Outline of the lab

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Part B (Norton Eq.) Part A (Thevenin Eq.)

Load resistor

Part A: Thevenin Equivalent (1)

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Part A (A.12) (A.13)

 

3 1 2 3 3 1 2

/ /

TH ps TH TH L TH L

R V V R R R R R R R V I R R        (A.14)

voltage divider

Part A: Thevenin Equivalent (2)

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Part A Directly measure VTH (A.5) and RTH (A.8) Build (Thevenin) equivalent circuit to measure IL (A.11)

V  Source(s) deactivated

Part B: Norton Equivalent (1)

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Part B (B.6)

1 2 N TH ps N N L N L N

R R V I R R R I I R R      (B.7)

Part B: Norton Equivalent (2)

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Part B Directly measure IN (B.2) Build (Norton) equivalent circuit to measure IL (B.5)

A

Note that the ammeter itself acts as a short circuit.

Lab 2: Summary

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Part B Part A (A.4) (A.14) (A.11) (B.7) (B.5)

Lab 2: Summary

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Part B Part A (A.4) (A.14) (A.11) (B.7) (B.5) Need resistor whose value can be adjusted arbitrarily Need current source

Potentiometer (Pot)

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Pot as a variable resistor

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 Manually adjustable resistor  Three terminals  The resistance between the middle terminal and either of the

two sides depends on the position of the wiper.

Current source

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 We do not have current source.

 Again, it is meaningless to connect an ammeter directly across

the power supply. This will NOT give you the amount of current produced by the power supply.

 We use a voltage source (power supply) to give the specified

amount of current.

IN

A

VPS IS pot