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DC ELECTRICAL CIRCUITS

METER USAGE

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INTRODUCTION

Students will be able to Measure

Electrical Quantities.

Students will be able to

Calculate Electrical Quantities

DC ELECTRICAL CIRCUITS

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SEMICONDUCTORS

You will need to be familiar with the basics of your digital multi-meter to successfully test the different components you will be using in your experiments.

The most basic test is a continuity test using the ohms scale typically set to RX-1 or Ω.

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SEMICONDUCTORS

Some meters have a chime indicator for continuity tests.Here we are testing our meter by touching the leads together, we should have a very low resistance (only the resistance of the test leads is indicated.

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SEMICONDUCTORS

If we get an “OL” reading something is wrong, OL stands for “open loop” or infinite resistance, it may be necessary to check the fuse if you read “OL”.

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SEMICONDUCTORS

Notice the warning, DE-ENGERIZE CIRCUIT FIRST.

NO SOUND INDICATES AN OPEN CIRCUIT

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SEMICONDUCTORS

Note: we have the same warning!

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SEMICONDUCTORS

We set the dial to “V” and then use the button to toggle to “DC”.

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SEMICONDUCTORS

When measuring “AC”, select the “V” setting and your meter automatically defaults to AC voltage.

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kW W mAmV V A

+ V A W COM - d c a c

Measuring Voltage

Select the dcV function

Connect - lead to - terminal of source

Connect + lead to + terminal of source

R1

1 kW

S1

SPSTB1

15 V

DC ELECTRICAL CIRCUITS

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Measuring Current

kW W mAmV V A

+ V A W COM - d c a c

Select the dc mA function

R1

1 kW

S1

SPSTB1

15 V

DC ELECTRICAL CIRCUITS

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R1

1 kW

S1

SPSTB1

15 V

kW W mAmV V A

+ V A W COM - d c a c

Select the dc mA function

Physicallyinterrupt the circuit

Connect the - lead so that electrons enter it

Connect the + lead to the other point

Measuring CurrentDC ELECTRICAL CIRCUITS

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Measuring Resistance

kW W mAmV V A

+ V A W COM - d c a c

Select the k Wfunction

R1

1 kW

S1

SPSTB1

15 V

DC ELECTRICAL CIRCUITS

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kW W mAmV V A

+ V A W COM - d c a c

Select the k Wfunction

R1

1 kW

S1

SPSTB1

15 V

Remove power(open switch)

Connect the leads

Measuring ResistanceDC ELECTRICAL CIRCUITS

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Measurement QuizSelect the correct ____ of the meter before measuring an electrical quantity.

When measuring voltage, the meter’s positive leadis connected to the ____ terminal of the source.

When measuring current, the meter’s ____ leadreceives electrons from the circuit.

When measuring ____, the meter is connected tothe points created by interrupting the circuit.

Power is removed from the circuit beforemeasuring ____.

function

positive

negative

current

resistance

DC ELECTRICAL CIRCUITS

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Calculating Current

I =VR

= 36 V1800 W

= 0.02 A = 20 mA

S1

SPST

R

1.8 kW

B1

36 V

DC ELECTRICAL CIRCUITS

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Calculating Resistance

R = V I =

24 V 0.03 A

= 800 W = 0.8 k W

R

B1

24 V

A0.03 A

DC ELECTRICAL CIRCUITS

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Calculating Voltage

V = IR = 0.15 A x 270 W = 40.5 V

R

270 W

B1

A0.15 A

DC ELECTRICAL CIRCUITS

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Calculating Power

P =270 W

0.2 A

IV = 0.2 A x 54 V = 10.8 W

V54 V

P = I2R = 0.2 A x 0.2 A x 270 W = 10.8 W

P = V2/R = (54 V x 54 V) / 270 W = 10.8 W

A

DC ELECTRICAL CIRCUITS

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Calculation QuizDetermine I when R = 10 W and V = 25 V.

Determine R when I = 1.3 A and V = 26 V.

Determine V when R = 15 W and I = 1.2 A.

Determine P when I = 3.3 A and V = 16 V.

Determine P when I = 4 A and R = 20 W.

Determine P when V = 8 V and R = 16 W.

2.5 A

20 W

18 V

52.8 W

320 W

4 W

DC ELECTRICAL CIRCUITS