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1
DC ELECTRICAL CIRCUITS
METER USAGE
2
INTRODUCTION
Students will be able to Measure
Electrical Quantities.
Students will be able to
Calculate Electrical Quantities
DC ELECTRICAL CIRCUITS
3
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.
4
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.
5
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”.
6
SEMICONDUCTORS
Notice the warning, DE-ENGERIZE CIRCUIT FIRST.
NO SOUND INDICATES AN OPEN CIRCUIT
7
SEMICONDUCTORS
Note: we have the same warning!
8
SEMICONDUCTORS
We set the dial to “V” and then use the button to toggle to “DC”.
9
SEMICONDUCTORS
When measuring “AC”, select the “V” setting and your meter automatically defaults to AC voltage.
10
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
11
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
12
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
13
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
14
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
15
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
16
Calculating Current
I =VR
= 36 V1800 W
= 0.02 A = 20 mA
S1
SPST
R
1.8 kW
B1
36 V
DC ELECTRICAL CIRCUITS
17
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
18
Calculating Voltage
V = IR = 0.15 A x 270 W = 40.5 V
R
270 W
B1
A0.15 A
DC ELECTRICAL CIRCUITS
19
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
20
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