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. 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. 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! Note: we have the same warning!

8 SEMICONDUCTORS We set the dial to “V” and then use the button to toggle to “DC”. 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. When measuring “AC”, select the “V” setting and your meter automatically defaults to AC voltage.

10 kk mAmVVA + V A  COM - d c a c Measuring Voltage Select the dcV function Connect - lead to - terminal of source Connect + lead to + terminal of source R 1 1 k  S 1 SPST B 1 15 V DC ELECTRICAL CIRCUITS

11 Measuring Current kk mAmVVA + V A  COM - d c a c Select the dc mA function R 1 1 k  S 1 SPST B 1 15 V DC ELECTRICAL CIRCUITS

12 R 1 1 k  S 1 SPST B 1 15 V kk mAmVVA + V A  COM - d c a c Select the dc mA function Physically interrupt the circuit Connect the - lead so that electrons enter it Connect the + lead to the other point Measuring Current DC ELECTRICAL CIRCUITS

13 Measuring Resistance  k  mAmVVA + V A  COM - d c a c Select the k  function R 1 1 k  S 1 SPST B 1 15 V DC ELECTRICAL CIRCUITS

14  k  mAmVVA + V A  COM - d c a c Select the k  function R 1 1 k  S 1 SPST B 1 15 V Remove power (open switch) Connect the leads Measuring Resistance DC ELECTRICAL CIRCUITS

15 Measurement Quiz Select the correct ____ of the meter before measuring an electrical quantity. When measuring voltage, the meter’s positive lead is connected to the ____ terminal of the source. When measuring current, the meter’s ____ lead receives electrons from the circuit. When measuring ____, the meter is connected to the points created by interrupting the circuit. Power is removed from the circuit before measuring ____. function positive negative current resistance DC ELECTRICAL CIRCUITS

16 Calculating Current I =I = VRVR = 36 V 1800  = 0.02 A = 20 mA S 1 SPST R 1.8 k  B 1 36 V DC ELECTRICAL CIRCUITS

17 Calculating Resistance R =R = V I V I = 24 V 0.03 A = 800  = 0.8 k  R B 1 24 V A 0.03 A DC ELECTRICAL CIRCUITS

18 Calculating Voltage V =V = IR = 0.15 A x 270   = 40.5 V R  B1B1 A 0.15 A DC ELECTRICAL CIRCUITS

19 Calculating Power P =  0.2 A IV =IV = 0.2 A x 54 V  = 10.8 W V 54 V P = I 2 R = 0.2 A x 0.2 A x 270  =10.8 W P = V 2 /R = (54 V x 54 V) / 270  = 10.8 W A DC ELECTRICAL CIRCUITS

20 Calculation Quiz Determine I when R = 10  and V = 25 V. Determine R when I = 1.3 A and V = 26 V. Determine V when R = 15  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 . Determine P when V = 8 V and R = 16 . 2.5 A 20  18 V 52.8 W 320 W 4 W DC ELECTRICAL CIRCUITS