# Introduction to the Multimeter - PowerPoint by VRX8nK

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DC Circuits Lab

ECE 002

George Washington University
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Objectives
 Constructing a Series Circuit
 Ohm’s Law Review
 DC Power Supply Review

 Measuring the D.C. Voltage in the Series Circuit
 Multimeter Overview

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Today we will build this series circuit
 Series Circuit From Lecture
I = ? Amps                     Determine the current

 Use Ohm’s Law:

3V       R = 1K Ω                     V      =I   x R

3V      =I   x 1000    Ω

Solve for I:

I=3V / 1000 Ω = 3milliAmps
0V

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How to Build the Circuit

I = 3mA                     We need 5 components
1) A 1K Ohm Resistor (Ask your
GTA for these materials)
3V      R = 1K Ω                    2) Breadboard
3) DC Voltage Source
4) 2 sets of Banana Clip to mini-
grabber wires

0V

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circuits quickly without the
need for soldering

 You can plug resistors and
wires right into the board

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 The 5 holes in each row are wired
 The rows themselves are not wired
together
 The rows do not connect over the bridge
BRIDGE

 The columns between the blue and
red bars are connected vertically
 We typically use these as ‘power rails’
 The left side we use for positive voltage
 The right side we use for negative voltage

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 Plug 1 end of the 1K resistor in the
top row, on the left side of the
bridge

 Plug the other end of the resistor
into the top row, on the right side of
the bridge

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Setting Up the DC Power Supply

 This DC Power supply is
capable of generating
voltages from -25V to 25V.

 For this lab, we will be
using the 6V supply
terminals.

 First, press the Power
Button to turn it on.

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Setting Up the DC Power Supply

 Press Output On/Off once to
turn on the output.

 Press the +6V button to tell
the power supply that we
want to alter the output
from the 6V terminals.

should look the same as it
does on this slide.

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Setting Up the DC Power Supply
Press this arrow to
 Use the dial to increase the          This is the digit         Select the
display value to 3 volts as          we want to adjust         desired digit
shown.

 Note: You can safely ignore
the value of the right most
digit for this experiment.

 Once you have reached 3V,
Press Output On/Off once to
turn the output OFF while
you hook up the circuit.
Rotate this dial to
alter the output value.

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Connecting the Power Supply to your
Circuit
 Plug the ‘banana’ end of
supply

 Connect the mini-grabber
ends of the cables around

 After attaching the mini-
press the Output On/Off to
apply 3 Volts across your 1K
resistor

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Measuring the Voltage Across the
Resistor…Using the Multimeter

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What is a Multimeter?
 A tool capable of measuring a variety of different quantities.

 Possible Measurements
 Current (Amperes)
 Resistance (Ohms)
 Voltage (Volts)

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How is the Multimeter different                                         14

than the Oscilloscope?
Multimeter                                     Oscilloscope
 Numerical Output Displayed              Graphical Output Displayed
 Represents a complete                   Shows how a signal changes
signal with a single value.              over time
 Measures voltage, current               Many only display voltage
and resistance.

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Explanation of Controls
Setting up the multimeter for various measurements.

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Taking measurements with the                                              16

Multimeter
First, we connect our wires.
 One wire is always
connected to the black
terminal. This is called the
common terminal.

 The red terminal is used
when measuring voltage,
resistance and small
currents.
TO DO: Using another set
 The white terminal is used
of banana to mini-grabber
when measuring large
currents.                                   cables, connect the
banana end to the red &
black terminals
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Taking measurements with the                                             17

Multimeter
 Next, we turn it on and select the item to measure.

 Choose from:                             TO DO: Since we want to
 Current                                measure the voltage
 Resistance                             across our 1K ohm resistor,
press the Voltage button
 Voltage

Power
Button

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Taking measurements with the                                              18

Multimeter
 Now, we select our scale.

 Either select a scale appropriate for your measurement or choose AUTO
and let the multimeter select the appropriate scale for you.

 Measuring the voltage from across the 1K resistor (~3V), you wouldn’t
want to choose 200mV (much too small) or 200V (much too large).
Instead, the 2V selection is more suitable.

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Taking measurements with the                        19

Multimeter
attached to the power
supply…

 Attach the minigrabber end
around the 1K resistor

 Press the “POWER” button
on the multimeter and take

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Building & Verifying Series Circuit #2
 Resistors connected by only
1 terminal, back-to-back,
R1 = 1KΩ                       are considered to be in
‘series’
 Ohm’s Law States:
3V     R2 = 1KΩ
V(R1) = 1.5mA x 1K Ω = 1.5V

V(R2) = 1.5mA x 1K Ω = 1.5V
 We are now going to build
the circuit, and verify the
0V                  voltage drops…

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 Turn off the 3V supply and disconnect
the cables

 Disconnect the cables to the
minigrabbers to the multimeter

 Obtain a 2nd 1K resistor
 Plug one end of the resistor into a
hole in the same row as the end of
the other resistor

 Plug the other end into a hole in
another rowUniversity
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Taking measurements with the                         22

Multimeter
 Set the Power Supply to 3V

 Attach the power supply

 Measure the voltage across
each resistor with the
multimeter

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Resistors in Parallel
 Resistors connected at 2
terminals, sharing the same
node on each side, are
considered to be in
‘parallel’
3V
 The voltage is the same on
both branches of the circuit

 The current will split!
R1 = 1K Ω R2 = 1K Ω
 It is now up to you to build
this circuit and verify the
0V                   voltages
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Including a Diode In the Circuit
 We’ll use LEDs (Light
Emitting Diodes) for our
circuits.

 Unlike resistors, the two diode
R1 = 1KΩ       connected in the correct way.
should be connect so that
current flows through it and to

0V
 Note: In some diodes, a stripe is used to indicate the cathode lead. Round diodes often have a
flat side, indicating the cathode.
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1) Build the parallel circuit (in slide 23) and measure the voltage
across each resistor
 Using Ohm’s Law, what is the current through each resistor?
 What is the total current in the circuit?

2) In your parallel circuit, change one of the 1K resistors to a 2K
resistor
 Measure the voltage across each resistor
 Use Ohm’s law to determine the current through each resistor

3) Build the two resistor series circuit (slide 20)…
   Swap the second of the 1K resistors for a 2K resistor
   Measure the voltage across each resistor
   Use Ohm’s law to determine the current through each resistor

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4) Build a circuit with a diode in series with a 1K resistor
 Using Ohm’s Law, what is the current through the resistor?
 What is the total current in the circuit?
 Reverse the anode and cathode connections of the diode and
observe the results.

5) Build a circuit with a diode in series with 2 parallel 1K resistors
 Measure the voltage across each resistor
 Use Ohm’s law to determine the current through each resistor