Transcript multimeter - Robotics Academy

MULTIMETER Introduction
• This PowerPoint is a companion
to the videos in “Background /
Resources / Multimeter Guide”
• It is recommended that you
watch the videos for an animated
explanation of this PowerPoint
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MULTIMETER Overview
In this presentation, you will learn:
• Continuity
• Using a multimeter to test continuity
• Reading direct current voltage using
a multimeter
• Reading the voltage of a battery
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MULTIMETER Continuity
• What is continuity?
– Defined as: uninterrupted connection
– The circuit below has continuity
– The circuit has an uninterrupted connection with the battery
Battery
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MULTIMETER Continuity continued
• If the wire is cut, the circuit no longer has continuity and the
light bulb is not lit
Missing
segment
of wire
Battery
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MULTIMETER Continuity Testing
How to perform a continuity test:
• Continuity testing is done with a
multimeter
• Allows a technician to see
whether or not a circuit is
complete
• Checking for continuity can help
you locate:
– Broken wires
– Defective switches
– Loose connections
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MULTIMETER Step 1
• Move the selector switch to
the continuity setting
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MULTIMETER Step 2
• Remove insulation from the
ends of a piece of wire
• Touch the multimeter test
probes to the wire, as shown
• If the wire is good, you will
hear a tone from the
multimeter, and the display
will show all zeros
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MULTIMETER Step 2 continued
• Note that polarity does
not matter
• If you switch the probes
of the multimeter, you
should still hear a tone
if the wire is good
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MULTIMETER Step 3
• Test the bumper switch by
building the setup to the right
• If you press the bumper switch,
you will hear a tone
• The tone means that the
bumper switch is working
• Repeat this set of steps for the
limit switch
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MULTIMETER Step 3 continued
• Note that you can directly
connect the probes to the
proper pins of the bumper
switch instead of using the
breadboard
• You will see the same results
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MULTIMETER Batteries and Continuity
• Continuity tests cannot be performed
on batteries
• If you try to perform a continuity test
on a battery, you will not harm the
meter, but you will get incorrect
readings
• Batteries should be removed before
testing the continuity of any device
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MULTIMETER Practice
• You can try continuity tests on:
– Switches
– Wires
– Cables
– Flashlight bulbs
• This will give you more
experience with continuity
testing
Battery
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MULTIMETER DC Voltage Testing
• What is DC Voltage testing?
– Reading the voltage of circuit
elements, such as batteries and
cells
• Why is this useful?
– Weak or dead batteries will
render your electronic device
useless
– DC voltage testing is a good first
step in troubleshooting
For more information on direct or
alternating current, refer to “Overview /
Guides / Note to the Student”
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MULTIMETER Step 1
How to read DC voltage:
• Insert the red test wire into the red
jack, as shown
• Do the same for the black wire
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MULTIMETER Step 2
• Rotate the multimeter’s selector
switch to DC Volts
• The multimeter is now ready to
read voltage from a device
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MULTIMETER Step 3
• Touch the multimeter probes to the ends
of a AA battery
• Standard voltage for AA batteries is 1.5 V
• Does your display show this?
• What happens when you switch the
multimeter probes?
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MULTIMETER Step 3 continued
• If you switch the probes,
your voltage reading will
become negative
• What is polarity?
– Having two oppositely
charged poles, one
positive and one negative
– Batteries have polarity
– On a multimeter:
• The black probe is
negative
• The red probe is positive
Multimeter Reading:
-
Battery
1.5 V
+
Negative probe
Positive probe
Multimeter Reading:
Positive probe
Battery
- 1.5 V
+
Negative probe
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MULTIMETER Step 4
• Touch the probes of the
multimeter to a 7.2 V battery
• Do this by connecting the probe
tips to the connector pins inside
the plug as shown
• What is the multimeter’s reading?
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MULTIMETER Step 5
• Remove the batteries
from your radio control
transmitter
• Lay them out end to
end, as shown
• Make sure the
negative terminals only
touch positive
terminals
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MULTIMETER Step 5 continued
• Connect the meter as
shown
• Make sure that the red
probe is touching the
positive terminal of the
top battery
• Make sure that the black
probe is touching the
negative terminal of the
bottom battery
• What is the total voltage of
these 8 batteries?
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MULTIMETER Step 5 continued
• When batteries are
connected together like
below, their voltages add
together
• These batteries are “in
series”
Voltage of 1 AA battery = 1.5 V
Number of AA batteries = 8
Total voltage of 8 AA batteries in series:
1.5 V + 1.5 V + 1.5 V + 1.5 V + 1.5 V + 1.5 V + 1.5 V + 1.5 V = 12 V
1.5 V x 8 = 12 V
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MULTIMETER Step 6
• Place the batteries back in
the radio control transmitter
• Place the probes as shown
• Observe the voltage reading
• What do you expect it to be?
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MULTIMETER Step 6 continued
• Now, place the probes differently,
as shown at right
• What voltage reading did you get?
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MULTIMETER Step 6 continued
• Continue to move the
black test probe, as shown
• Do the values you read
from the multimeter make
sense?
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