Transcript Using a digital multimeter (DMM)

Using a digital multimeter
(DMM)
A brief guide
As a voltmeter (large voltages)
• Switch to V = 20, this
is the maximum DC
voltage it will read
• The red lead goes in
the V socket
• The black lead always
goes in the COM
socket
• Now you are ready to
measure voltage!
As an ammeter (large currents)
• Switch to 10A, this is the
maximum current that will
be read (wemay have to
change this later)
• The red lead goes in the
10ADC socket
• The black lead always
goes in the COM socket
• Now you are ready to
measure current!
As an ammeter (smaller currents)
• Switch to 20mA, this is
the maximum current that
will be read. If it says 2 its
2 mA
• The red lead goes in the
mA socket
• The black lead always
goes in the COM socket
• Now you are ready to
measure smaller
currents!
Measuring voltage
• Voltage is the potential
different between two
point in a circuit (how
much energy is carried by
each charge)
• Each charge gives up
energy as it travels
through a resistor
• So voltage must be
measured before and
after a component
Measuring voltage
• If you want to
measure the voltage
across resistor 2 you
have to connect the
voltmeter like this
• Don’t worry if you
geta –ve number, its
just connected the
wrong way round
Measuring current
• Current is the flow of
charge around a
circuit, the faster the
flow the higher the
current
• Current is the same
all around a series
circuit so place the
current anywhere
within the circuit to
measure the current
Measuring current
• Current is measure in
amps and the
ammeter has the A
symbol in a circle
• Don’t worry if you get
a –ve number, you
have connected it the
wrong way round.
• It doesn’t make any
different to the
number