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Multimeter

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									Multi-Meters


Mr. Conrado
  Agm 243
Multi-meters
   Mr. Conrado
                  Digital Mult-imeter
• The digital multimeter is highly
  accurate and is used to find the
  precise value of any type of
  voltage, amperage, or resistance.
• The meter has four main areas:
   – the liquid crystal display
   – push buttons
   – rotary dial function switch
   – and inputs for the meter
      leads
        Liquid-Crystal-Display




• The LCD displays digital       •The analog display
  readings in 4000 count         is a 32 segment
  display with polarity          pointer that rolls
  indication and automatic       across indicating a
  decimal point placement.       measurement
  When turned on each            change.
  segment appears briefly as a
  self test.
                      Push Buttons
• The buttons are used to perform
  additional functions.
• The range button when pushed
  switches the meter from auto
  range to manual and displays
  the range scale to the right.
  Press and hold the range button
   to toggle back to auto range.
             Rotary Switch
• Various meter functions are selected by
  turning this switch.
              Meter Lead Inputs
• Depending on the measurement
  you wish to make, the meter
  leads must be placed in the
  correct terminals                       All other
                                          tests
                 Milliamps

                  Amperage




                                 Common
                      OL Display
• OL indicates that the value
  being measured is outside the
  limits of the selected range.
• Possible reasons for OL
    – In auto-range, a high
      resistance reading = Open
      Circuit.
    – In manual range a high
      resistance reading = open
      circuit OR incorrect scale
      selected.
    – Diode Check = voltage over
      3.0v or open leads.
               Measuring Voltage
• Leads must be connected to
  circuit in parallel.
• Circuit must be powered on.
• Black lead in the COM imput
• Red lead in the Volt / Ohm
  input.
• Rotary switch onto Voltage DC.
• Place black probe on ground of
  component or circuit.
• Red lead on the positive side of
  component or circuit.
• Ghost Voltage - If the reading
  will not lock onto a number that
  means you have an open circuit.
                      Voltage Drop
• Leads placed in parallel across
  circuit load.
• Voltage drop or total voltage
  drops should equal source
  voltage.
• If the voltage drop or drops is
  less than source voltage there is
  an unwanted resistance present
  in the circuit.
                Measuring Current
• When measuring current the
  meter leads must be connected
  in Series into the circuit.
• The meters red lead must also
  be moved to the Amperage or
  Milliamperage input.
• The Black lead stays in the
  COM input.
• Power up the circuit.
• If the current flow exceeds the
  rating of the fuse, the fuse will
  fail.
            Measuring Resistance
• When measuring resistance the
  circuit or component must be
  isolated from any power source.
• Be sure your hands are not touching
  the probes.
• The red lead is placed in the Ohm’s
  input
• The black lead is in the COM.
• Place the probes across the circuit
  or component to be tested
        Reading a Multi-Meter
• Multi-meter measurements are expressed in the
  metric system.
• Metric units are divided into factors of ten, you
  only need to multiply or divide in multiples of ten
  to obtain the desired unit.
• Meters have multiple scales/ranges. Each range
  starts at zero and has a maximum.
• Base Units - Standard units without a prefix.
  Volts, Amps and Ohm’s.
Multi-Meter Display
       Video

Multi-Meters Explained
Practice Exercises
Reading
Lab

								
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