Digital Multi-meters

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Digital Multi-meters

• By Glen A. Mazur
• IMT 110

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Digital Multi-meters

• Electrical measurements are commonly taken using
  a digital multi-meter (DMM).
• This applies to residential, commercial and
  industrial electricity applications.
• Common sense dictates that proper safety
  precautions be taken when working on electric
  equipment and services.

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Digital Multi-meters

• Before working in the electrical field, you
  should know the safety rules and the proper first
  aid responses for working with and around
  electricity.

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Digital Multi-meters

• Know your meter and practice with it until you
  know how it functions.
• Keep it clean and in good repair.
• Check the leads often for breaks and damaged
  insulation.
• Always set the range to the highest setting to
  prevent damage to the DMM.

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Measuring AC Voltage

• AC voltage is the most common type of voltage
  used today.
• To read AC voltage
• 1. Set function switch to AC voltage. Set the
  range to the highest voltage setting.
• 2. Black lead goes in the common jack.
• 3. Red test lead goes in the voltage jack.
• 4. Connect the test leads to the circuit.
• 5. Read the voltage measurement displayed.

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Reading DC Voltage

• 1. Set the function switch to DC and the range to
  the highest setting.
• 2. Plug the black lead into the common jack.
• 3. Plug the red lead into the voltage jack.
• 4. Connect the test leads to the circuit. Black
  lead on the negative test point and the red lead
  on the positive test point.
• 5. Read the voltage displayed.

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Measuring Resistance

• Resistance measurements are taken to indicate the
  condition of a circuit or a component.
• The higher the resistance, the lower the current
  flow.
• Insulators would therefore have a very high
  resistance.

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Measuring Resistance

• 1. Turn the power off!!! (Check batteries in the
  DMM.)
• 2. Set function switch to resistance mode O.
  The display will indicate OL.
• 3. Black lead in the common jack.

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Measuring Resistance

• 4. Red lead to the resistance jack.
• 5. Connect the test leads across the component.
• 6. Read the resistance displayed on the DMM.
• 7. Shut off the DMM to save battery drain.

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Continuity

• Continuity is the presence of a complete pathway
  for current flow.
• Example a closed switch has continuity while an
  open switch does not.

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Continuity Testing

• Turn the power off and de-energize the equipment.
• 1. Set function switch to continuity (many
  testers the continuity and the resistance modes
  share the same function position).
• 2. Press the continuity button if required.

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Continuity Testing

• 3. Black lead to the common jack.
• 4. Red lead to the resistance jack.
• 5. Connect the test leads to the component.
• 6. If there is a complete current path the DMM
  will beep.
• 7. Turn the DMM off to prevent battery drain.

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The End!!!