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Digital Multimeter Introduction
• Choosing the right meter Category
• Category ratings are designed to protect users from
transient overvoltage conditions (intermittent voltage
spikes caused by electrical equipment surges during
starting, capacitors, inductive circuits, and lightning
strikes)
• It is these unintended and intermittent transient voltage
spikes that can be dangerous to users with too low of
meter category rating
Digital Multimeter Introduction
• Choosing the right meter Category
1. With the likely hood of working in multiple different
category environments always choose a meter that will be
safe for working on the HIGHEST category that could
potentially be accessed
2. Choose a Steady State Voltage rating that meets the
maximum voltage you will encounter
3. ALWAYS choose the Category FIRST and then a steady
state voltage value
− A CAT III–600V meter will provide far superior transient
voltage protection than CAT II–1000V meter
Digital Multimeter Introduction
• Choosing the right meter Category
4. TEST LEADS: Be sure your test leads have an equal, or
HIGHER, Category and Voltage rating than the chosen
meter
– Meter system only as-good-as its components (as
strong as the weakest link)
– Quality Leads should be rated CATIII 1,000V and CAT IV
600 and UL Listed
– Double insulated
Digital Multimeter Introduction
4. TEST LEADS:
– Protective tips and accessory clips make connecting to
circuits and components easier and safer, but change the
category rating of the test leads.
• With Protective tips:
1000V CAT III & 600V
CAT IV
• WithOUT Protective
tips: 1000V CAT II &
600V CAT III (LOWER
Rating)
Review for Understanding
1. What are the two types of signals commonly converted
and displayed on a DMM?
2. True of False: DMMs can measure a wide range of
signals with accuracy.
3. How many ohms is 92.2 kΩ
4. Explain the 4 basic operations DMMs help us to perform.
5. Define High Impedance. Why is it important when
testing electronic circuits?