Multimeter Categories

Testo 760 Category IV Multimeter

I was standing at a booth at the HVAC Excellence Educators conference, and an instructor walks up, grabs a meter, and asks me, “What's the difference between a category 3 and a category 4 meter?”

Well, I really wasn't sure, but I knew that the category 4 meter is rated for more demanding conditions. So, I did some research and dug into IEC 61010-1. I found that category 3 is rated for most uses OTHER than outdoor utility connections, and category 4 meters are rated for all uses.

Courtesy of Fluke

There are also some voltage considerations and limitations to the different categories, but the primary difference is not the regular duty but the high voltage transients. High voltage transients are often called “surges” or spikes and are most common when working on outdoor transformers and distribution panels.

Rubber meets the road because a category 3 meter is likely going to do the job for HVAC use. However, if you ever work in main panels or outdoor transformers, go for a cat 4 meter.

—Bryan

P.S. – Fluke has a great info sheet on this HERE.

You can see more about the Testo 760 shown HERE.

Related Tech Tips

Careful With Cleaners
When I was a green tech, I was really big into showing up all the other techs by doing THE BEST cleaning I possibly could. One of my favorite things to do was to clean the condenser until it was SPOTLESS inside and out. The only issue was that I really liked using that brown […]
Read more
5 Terror-Inducing HVAC/R Stories & Facts
As the evening approaches on this All Hallow's Eve, Reformation Day, or Halloween (depending on your preference), let us take a moment to focus on some of the truly terrifying elements of our trade—because the scariest stories are TRUE. Real Ghost Stories  The year was 1921, and a wealthy family purchased a new home in […]
Read more
Relative Humidity of Air Below Freezing
I was listening to someone talk about air relative humidity the other day while looking at a psychrometric chart, and he commented that the chart ends down at freezing (32°F) because “all the water freezes out of the air at that point.” I think I made this Jed Clampett face: The psychrometric chart is designed […]
Read more

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

loading

To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from