Sigma (∑) column of particle counts

Particle counters display readings in two columns: cumulative (often depicted by ∑ sigma) and differential (often depicted by ∆ delta).

The cumulative total shows the amount of particles that were found at that size and greater.

The differential total shows the counts which are at least that size in diameter and up to, but not including the next size.

Looking for more information? Contact one of our cleanroom experts!

You may also find these arictles useful:

Last updated: 28 September 2023

We don’t just design and build high quality critical environments; our expertise extends into a comprehensive array of cleanroom services.

Our case studies demonstrate successful collaborations with clients across the globe!

I am looking for...