Sensors vs. Monitors vs. Probes vs. Checks

Comparing the terminologies of PRTG, WhatsUp, OpManager and SAM

Almost 20 years ago when I started my monitoring software company and wrote the first monitoring code (for “IPCheck” as it was called back then) I decided to use the word “sensor” as the name for the most basic monitoring item and the “probe” would be thing that gathered the data.

At about the same time people at Ipswitch, Solarwinds and ManageEngine had to make similar decisions, but they made different naming decisions that differenciate us to this day.


It is notable that all these four companies have about the same age.

  • Solarwinds: Founded in 1998.
  • Paessler: Founded in 1997.
  • ManageEngine: Founded in 1996.
  • IPSwitch: Founded in 1991.

We all share 20+ years of experience with monitoring literally millions of networks “on-site” and all are successful companies nowadays.

Here is an overview of the terms that each company uses today:

The Target System The thing that does the monitoring The thing that monitors one item
PRTG Network Monitor (Paessler) Device Probe Sensor
WhatsUp Gold (Ipswitch) Device Poller Active Monitor or Passive Monitor
Opmanager (Manageengine) Device Probe Monitor
Server & Application Monitor (Solarwinds) Node Agent Component Monitor

As you can see, we don’t agree on one set of words.

There are even more words out there, e.g.

  • Pingdom, a SaaS Monitoring service, calls it “Check
  • DataDog works with “Metrics” as well as
  • NewRelic, who calls them “Metrics“, too

These three are – as many others – much younger companies who do not offer LAN/network monitoring as the “Big Four” mentioned in my table above. They didn’t go through the long and tedious learning curve of having “boots code on the ground” at the customers’ sites with all the incompatibilities which are involved.

Do you know other companies that use other synonyms for sensors, probes and devices? Please share them in the comments!

PS: If you like how we think about IT and networks, check out our software PRTG Network Monitor which monitors uptime, usage and performance of networks.

Author: Dirk Paessler

CEO Carbon Drawdown Initiative -- VP Negative Emissions Platform -- Founder and Chairman Paessler AG