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Can a sensor be created for sudden drop in users?



I have a sensor that's currently showing total users logged into our systems. It shows 0 to as much as 8000 users logged in daily. I'm green to PRTG, so bear with me. I'm looking to find a way to utilize this sensor to show a drop of 1000 users within two minutes. So far, if I add a threshold trigger below a number, I will get an alarm every night when user access is low.

For example: If I have about 6000 users logged in, then within two minutes it drops to 5000 and stays at that, I'd like to receive an alert.

I have tried to find something with the unusual activity sensor, but i can't see a way to edit it.

I appreciate any help you can give. Many thanks!

sudden-drop timed-alert unusual user

Created on Oct 6, 2014 1:50:13 PM

3 Replies




Thank you very much for using PRTG. Unfortunately, it's not possible for a sensor (or a trigger on a sensor) to calculate the difference between the current and the last scan. May I ask, what kind is this sensor here?
There could be work-around of also checking the same information also with a script (running as a Custom Sensor. Where the script then calculates the difference between the current and the last scan, and returns this difference to PRTG. The alarming should then be done via the script sensor, and the other "normal" sensor could be used for normal reporting to see the average user numbers through the day / hours of the day.

best regards.

Created on Oct 8, 2014 12:42:23 PM by  Torsten Lindner [Paessler Support]



When you say 'I have a sensor', is that a Custom Sensor?

If so and asuming it is (or you can convert it to) a EXE/Script Advanced sensor, you can use the


html tag to report the difference between two scans instead of the absolute values.

Created on Oct 8, 2014 1:35:08 PM



Thank you both for replying and deepest apologies for replying so late. It has been a heck of a week at the office.

Again, forgive me for being new to PRTG...

The sensor was created before I took over the project.

From what I can tell it is a standard sensor (not a custom sensor) that counts totals of other channels to then produce a total count of all users that log into our host boxes.


I looked at the links that both of you suggested regarding the PRTG API. That MAY be a little out of my range as I'm not a programmer.

I really appreciate both of your responses. I will work on reviewing this option with an available programmer who has more experience.


Created on Oct 13, 2014 2:50:11 PM

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