I wondered if I can create a scanning interval less than 30 seconds? If so how can I do that?

This article applies to PRTG Network Monitor 12 or later, as well as to previous (deprecated) versions

Important Note About Small Scanning Intervals

Yes, you can change the intervals. But...

Scanning sensors with intervals below 30 seconds usually does not give you more accuracy but causes unnecessary load on your machine and the network. Except for PING sensors— which only create minimal load —intervals below 30 seconds can cause problems and should be avoided.

Please use intervals below 30 seconds on a few selected sensors only. Especially WMI sensors should not scan with an interval smaller than 30 sec at all (for WMI the rule of thumb is: the longer the better).

Adjusting Scanning Intervals

In the PRTG web interface, go to Setup | System Administration | Monitoring ("System & Website" in previous versions), Scanning Intervals section.

Click in the list, and add your desired scanning intervals.

Note: In the deprecated PRTG version 7, the path is Setup | System Setup | Scanning Intervals.

Note for PING Sensors

Instead of pinging more often, increasing the number of pings per interval might give you more information. In the PING sensor settings, choose the Send multiple Ping requests and set the Ping Count to, e.g., 10. Instead of getting one value for each ping, you would get an average, max, min ping time, and packet loss then.