This article applies to PRTG Network Monitor 13 or later

Short Answer

In PRTG "Sensors" are the basic monitoring elements. One sensor usually monitors one measured value in your network, e.g. the traffic of a switch port, the CPU load of a server, the free space of a disk drive.

On average you need about 5-10 sensors per server or one sensor per switch port.

All licenses of PRTG only differ by the maximum number of sensors that you can monitor (apart from this all licenses offer the same functionality), see the PRTG price list for details. BTW: When you a buy one license now you can upgrade to a larger one at any time by paying the price difference.

PRTG offers more than 200 sensor types (see: List of Available Sensor Types), each one counts as one "sensor".

More Detailed Answer

In PRTG you create "devices" which represent the actual devices in your network, and on those devices, you create "sensors".

About Devices and Sensors

• For example, create a device for your firewall, another for your Exchange server, and a third one which represents your printer.

• On each device you create one or more "sensors".

• Each sensor monitors one single aspect of a device. This can be, for example, a Ping time, the CPU load on a server, the traffic of a network interface, or the status of the toner cartridge.

Examples of Sensors

For example, when monitoring a firewall, an Exchange server, and a printer, you may use the following sensors.

* This is meant as an example only. It depends on your device and your network configuration which sensors can be used productively.

How Many Sensors Do I Need?

The number of sensors necessary for your individual setup depends on how closely you want to monitor your network. It is your decision whether you set up general Ping and Port monitoring for a device, or monitor it very closely, including many different performance parameters.

As a rule of thumb you can calculate with about 5 to 10 sensors per device.

What kind of Sensors are available?

There are more than 200 different sensor types available in PRTG. Please have a look at the List of Available Sensor Types. Monitoring one item from this list counts as one sensor.