PRTG Manual: Probe Health Sensor

The Probe Health sensor monitors internal PRTG parameters. It shows the state of the PRTG probe (either for the local probe, a remote probe, or a cluster probe). This sensor type is created automatically by PRTG and cannot be deleted. It checks various parameters of your PRTG system which can affect the quality of the monitoring results:

  • Health: This index value sums up the probe state into a value between 100% (healthy) and 0% (failing). Frequent or repeated health values below 100% should be investigated.
  • CPU Load: This channel shows the current percentage CPU load. Extensive CPU load can lead to false, incomplete, and incorrect monitoring results. This value usually should stay below 50%.
  • Handles: This is a counter for the data structures of the operating system. It is responsible for internal resource management. Repeated obviously increasing values should be investigated.
  • Interval Delay non-WMI&SNMP: This channel shows the percentage interval delay for all sensor types which are not from the type SNMP or WMI.
  • Interval Delay SNMP: This channel shows the percentage interval delay for SNMP sensors. If this value is above 0% there are probably very slow SNMP V3 sensors. In this case, try to increase the monitoring intervals or distribute the sensors over several probes.
  • Interval Delay WMI: This channel shows the percentage interval delay for WMI sensors. If this value is above 0% WMI sensors could not be checked according to their interval. 100% means that WMI sensors on the average are checked with twice their interval. For values above 0% try to increase the monitoring intervals or distribute the sensors over several probes to keep the number of WMI sensors per probe below 120 (with 60 seconds interval) or 600 (with 300 seconds interval).
  • Lost Flow Packets: This channel shows the percentage of lost flow packets.
  • Memory Usage: This channel shows the amount of memory being used by the PRTG probe service as reported by the memory manager. Repeated obviously increasing values should be investigated. If the value is constantly above 2 GB this indicates that PRTG runs at its limits. In this case you should distribute some sensors to Remote Probe.
  • Message Queue: This channel shows the number of monitoring results from the probe which have not been processed yet by the core. This value usually should stay below 1/10 of the sensor count.
  • Open Requests: This channel shows the number of currently active monitoring requests. This value should stay below the maximum of 500 open requests.
  • Threads: This channel shows the number of program parts which are running simultaneously currently. This value can increase with heavy load. The number should not exceed 100 in normal operation.

This sensor can be set up on a Probe Device only!

Sensor Settings

On the sensor's details page, click on the Settings tab to change settings.

Note: If not set explicitly in a sensor's settings, it will connect to the IP Address or DNS Name defined in the settings of the parent device the sensor is created on.

Basic Sensor Settings

Sensor Name

Enter a meaningful name to identify the sensor. The name will be shown by default in the device tree and in all alarms.


Enter one or more tags, separated by space or comma. You can use tags to group sensors and use tag-filtered views later on. Tags are not case sensitive. We recommend using the default value. You can add additional tags to it, if you like. Other tags are automatically inherited from objects further up in the device tree. Those are not visible here.


Select a priority for the sensor. This setting determines where the sensor will be placed in sensor lists. Top priority will be at the top of a list. You can choose from one star (low priority) to five stars (top priority).

Sensor Display

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel will always be displayed underneath the sensor's name. The available options depend on what channels are available for this sensor. Note: You can set another primary channel later by clicking on the pin symbol of a channel in the sensor's overview tab.

Chart Type

Define how different channels will be shown for this sensor.

  • Show channels independently (default): Show an own graph for each channel.
  • Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This will generate an easy-to-read graph which visualizes the different components of your total traffic. Note: This option cannot be used in combination with manual Vertical Axis Scaling (available in the Sensor Channels Settings settings).

Stack Unit

This setting is only available if stacked graphs are selected above. Choose a unit from the list. All channels with this unit will be stacked on top of each other. By default, you cannot exclude single channels from stacking, if they use the selected unit. However, there is an advanced procedure to do so.

Inherited Settings

By default, all following settings are inherited from objects higher in the hierarchy and should be changed there, if necessary. Often, best practice is to change them centrally in the Root group's settings. To change a setting for this object, disable inheritance by clicking on the check mark symbol in front of the respective setting name. You will then see the options described below.

Scanning Interval

Scanning Interval

The scanning interval determines the time the sensor waits between two scans. Select a scanning interval (seconds, minutes, or hours) from the list. You can change the available intervals in the system administration.

Access Rights

User Group Access

Define which user group(s) will have access to the object you're editing. A table with user groups and right is shown; it contains all user groups from your setup. For each user group you can choose from the following access rights:

  • Inherited: Use the settings of the parent object.
  • None: Users in this group cannot see or edit the object. The object does not show up in lists and in the device tree. Exception: If a child object is visible to the user, the object is visible in the device tree, though not accessible.
  • Read: Users in this group can see the object and review its monitoring results.
  • Write: Users in this group can see the object, review its monitoring results, and edit the object's settings. They cannot edit access rights settings.
  • Full: Users in this group can see the object, review its monitoring results, edit the object's settings, and edit access rights settings.

You can create new user groups in the System Administration—User Groups settings. To automatically set all objects further down in the hierarchy to inherit this object's access rights, set a check mark for the Revert children's access rights to inherited option.

For more details about access rights, please see section User Access Rights.

Channel Unit Configuration

Channel Unit Types

For each type of sensor channel, define the unit in which data is displayed. If defined on probe, group, or device level, these settings can be inherited to all sensors underneath. You can set units for the following channel types (if available):

  • Bandwidth
  • Memory
  • Disk
  • File
  • Custom

Note: Custom channel types can be set on sensor level only.

Edit Sensor Channels

In order to change display settings, spike filter, and limits, please switch to the sensor's Overview tab and click on the gear icon of a specific channel. For detailed information, please see Sensor Channels Settings section.


Click on the Notifications tab to change notification triggers. For detailed information, please see Sensor Notifications Settings section.


For more general information about settings, please see Object Settings section.

Sensor Settings Overview

For information about sensor settings, please see the following sections: