The Modbus RTU Custom sensor connects to a Modbus Remote Terminal Unit (RTU) server and monitors up to ten returned numeric values.
Modbus RTU Custom Sensor
For a detailed list and descriptions of the channels that this sensor can show, see section Channel List.
Sensor in Other Languages
Dutch: Modbus RTU Custom
French: Modbus RTU Custom
German: Modbus RTU Custom
Japanese: Modbus RTU Custom
Portuguese: Modbus RTU Custom
Russian: Modbus RTU Custom
Simplified Chinese: Modbus RTU Custom
Spanish: Modbus RTU Custom
Remarks
You can only create this sensor on a probe device, either a local probe device or a remote probe device.
This sensor supports the IPv6 protocol.
This sensor has a very low performance impact.
This sensor always uses the serial port of the probe device.
This sensor uses lookups to determine the status values of one or more channels. This means that possible states are defined in a lookup file. You can change the behavior of a channel by editing the lookup file that the channel uses. For details, see section Define Lookups.
You cannot add this sensor to the hosted probe of a PRTG Hosted Monitor instance. If you want to use this sensor, add it to a remote probe device.
Add Sensor
The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the settings that are required to create the sensor. You can change nearly all settings on the sensor's Settings tab after creation.
Modbus Channel Specific
Setting
Description
Channel #1 - #10 Name
Enter a name for the channel.
After sensor creation, you can change the name of the channel in the channel settings under Name.
Channel #1 - #10 Register Type
Select the type of the register. Choose between:
Coil (default): Coil numbers start with 0 and range from 00001 to 09999.
Discrete input: Discrete input numbers start with 1 and range from 10001 to 19999.
Input register: Input register numbers start with 3 and range from 30001 to 39999.
Holding register: Holding register numbers start with 4 and range from 40001 to 49999.
Input register bit: Select Input register bit to monitor a specific bit of the received value.Input register numbers start with 3 and range from 30001 to 39999.
Holding register bit: Select Holding register bit to monitor a specific bit of the received value. Holding register numbers start with 4 and range from 40001 to 49999.
It is not possible to change the register type after sensor creation.
Channel #1 - #10 Data Type
This field is only visible if you select Input register or Holding register above. Select the data type of the register. Choose between:
16-bit integer (default)
Unsigned 16-bit integer
32-bit integer
Unsigned 32-bit integer
64-bit integer
Float
Double
It is not possible to change the data type after sensor creation.
Channel #1 - #10 Unit
This field is only visible if you select Input register or Holding register under Channel #x Register Type. Enter a unit for the channel.
After sensor creation, you can change the unit of the channel in the channel settings under Unit.
Channel #2 - #10
You can create up to 10 different channels for this sensor. You must define at least one data channel, so you see all available settings for Channel #1 without manually enabling it. Additionally, you can define Channel #2 to Channel #10. To do so, choose between:
Disable (default): The sensor does not create this channel.
Enable: The sensor creates this channel. Specify at least the name, type, and register number for this channel below.
You cannot add additional channels after sensor creation.
Basic Sensor Settings
Click the Settings tab of a sensor to change its settings.
If the name contains angle brackets (<>), PRTG replaces them with braces ({}) for security reasons. For more information, see the Knowledge Base: What security features does PRTG include?
This setting is for your information only. You cannot change it.
Tags
Enter one or more tags. Confirm each tag with the Spacebar key, a comma, or the Enter key. You can use tags to group objects and use tag-filtered views later on. Tags are not case-sensitive. Tags are automatically inherited.
It is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).
For performance reasons, it can take some minutes until you can filter for new tags that you added.
The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:
modbus
Priority
Select a priority for the sensor. This setting determines the position of the sensor in lists. The highest priority is at the top of a list. Choose from the lowest priority () to the highest priority ().
Modbus RTU Specific
Modbus RTU Specific
Setting
Description
Device COM Port
Enter the component object model (COM) port of the serial port device.
On Windows systems, the COM port of the device looks like this, for example: COM3.
Baud Rate
Enter the speed of the serial connection in baud. The default baud rate is 9600.
Parity
Select the parity of the serial connection. Choose between:
None (default)
Even
Odd
Data Bits
Select the number of the data bits of the serial connection. Choose between:
8 (default)
7
6
5
Stop Bits
Select the number of stop bits of the serial connection. Choose between:
1 (default)
2
Retry Attempts
Enter the number of retries until a timeout occurs. If you enter 0, the sensor does not retry the communication attempt. The default value is 3. Enter an integer.
Receive Timeout (msec)
Enter a receive timeout in milliseconds (msec). If the reply from the device takes longer than this value, the request is aborted and triggers an error message. The default value is 500 msec (0.5 seconds).
Unit ID
Enter the Modbus unit ID that you want to monitor.
In a standard Modbus network, there are up to 247 unit IDs, each with a unique assigned identifier from 1 to 247.
Byte Order
Select the sequence of the transmitted information. Choose between:
Big-endian (AB CD)
Little-endian (DC BA)
Big-endian byte swap (BA DC)
Little-endian byte swap (CD AB)
Modbus Channel Specific
Modbus Channel Specific
Setting
Description
Channel #1 - #10 Register Type
Shows the register type of the channel value.
PRTG shows this value for reference purposes only. If you need to change this value, add the sensor anew.
Channel #1 - #10 Register Number
Enter the register number from which you want to retrieve information.
The register number must be a number that contains one to five digits. The sensor supports numbers between 0 and 65534.
Depending on your Modbus device, you may need to remove the register type prefix. For example, you need to enter 60 for the input register 30060 or 316 for the holding register 40316.
Channel #1 - #10 Value Type
This field is only visible if you select Input register or Holding register under Channel #x Register Type. Select the value type that the channel displays. Choose between:
Absolute (default): Integer64 values with or without an operational sign, such as 10 or 120 or -12 or 120.
Delta (counter): The sensor calculates the difference between the last value and the current value. The sensor additionally divides the delta value by a time period to indicate a speed value. The sensor ignores this setting if you select Double or Float as Channel #x Data Type. This mode only works if the difference between the last and the current value is positive and increases with each scanning interval. This mode does not support negative values and decreasing values.
Channel #1 - #10 Data Type
This field is only visible if you select Input register or Holding register under Channel #x Register Type. Shows the Data Type of the Register Number.
PRTG shows this value for reference purposes only. If you need to change this value, add the sensor anew.
Channel #1 - #10 Register Width
This field is only visible if you select Input register bitorHolding register bitunder Channel #x Register Type. Select the width of the value in the register. Choose between:
16 bits wide (default)
32 bits wide
64 bits wide
Channel #1 - #10 Bit Index
This field is only visible if you select Input registerorHolding registerunder Channel #x Register Type. Enter the index of the bit that you want to monitor.
Enter a value between 0 and 15, 31, or 63, depending on the Channel #1 - #10 Register Width. 0 monitors the least significant bit. To monitor the most significant bit, enter 15 for a 16-bit register, 31 for a 32-bit register, or 63 for a 64-bit register.
Sensor Display
Sensor Display
Setting
Description
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 is always displayed below the sensor's name. The available options depend on what channels are available for this sensor.
You can set a different primary channel later by clicking below a channel gauge on the sensor's Overview tab.
Graph Type
Define how different channels are shown for this sensor:
Show channels independently (default): Show a 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 generates a graph that visualizes the different components of your total traffic. You cannot use this option in combination with manual Vertical Axis Scaling (available in the channel settings).
Stack Unit
This setting is only visible if you enable Stack channels on top of each other as Graph Type. Select a unit from the list. All channels with this unit are 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.
Debug Options
Debug Options
Setting
Description
Result Handling
Define what PRTG does with the sensor result:
Discard result: Do not store the sensor result.
Store result: Store the last sensor result in the \Logs\sensors subfolder of the PRTG data directory on the probe system. The file name is Result of Sensor [ID].log. This setting is for debugging purposes. PRTG overwrites this file with each scanning interval.
This option is not available when the sensor runs on the hosted probe of a PRTG Hosted Monitor instance.
In a cluster, PRTG stores the result in the PRTG data directory of the master node.
Inherited Settings
By default, all of these settings are inherited from objects that are higher in the hierarchy. We recommend that you change them centrally in the root group settings if necessary. To change a setting for this object only, click under the corresponding setting name to disable the inheritance and to display its options.
For more information, see section Root Group Settings, section Scanning Interval.
Schedules, Dependencies, and Maintenance Window
You cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. The corresponding settings from the parent objects are always active. However, you can define additional schedules, dependencies, and maintenance windows. They are active at the same time as the parent objects' settings.
Schedules, Dependencies, and Maintenance Window
For more information, see section Root Group Settings, section Schedules, Dependencies, and Maintenance Window.
Access Rights
Access Rights
For more information, see section Root Group Settings, section Access Rights.
Channel Unit Configuration
Which channel units are available depends on the sensor type and the available parameters. If no configurable channels are available, this field shows No configurable channels.
Channel Unit Configuration
For more information, see section Root Group Settings, section Channel Unit Configuration.
Channel List
Which channels the sensor actually shows might depend on the target device, the available components, and the sensor setup.
Channel
Description
Downtime
In the channel table on the Overview tab, this channel never shows any values. PRTG uses this channel in graphs and reports to show the amount of time in which the sensor was in the Down status
[Value]
The returned numeric values in up to ten channels
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KNOWLEDGE BASE
How can I apply Zoom Service Status sensors and Modbus sensors via device templates?