PRTG Manual: Modbus RTU Custom Sensor

Channel #1 - #10 Name

Enter a name for the channel.

You can change this value later in the channel settings of this sensor.

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.

You can change this value later in the channel settings of this sensor.

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.

Sensor Name

Enter a name to identify the sensor. By default, PRTG shows this name in the device tree, as well as in alarms, logs, notifications, reports, maps, libraries, and tickets.

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?

Parent Tags

The tags that the sensor inherits from its parent device, parent group, and parent probe.

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 ().

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)

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.

After sensor creation, this setting shows the register type of the channel value.

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 might 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 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

You cannot change this value after sensor creation.

Channel #1 - #10 Register Width

This field is only visible if you select Input register bit or Holding register bit under 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 register or Holding register under 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.

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.

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.

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