PRTG Manual: Modbus RTU Custom Sensor

Sensor creation

You can create this sensor only on a probe device.

IPv6

This sensor supports IPv6.

Performance impact

This sensor has a very low performance impact.

Lookups

This sensor uses lookups to determine the status values of one or more channels.

Serial port

This sensor always uses the serial port of the probe device.

Knowledge Base

Knowledge Base: How can I apply Zoom Service Status sensors and Modbus sensors via device templates?

Hosted probe

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.

Multi-platform probe

You can add this sensor to a multi-platform probe.

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

Enter a unit for the channel.

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

Channel #2 - #10

You can define up to 10 channels. You must define at least one channel, so you see all available settings for Channel #1. Specify how to handle all other possible channels:

• Disable (default): Do not create this channel.
• Enable: Create this channel. Specify at least the name, type, and register number for this channel below.

It is not possible to enable or disable channels after sensor creation.

Device COM Port

Enter the communication (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:

• None (default)
• Even
• Odd

Data Bits

Select the number of the data bits of the serial connection:

• 8 (default)
• 7
• 6
• 5

Stop Bits

Select the number of stop bits of the serial connection:

• 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:

• 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:

• 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 #x Scale Factor

If you want to scale the received data, enter an integer or a floating-point number. If you want to scale up, enter a value over one. If you want to scale down, enter a value below one. Use the default scale factor, 1, to not change the data.

Channel #1 - #10 Value Type

This setting is only visible if you select Input register or Holding register above.

Select the value type that the channel displays:

• 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 setting is only visible if you select Input register or Holding register above.

Select the data type of the register:

• 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 setting is only visible if you select Input register or Holding register above.

Select the width of the value in the register:

• 16 bits wide (default)
• 32 bits wide
• 64 bits wide

Channel #1 - #10 Bit Index

This setting is only visible if you select Input register or Holding register above.

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, PRTG displays the last value of the primary channel 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 this sensor shows different channels:

• 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 select Stack channels on top of each other above.

Select a unit from the list. PRTG stacks all channels with this unit 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 (default): Do not store the sensor result.
• Store result: Store the sensor result and the last response 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