Modbus Sensor Bridge

How to perform the web configuration of your Modbus Sensor Bridge

Julien Stamatakis avatar
Written by Julien Stamatakis
Updated over a week ago

Make sure you have properly installed your Modbus sensor bridge before continuing with the web configuration.


You can configure the Parity, Device Timeout, Endianness, and Baud Rate settings, as well as device operations, under the module configuration tab on the installations page

The default settings for the Modbus sensor bridge are as follows:

• Parity: No Parity with 1 Stop Bit
• Device Timeout: 250 ms
• Endianness: Little Endian
• Baud Rate: 9600

Reference the connected device's data sheet to configure the correct Senseware Modbus settings. You can set up conversion functions and conversion factors for each channel under the module configuration tab. The data is directly available via data forwards or the Senseware dashboard. You can also remotely reset the sensor bridge in the module information section of the system status by clicking on the 'Reset' button and selecting either 'Soft Reset' or 'Hard Reset.' A soft reset will restart the sensor and a hard reset will erase the saved configuration.

Read Operations

After visiting the module configuration tab scroll down to the section label Modbus Master, and begin configuring your Modbus read operation.

  1. Enter the address of the Modbus device from which you'd like to read. By default, operation 3 is selected (Read Holding Register). If you are reading a different type of data registers (Coil, Discrete Input, or Input Register) then select the relevant operation. 

  2. Select whether you would like to read a single register, or a range of registers, and whether those registers are 16 bit or 32 bit.

    Generally Modbus registers are 16 bit; if a field has the potential to store a large value (or floating point) it will be indicated as 2 consecutive registers, also considered a 32 bit register. The 32 bit option allows you to easily read from these registers without the need to configure a range.

    A range read will allow you to read all of the registers between two registers you define (inclusive), either as a range of 16 bit registers or 32 bit registers.

    The manual will indicate if a particular register or set of registers is floating point. If that is indicated, be sure to select 'Floating Point' from the Conversion Function dropdown menu.

  3. Click '+ Read another Register from this Device' to continue reading registers from the same Modbus device, or click 'Read From Modbus Device' to begin adding additional read operations for a new Modbus device.

  4. Once you have configured all of your read operations, click the Save button at the bottom of the page.

Deciphering Register Numbers

You will also need to enter the register number(s) you would like to read. These register numbers can be found in the manufacturer's datasheet or user manual for the device; sometimes a separate register map will be provided. Register numbers are provided one of two ways: either as a register offset, or as a register address.

Our system uses the register offset as the register number. If your data sheet begins numbering its registers with 0, 1000, or any other number ending in a 0, it likely also uses register offset. You can enter these numbers exactly as they appear.

If a register map lists registers starting at 1, 1001, or a number ending in 1, they likely use register address notation. To enter these registers into the Register Number field, simply subtract one from the register address listed in the manufacturer's manual.

Modbus Writes

Modbus writes allow you to perform commands, reset registers, and configure third party devices that communicate via the Modbus protocol. Writing via Modbus is very simple to do using our interface.

Before attempting to perform a write, make sure that your Modbus bridge is installed to an oulet-powered Node and connected to the network. We recommend configuring your Modbus bridge to read the register you will be writing to; this will allow you to confirm that the write was successful.

Initiating a Modbus Write

  1. After visiting the module configuration tab scroll down to the section label Modbus Master, and click the 'Modbus Write' tab to begin configuring your Modbus write operation.

  2. Enter the device address, register address, and value to which you wish you write. Make sure to use the Register offset and not the Register number. Please read the Deciphering Register Numbers section of the Modbus configuration page for more information.

    In most cases, you will not need to change the Modbus Function field or Data Type field. The datasheet for your Modbus device will indicate whether the relevant register is a holding register or coil as well as the data type.

3. Click on 'Write another Modbus Register' and repeat steps 1 and 2 for as many writes as you wish to perform on one device, up to 12 at one time.
4. Click 'Save' to send the write request to the Modbus bridge.
5. You can confirm that your write was successful by reading the register back from the device in the main System Status page, by clicking on the channel and verifying the read data point.

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