Sentera specialises in advanced control solutions designed to enhance HVAC system efficiency, comfort and air quality. With a strong global presence, Sentera offers a wide range of products including temperature, humidity, carbon dioxide, and air quality sensors, as well as controllers for fan speed control, air volume regulation, and HVAC system integration. As an industry standard, our products support the Modbus RTU communication protocol, ensuring seamless integration with building management systems (BMS). Committed to innovation and sustainability, Sentera invests in R&D to continuously improve its product range whilst providing extensive technical support to ensure customer satisfaction and optimal product performance.
General information
We integrated Modbus RTU in our products about a decade ago, but before that our products could be configured using jumpers and trimmers, i.e. manually. This was less accurate and also subject to mechanical malfunctioning or wear and tear.
In our recent products, we always have Modbus RTU communication available. It is now Sentera’s standard.
What is Modbus RTU?
Modbus RTU (Remote Terminal Unit) is a widely used protocol in HVAC systems for communication between controllers, sensors, actuators and other devices. Modbus RTU is known for its robust performance in industrial environments, ensuring reliable communication even in the presence of electrical noise.
Modbus RTU (Remote Terminal Unit) is a widely used protocol in HVAC systems for communication between controllers, sensors, actuators and other devices. Modbus RTU is known for its robust performance in industrial environments, ensuring reliable communication even in the presence of electrical noise.
The protocol supports multiple devices on a single communication bus, allowing for easy expansion of HVAC systems. Being a standardised protocol, Modbus RTU ensures that devices from different manufacturers can communicate seamlessly, promoting flexibility in system design.
The simplicity and widespread adoption of Modbus RTU make it a cost-effective solution for many HVAC applications.
Modbus RTU is an integral part of modern HVAC systems, enabling efficient and reliable communication between various components. It supports a wide range of applications, from simple temperature control to complex building management systems, enhancing the performance, efficiency and flexibility of HVAC operations.
So, in Sentera's environment, Modbus RTU is used for two primary purposes:
1. To integrate a device in a Modbus RTU network.
2. To configure a device.
Integrate a device in a Modbus RTU network
- A network is a combination of products that communicate with each other via a data signal
- Typical features of Modbus RTU:
- It is a serial communication protocol
- Each device has a unique Modbus ID
- There is 1 master and the rest of the devices are slaves
- The master reads information from the slaves (from the input registers)
- The master writes information to the slaves (to the holding registers)
- There is 1 master and the rest of the devices are slaves
- The master reads information from the slaves (from the input registers)
- The master writes information to the slaves (to the holding registers)
- Some Sentera devices have two Modbus channels:
- A Master channel for connecting the slaves
- A Slave (or Gateway) channel for connecting to a Master (e.g. SenteraWeb or a BMS – Building Management system)
- A Slave (or Gateway) channel for connecting to a Master (e.g. SenteraWeb or a BMS – Building Management system)
Not all data available on the Master channel is automatically available on the Slave channel. This needs to be “programmed” (i.e. needs to be in the unit firmware).
- By changing the firmware, a typical slave device (e.g. a sensor) can become a Master
- Some devices (the –M versions of Sentera’s sensors, such as RSMFM-3) have no analogue output. They cannot generate an output signal. They are meant to be part of a network.
- Others (the -H, -F and –G versions of Sentera’s sensors such as RSMFG-3) have an analogue output. They can work stand-alone, but they can also be part of a network.
Thus, the output signal of the RSMFG-3 can be controlled based on the measurements, which represents the stand-alone functionality. However, at the same time this signal can be read out by the network master (e.g. a BMS) and can even be overwritten by the network master (e.g. SenteraWeb scheduler)
Configure a device
A unit can be configured, no matter if it is supposed to be part of a network or to work stand-alone.
There are two types of Modbus registers:
a. Input registers contain actual values (e.g. measured values, output values, etc…) or settings. They are read-only.
There are two types of Modbus registers:
a. Input registers contain actual values (e.g. measured values, output values, etc…) or settings. They are read-only.
b. Holding registers contain settings. Most of them can be changed. They determine how the unit will function.
SENTERA’S MODBUS TOOLS
1. SenteraWeb
This is the preferred method for configuring a device or all devices within a network. It has a modern intuitive interface and all devices in the network can be configured using a standard browser, from any part of the world! All you will need is a Sentera Gateway (or a Sentera product with an integrated Gateway) as well as an internet access on site.
2. 3SModbus
This is free configuration software that can be downloaded from the Sentera Website. This tool is free, fast and intuitive, you only need a computer and Sentera's Modbus to USB converter.
3. Sensistant
The Sensistant is a hardware tool that can be used in the field to configure devices. It is a handheld device and you do not need anything else on site! It contains the Modbus input and holding registers and configures the Modbus RTU devices one by one.