Indoor air quality sensor - RLW-THC

Product description

Unipi indoor air quality sensors are designed for measuring indoor air quality in office buildings, schools, factory halls, and other similar objects. Sensors can be used to measure temperature, relative air humidity, barometric pressure, volatile organic compound concentration, and ambient light intensity. Selected variants are also equipped with a carbon dioxide (CO₂) concentration sensor. Due to the RS485 and WiFi interfaces, wide connectivity is ensured. In addition, selected variants also have an interface for LoRaWAN wireless technology.

Available model overview

Hardware description

The sensor’s circuit board is mounted in a compact design box (IP20 protection) intended for indoor on-wall installation. The box is designed for easy access to the sensor board itself. The sensor features a terminal block for connection of power supply and RS485 bus, and also a MicroUSB power supply connector. 

The sensor can be powered in two ways:

1. 24 V⎓/0,5A power supply connected to the sensor's terminal block
2. 5 V voltage via a USB power cable with long MicroUSB connector (regular USB cables with short MicroUSB connector cannot be used to power Unipi indoor air quality sensors)

Note: The power supply and the USB cable are not included in the package and have to be purchased separately. 

The sensor is also equipped with a multi-colored LED. For models featuring a CO₂ sensor, the LED indicates carbon dioxide concentration (green = low concentration, red = high concentration). For variants lacking the CO₂ functionality, the LED then indicates an air quality index roughly equivalent to CO₂ concentration. In all models, the LED has a secondary function of indicating wireless communication and device status. 

Users can also adjust the LED’s brightness or turn it off entirely. Brightness adjustments and on/off switching can be also controlled automatically by a pre-set time schedule or ambient light intensity. In hotel rooms or bedrooms, for example, the LED can be configured to turn off along with the room’s light to prevent sleep disturbance by the LED’s light. 

User interface

Sensors are provided with a web user interface for displaying measured values and device management including remote firmware updates. A particularly useful feature is the option to store all measured values for up to 7 days. Values can be displayed directly in the interface or exported as an Excel file (CSV).

Communication interface

The primary communication interface of indoor air quality sensors is a wireless Wi-Fi connection. For initial configuration, the device acts as a Wi-Fi access point. For regular usage, the sensor then switches to Wi-Fi client mode. Wi-Fi interface supports communication via Modbus TCP, MQTT (including encoded connection support), and REST API. 

The second interface is the RS485 standard serial bus for communication via Modbus RTU. The sensor functions as a Modbus slave, serial line, and TCP parameters can be configured as needed. 

Selected variants also feature wireless communication using the LoRaWAN technology, combining long signal range (up to several kilometers), low energy consumption, and an option of bidirectional communication. Users can create private networks or utilize commercial networks provided by mobile operators. 

Note: To use LoRaWAN you need to register the sensor at the public operator or in a database of a private LoRaWAN gateway. Unipi technology currently does not offer LoRaWAN gateways.

Software options

The indoor air quality sensors are supported in the Mervis system- an officially supported software solution for Unipi programmable logic controllers. As sensors function as Modbus devices, all you need to do to connect them into the Mervis IDE development environment is to add a corresponding communication channel and detect the sensor on it. More information about Mervis is available on this link.

Aside from Mervis, the sensors can be connected to other software solutions (ie. third-party software such as Node-RED or custom solutions) using any of the available communication interfaces (see above).

Possible applications

Aside from air quality monitoring in households, commercial objects, or school buildings the sensors can be also useful in monitoring and regulation projects. Here, you can use measured values for control and regulation of air conditioning, heating, heat recovery units, and other similar devices.

Further info

• learn more about Unipi indoor air quality sensors
• more about the Mervis system
• Unipi Knowledge Base