Room unit with Rn CO2 PIR measurement - MIDAM RUI84011

Fuction

Communicative room sensor for temperature, relative humidity, radon, carbon dioxide and presence for easy sensing of these variables in rooms with variable or permanent occupancy. These values can be displayed to the user via a large LCD display. Communication via the open Modbus RTU protocol allows these controllers to be easily used and integrated into any open control system.The RUI84011 room sensor senses temperature, relative humidity, radon (Rn222) and CO2 concentrations. The sensed and entered values are sent to the RS485 bus. The variant with display allows data (heating/cooling mode, fan stage, day/night/attenuation mode) from the parent system to be sent back to the room controller display to allow a variety of options during project construction. A variant with backlit display or without display and rotary knob (see RUI84099) is also available. The radon concentration measurement range is 0...20000 Bq/m3. It is possible to set the concentration measurement in units of pCi/l. The device measures the radon activity in volume (VRA), radon decay products are filtered. The CO2 measurement range is 0...5000 ppm. A fraction of this value is converted using two parameters to a value of 0...100%, which is then shown on the display, e.g. 300...2500 ppm corresponds to 100...0% (air quality) or 0...100% (pollution). An absolute value in ppm is also available on the Modbus. The parameters are set using the configuration program supplied by the sensor manufacturer or by writing directly to the Modbus registers.The default values are 0%...350 ppm (clean air), 100%...2500 ppm (highest pollution). The device has factory set values to guarantee correct default operation and allows direct reading and writing of values to the Modbus map, which is available in a separate document. All settings are also stored in the modbus map directly in the device.

Application

• Control systems for HVAC (ventilation, heating and air conditioning) in rooms with variable or constant occupancy – offices, schools, theatres, lecture halls, residential buildings, etc.
• General monitoring of temperature, relative humidity, radon (Rn) and CO₂ in indoor environments.
• Integration into a supervisory control system (SCADA).

CO2 autocalibration function

Shocks during transport and aging can reduce the accuracy of the sensor. The sensor continuously monitors the minimum heading during operation and assumes that the CO2 level drops to the outdoor air concentration (350 ppm) at least once every 8 days. The lowest measured value is then assigned a concentration of 400 ppm. The autocalibration algorithm does not work if the room is occupied continuously or if there is no drop in concentration (e.g. greenhouses). In this case, the function can be invoked by a configuration program or switched off directly by writing to the modbus table. By default, autocalibration is switched on. During the first few days of operation, i.e. until the first autocalibration, the sensor may show values that differ by several hundred ppm from the actual values, e.g. about 200 ppm at night, etc. This is automatically corrected with the first self-calibration.

Configuration

The device is configured using a tool supplied by the manufacturer or a standard modbus tool that is capable of modifying the relevant registers. In this way, different operating modes can be configured. Modifications to the room unit configuration can be made later without the need for special tools such as setpoints, deactivating or enabling buttons, functions, etc.

Initial radon concentration values

The first measured values of Rn222 concentration are available after one hour of operation. To achieve maximum measurement accuracy, it is necessary to leave the device in operation for at least one week.

SCADA system integration

The room sensor can be integrated directly via the RS485 communication bus (Modbus RTU).