S+S Regeltechnik AERASGARD RFTM-LQ-PS-CO2-MODBUS Notice D'instruction page 16

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AERASGARD ® RFTM - LQ - PS - CO2 - Modbus
Rev. 2021 - V30
ATTENTION !
The minimum CO2 concentration of outdoor air amounts to approx. 350 ppm in leafy, hardly industrialised areas. Gas inter-exchange in the sensor
element happens by diffusion. Depending on the changes to the concentration and the flow velocity of the air surrounding the sensor, the reaction of
the device to the change of concentration may take place with a delay. It is essential to choose an installation location for the device in which the air
stream flows around the sensor. Otherwise the gas exchange may be considerably delayed or prevented.
Automatic calibration of the carbon dioxide measurement (default)
The automatic background logic is a self-calibrating mechanism that is suitable for use in applications in which the CO2 concentration drops to fresh
air level (350 - 400 ppm) at least three times in 7 days. This should typically occur during times in which rooms are unoccupied. The sensor reaches
its normal accuracy after 24 hours of continuous operation in an environment that has been subjected to a fresh air supply of 400 ppm CO2. The
deviation errors remain minimal if the sensor is exposed to fresh air at least 4 times within 21 days. The device needs continuous operating cycles
of more than 24 hours to operate correctly. Automatic zero point calibration is deactivated by default in the as-delivered condition and, if required,
must be activated using the Modbus.
Manual calibration of carbon dioxide measurement
Manual calibration can be carried out independently of the DIP switch position.
Sufficient fresh air (CO2 content = 500 ppm) must be provided before and after the calibration procedure!
The calibration procedure is started by pressing the "ZERO CO2" (for approx. five seconds).
This is signalled by the flashing LED or the countdown timer on the display (AUTO 0).
Then calibration takes place.
During this phase, the LED is constantly active and a 600-second countdown runs on the display CAL 0).
The LED is deactivated after successful calibration.
Automatic air quality calibration (permanently active)
We recommend to rinse the sensor every 7 days for 20 minutes or longer with fresh air as a basis for automatic calibration.
Within a period of approx. 3 weeks, the minimum output value for air quality is saved. During this period, the output signal is standardised to the zero
point. The maximum correction per interval is limited here. Long-term drifts and the operation-related ageing of the sensor element are thus
completely eliminated.
Every time the device is switched on, the automatic calibration cycle restarts and calculates a correction value across the operating period.
In case of power disruptions of less than 7 days, the calculation algorithm may be supported with a manual calibration to adjust the correction value
more quickly.
Manual calibration of air quality
Manual calibration can be carried out independently of the DIP switch position.
Sufficient fresh air must be provided before and after the calibration procedure!
We recommend a fresh air supply of at least two hours before the calibration process.
The calibration procedure is started by pressing the "ZERO VOC" button (for approx. five seconds).
This is signalled by the flashing LED or the countdown timer on the display (AUTO 0).
Then calibration takes place. During this phase, the LED is constantly active and a 60-second countdown
runs on the display CAL 0). The LED is deactivated after successful calibration.
General information on air quality
The service life of the sensor depends on its functional principle and the type and concentration of pollutant gas burden. The sensitive layer of the
sensor element reacts with all volatile organic compounds and is therefore modified in its electrical properties. This procedure leads to an offset of
the characteristic line. When measuring the air quality, the general condition of the air quality is recorded. Whether the air quality is "good" or "bad"
depends on the individual interpretation of each individual. Different pollution burdens and concentrations influence the air quality signal (0 - 10 V) in
different ways. Examples are cigarette smoke, deodorant sprays, cleaning agents and various adhesive materials for floor and wall coverings, as well
as dyes. Increased levels of solvents, nicotine, hydrocarbons, aerosol propellants, etc. intensify the wear/ageing of the sensor element. Especially at
high pollutant gas burdens, even when the devices are idle (transport and storage) the zero point is adjusted. This must be corrected on-site
depending on the specific conditions or basic burdens. Air quality measuring instruments from various manufacturers cannot be compared directly
with each other because of the different functional principles, the pre-set basic burden (zero point) and the permitted burden (amplification/sensitivity).
The devices are set or calibrated according to the specifications of the sensor manufacturer. Here, a zero point and end value, and therefore a
maximum load, are established. In special circumstances, there is an overrun of the measuring range or an excessively high basic burden on the
devices (out gassing carpets, wall paint, etc.) In order to enable a measurement or distinction of different air qualities, the devices must be configured
by the client in accordance with the on-site conditions which do not correspond to the function domain and thus the factory calibration. Here, it
should be noted that the factory calibration will be lost and technical data compliance can no longer be guaranteed.
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