The series of transmitters HD37BT… and HD37VBT… are used mainly in air quality control by measuring CO2 (carbon dioxide) in the ventilation systems.
This allows you to vary the number of air change per hour according to ASHRAE
and IMC norms. The purpose is twofold: have a good air quality in the presence of people and save energy, increasing or decreasing parts of air per hour, depending on the air quality set.
Their use is for environments where there is overcrowding of people, discontinuous crowding, cafeterias, auditoriums, schools, hospitals, greenhouses, livestock breeding, etc.
The models HD377BT… and HD37V7BT… measure, in addition to CO2, also the temperature. The analog outputs, current 4…20mA or voltage 0…10Vdc, should be specifi ed when ordering.
All transmitters have an alarm digital output suitable to control, for example, an external relay coil. All transmitters have a digital alarm suitable to control, for example, an external relay coil.
The alarm is activated to pass a threshold set at the factory to 1500ppm, the threshold beyond which a man feels uncomfortable. The sensing element is made of a particular infrared sensor (NDIR technology: Non-Dispersive Infrared Technology) that compensates the effect of its aging thus ensuring accurate and stable measurements for a long time, by the use of a double fi lter and a articular measurement technique.The use of a protective membrane, through which the air to be analyze is diffused, minimizes the negative effect of atmospheric agents and dust on the performance of the transmitter.
A removable and washable fi lter is placed at the air fl ow transmitter inlet.
The installation methods may be:
• Wall mounted – TV Version,
• With power fl ow horizontally fi xed to the container, to be extent ventilation duct– TO Version,
• Wall outlet with fl ow separate with two tubes, connected to the electronics to the extent ventilation duet – TC Version,
In versions with power fl ow channel and separate electronics, the air is drawn into the measurement chamber. The same fl ow then returns to the channel through a second tube.
The air fl ow needs to be at least 1m/s. To fi x the air inlet to the duct, you can use the HD9008.31 fl ange, a 3/8” universal biconical fi tting or a PG16 metallic fairlead with a Ø 14 mm internal diameter. The air inlets connected to the transmitter by means of fl exible tubes are attached to the channels fl owing air: we supply air inlets for square or rectangular ducts (code HD3719) and for circular ducts (code HD3721). In order to maintain the specifi ed accuracy, the cable length should be 1m.