HDU and HDU-N transmitters are designed to detect carbon dioxide concentration and temperature inside the unheated spaces like parking halls.
The CO2 sensor will become self-calibrated regularly by using patented ABCLogic™ method. Outputs, linear 0-10V signals related to CO2-concentration and
temperature, can be used for demand controlled ventilation in buildings.

HDU-N is like HDU, but with a display. As a factory setting the display is scanning between temperature and CO2 every 2 seconds. By pressing the S1 button
inside the desired display mode can be selected. By changing the normal cover (and display) to the HDK-C option HDU (HDU-N) will become as a
controller.

ABCLogic™ & Calibration
ABCLogic™ is a patented self-calibration technique, that is designed to be used in applications where concentrations will drop to outside conditions (appr. 400 ppm) at least twice in a week period (= an unoccupied building). For applications that do not see periodic ambient conditions, ABCLogic™ can be turned off, but a regular single point calibration of the sensor in 6 -12 months is necessary. Checking and calibration is recommended every 5th year even if ABCLogic™ is on.