HD45 / HD46 series - RH, Temperature and CO2 Transmitters The instruments of the series HD45 and HD46 are transmitters, indicators and controllers, they measure and control, depending on the model, the following environmental parameters: • Relative humidity (RH) • Ambient temperature (T) • Carbon dioxide (CO2) • Dew point temperature (DP, calculated measurement) They are suitable for monitoring the air quality in indoor environments. Typical applications include checking air quality in all buildings occupied by people (schools, hospitals, auditoria, work places, canteens, etc.). This analysis allows the managing of conditioning plants (temperature and humidity) and ventilation (recycle air/hour) in order to reach a double purpose: getting a good air quality in accordance with ASHRAE and IMC regulations and energy saving. The measurement of RH (Relative Humidity) is obtained with a capacitive sensor. In models HD46 … the relative humidity and temperature sensor with their calibration data are contained within an easily replaceable module. The instrument can also calculate the information on the dew point. The temperature T is measured with a high precision NTC sensor. The measurement of CO2 (carbon dioxide) is obtained with a special infrared sensor (NDIR technology: Non-Dispersive Infrared Technology), which, by using a double filter and a particular measurement technique, ensures accurate measurements and stable measurements over time. The presence of a protective membrane, which is spread through the air portion, protects the sensor from dust and weather. The instrument can be wall mounted and sensors are internal to the instrument. The instruments are factory calibrated and require no further adjustment by the installer.