Monday, October 12, 2009

Gavazzi Sensors Measure Environmental Variables

Carlo Gavazzi has introduced a range of sensors to measure environmental variables including CO2 levels, humidity, temperature and airflow. The CGES sensors complement the company's existing offerings to provide complete solutions for energy management, HVAC and smart building applications. The devices can be used to control humidity level in wet climates, improving comfort and discouraging the growth of mildew.

Standards introduced by the American Society of Heating, Refrigerating and Air-Conditioning Engineers define a maximum CO2 level of 1000ppm; and the ASHRAE 62-1989 norm has been widely adopted in countries including Sweden, France and Japan as well as the USA. CGESCO2 sensors use non-dispersive infrared (NDIR) technology to provide measurement ranges 0-2000 or 0-5000ppm.

Using an auto-calibration procedure to compensate for drift caused by ageing, the sensors are designed to provide traceable high accuracy and long-term stability. Operation in a closed-loop airstream avoids pollution of the CO2 sensor. Humidity measurements are based on a thin-film polymer, which releases or absorbs water vapour according to the ambient humidity, varying its dielectric properties accordingly.

The instruments' electronics measure the resulting change in capacitance, with excellent reproducibility that delivers accuracy of +/-3 per cent from 10 to 90 per cent RH. High-quality HC101 are said to guarantee excellent long-term stability and resistance to chemical pollutants. The air velocity sensors utilise the principles of thin-film anemometry, in which a heated resistive mesh is maintained at a constant temperature above that of the medium.

Air flowing over the resistor cools it and the power required to maintain the offset is used to determine air speed. Carlo Gavazzi's cutting-edge thin film technology gives accuracy over working ranges up to 20m/s. The sensor is insensitive to dust and dirt, and has low angular dependence. Measuring range and response time are selectable by jumpers.

Temperature measurement is available using Pt100, Pt1000, PTC or NTC resistance elements, ensuring typical accuracy of +/-0.3C at 20C. The sensors are available in duct or wall mounting formats and a switching output offers an alternative to the standard 0-10V DC voltage or 2-40mA current analogue outputs. Environmental sensors can be combined in wall- or duct-mounted units.

The CGESHTPD duct-mounted model features HC101 humidity sensors, combined with passive Pt100/Pt1000 temperature measurement, while the CGESCO2TW provides CO2, temperature and humidity functions in a room transmitter on the wall. The CGES range has traceability through international standards such as NIST, PTB and BEV. The sensors carry CE marks and are RoHS-compliant.

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