D4.3 - Application of Micro- and Nanotechnologies for NDIR-Gas Measurements in Harsh Environments

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
D4 - Gas Sensors II
R. Buchner, T. Stolberg-Rohr, K. Pihl, J. Hansen, S. Trojaga, A. Krishna, H. Moos, J. Jensen - Danfoss IXA A/S, Vejle (Denmark)
583 - 588


A new infrared gas sensor technology for measurement of relevant parameters for climate and emission control has been developed, such as temperature, humidity, CO2, NOx and other gasses in harsh environments and as close to the source of emission as possible. Exact determination of these parameters improves climate and process control leads to significant energy savings and reduction of emission.
By combining highly sensitive thin-film thermopiles with fast MEMS-based infrared sources and specific IR-optical components, determination of these parameters is possible in environments where other systems fail due to e.g. contamination and corrosion. Functionality of the sensor system has been proven and criteria for proper choice of the MEMS components are given.
The NDIR-gas sensor system developed incorporates two major innovations. One is the new and patented IR-filter configuration that makes it less sensible towards changes in ambient temperature. The second innovation is the protected open-path concept that allows measurement of corrosive gasses while protecting the components from any impact by special IR-optical windows.
A MEMS based emitter is providing infrared radiation that is partly absorbed by the gas, spectrally filtered and detected by a multi-channel thin-film thermopile. MEMS technologies and the performance of MEMS components can be seen as enabler for this gas-sensing technology. First miniaturized thin-film thermopiles have been presented in the 80s and IRradiation measurements have been the driving application.
Today this technology is used in flow measurement, for dew point sensors, and in a lot of other applications. The variety of infrared emitters is somewhat smaller than of the thermopiles but still there are different technological approaches for different applications. The miniaturization of this component allows direct modulation due to the small thermal capacity and reduces the energy consumption. Hand in hand with the improvements due to miniaturization goes the increased susceptibility towards environmental changes e.g. could we investigate a severe impact of the humidity and the increased thermal conductivity on the emitter’s temperature as well as a dependency of the systems orientation in non modulated mode.
Our application area and the harsh environments require careful investigation on the components down to the chip and technology level in order achieve a system durable under shock, vibration, elevated humidity as well as exposed to aggressive chemicals and still taking the cost structure of the system into consideration. The careful choice of components and the system setup lead to a sensor whose functionality has been proven on the measurement of CO2 and humidity under severe vibration, wide temperature range and chemical aggressive environment.