• Gas Sensing Technology at Speed

Air Monitoring

Gas Sensing Technology at Speed

Apr 22 2008

The response to the demand for more rapid, more reliable, measurement is leading to a shift away from what might be called the “conventional light bulb” to an LED light source. The miniature Indium Aluminium
Antimonide NDIR (LED) sensor from Air Monitors Limited (UK) is one of a new wave of sensors that delivers the benefits of this technology. Faster response, reduced power consumption, greater reliability and
repeatability are some of the advantages. The monitoring of Carbon Dioxide has been targeted to meet the broad applications of the marketplace. For example, the pending changes in the air conditioning systems used in the automotive industry require a method of being able to detect CO2 leakage from a highly pressurised systembefore the occupants are overpowered by the gas. This small sensor is perfectly suited to this application.
Developed by a partner, in Scotland, the sensor is derived from military technology and has been licensed for commercial use. The potential for the sensor was recently recognised with a place in the national final of the Shell (UK) “Springboard” competition for new, innovating businesses.
Our Technology: Air Monitors supply high performance Carbon Dioxide Sensors employing (Al-In-Sb) Indium Aluminium Antimonide technology on GalliumArsenide wafer substrate. The sensor can be supplied either as a standard RS232 output or adapted to meet customer applications.
The Carbon Dioxide measured output is temperature compensated and linearised.
This new solid state NDIR technology employs an LED and amatched Photodiode manufactured to operate within a narrow optical band centred on 4.26ìm. LED’s by nature are stable long life light emitters. The
optical housing employs a simple but efficient optical path that collects the emitted radiation on the photodiode.
The LED and Photodiode pair is mounted on a bridge PCB over a lensed mirrored reflector. The resultant high efficiency optical path transfers the emitted narrow band light at 4.26 micrometre from the LED through the gas to an adjacent Photodiode. The inherently
stable characteristics of this solid state technology, ensures reliable performance.
For higher specification and low cost systems alike this technology delivers, speed, low power consumption and stability.
For those wishing to evaluate the sensors for embedding in existing systems Air Monitors offer a development kit comprising a sensor and driver board, battery, or DC input, display, RS232 output (DB9 F), zero
function. The board outputs raw absorption, temperature index, concentration (ppmx10) four times every second.
When this technology ismatched with Air Monitors’ web logging system remote CO2 sensing becomes a cost effective option. Any location where concentrations of CO2 can have influence on activity or safety
can now be monitored.
For example: classrooms where drowsiness will affect learning: and outside where CO2 might be a marker to indicate the success of a climate change led traffic restriction scheme such as congestion
charging or park and ride.
Enquiries are welcome from manufacturers wishing to incorporate a high
performance sensor into a product and from end users who are looking for low cost, low maintenance method of measuring Carbon Dioxide. There are opportunities for customisation and partnerships to produce superior instruments and systems for Carbon Dioxide monitoring.

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