Gas Sensors

efrag

Hello,
I want to make a system that checks the quality of the air inside a classroom. I'm planning to use Parallax Gas Sensors
www.parallax.com/Store/Sensors/GasSensors/tabid/843/List/0/CategoryID/91/Level/a/SortField/0/Default.aspx
I will take readings during the class hours, and I will display them on a LCD display, and also I will transmit them to a PC near the classroom.
The question I have is: if the Gas Sensor Module (CO,CO2 or LPG) is able to take continues readings or they just send a signal if an alarm condition is take place? and if they can, how can I read them.

If there are any other ideas please post

Thanks

Adrian Schneider

From what I read in the Parallax odcumentation you should be able to get a continuous sensor reading from TP1 and TP2 using a separate AD converter (LTC1298 or so).
I suppose you intend to use different sensors to distinguish different gasses with their individual concentrations. This was also my idea. After reading the spec sheets of these sensors I concluded that each sensor is more or less sensitive to all the gasses (CH4, CO, LPG), just with an individual preponderance for one. Thus the sensor reading always represents a concentration of a mixture of those gasses (and maybe others) and does not allow to distinguish between them.

Regards
Adrian