[Stoves] Gas Sensing

[Bear Kaufmann]

Hi all,

Jim Mason recently directed me to the discussion of gas sensing 
equipment on this list.
I've been working on developing a gas sensing system for our work with 
gasifiers.
The goal of the system is to provide real time data about the operation 
of the gasifier and to log the data to a computer (from gas sensor 
components, differential pressure gauge(s), and thermocouples).
The system consists of an Arduino USB microcontroller board 
(http://www.arduino.cc) along with electronics currently on a breadboard 
including 16 12-bit analog->digital channels, op-amp circuits, TC chip, etc.
The gas sensing components currently have all come from Figaro and are 
of two principal types: the electrolytic cells (Nernst) and 
semiconductor/metal oxide resistive types. I've currently interfaced an 
O2 and CO2 electrolytic cell (which requires some circuitry as mentioned 
before to amplify the very small voltage the cells produce). The 
resistive cells measure different gases that can be oxidized, including 
CH4, CO, mixed HCs, etc. The CO cell is $14.50, and does have some 
cross-sensitivity to methane. I haven't yet worked on calibrating these 
to known gas concentrations, which is of course an important next step. 
I'm also looking to source IR based sensors and interface them. The 
system requires dilution with air since the gas stream concentrations 
we'll be sampling are far above the 10,000 ppm limits of most of the 
resistive sensors, which is accomplished with a pump and two rotameters.

When searching for sensors to use in the system I developed a 
spreadsheet of sources that I could find online.
I've posted the spreadsheet on Google Docs, and it should be accessible 
with this link:
http://spreadsheets.google.com/ccc?key=pij8V7pu-JgwtzEMuyk78bg&inv=bear@ursine-design.com&t=4575016692417395121&guest 
<http://spreadsheets.google.com/ccc?key=pij8V7pu-JgwtzEMuyk78bg&inv=bear@ursine-design.com&t=4575016692417395121&guest>
Feel free to append this with other sources you may know of.
My main focus was on individual components, not on complete 
handheld/industrial systems (though the ITX system at the bottom may be 
of interest).

Hopefully the above information will be useful to others.
I can post further details of the system at a later date if others are 
interested.

Cheers,
Bear Kaufmann