Mailing List Archive

Mailing List: techdiver

Message Display

I've been getting a lot of email lately about how a person can make a 
miniox for cheap (actually how to use a voltmeter with an O2 sensor).

I don't have the original email sent to me on this subject anymore, 
however here's the jist of it.

Go and buy a Mini-Ox sensor (or any other sensor you like that will 
work with a miniox). Should cost you about $75-$85.

Go to Radio Shack. Buy a couple of stereophone miniture plugs. The 
type that will fit into the O2 sensor bottom.

Hook the sensor up to a voltmeter. Set the meter to DC, Millivolts. 
You may need to do some soldering to connect wires to the stereo plug.

Take out a calculator. Use a solar powered one to save batteries (and 
money).

Meter air. You should get a number like "11.7mv". negative or 
positive doesn't matter.

Take the O2 content of air (20.9) and divide it by 11.7. For those of 
you who are truly technical types take out the calculator, type 
"20.9" then the divide button then the mv on the sensor reading.

Now throw the sensor onto a tank of mix. You'll probably want some 
sort of flow regulator (you'll need one with a miniox anyway). Alex 
Varouxis makes this great little flow regulator that fits on top of a 
sensor and plugs into a power inflator hose, I think he sells them 
for $15. Of course you could buy the dive rite flow meter for $49 
which doesn't do half as much.

Let the sensor sit on the flow for a minute or so. Meter the sensor 
with the sensor still in the flow. Take the previous number (remember 
20.9/11.7) and multiply it by whatever the readout on your meter is 
now. That's your O2 content.

A few words of warning. Chemical sensors (such as Miniox sensors) are 
not 100% accurate. They're considered valid within 1-2%, so it may 
say "32%" when really it's 34% or 30%. This would be the case if you 
use a miniox as well. Also, these sensors will change calibration 
over time, and different temperatures as well, so you're an idiot if 
you don't calibrate your sensor before analyzing any tanks. The 
primary reason to analyze your tanks is for that "sanity check" to 
make sure you're within the ballpark. Obviously if you're expecting 
EAN 34% and your analysis says 50% you screwed up somewhere.

Credit for teaching me this goes to Bill Gavin. George Irvine hinted 
at it before hand, and Gavin went ahead and wrote it all up. It works 
great, I've been using it since Gavin explained the detail, and am 
quite happy that I haven't had to buy the miniox. Of course, buying a 
miniox would eliminate the mathwork, and for some the lack of the 
calculations will probably give them a warm fuzzy feeling.

Ken Sallot

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]