O2 + CO analyzer choices.

[JohnN]

There are 2 types of drift in an ElectroChemical sensor: zero reference (aka baseline) and span.
Your 0 ppm CO will be perfect to calibrate the baseline, but you will need something more than 0 to calibrate the span.

I'm pretty sure I understand two point calibrations (zero crossing and gain), but what is the difference with "calibrating" an O2 sensor in air?

 

[WarrenZ]

My only concern is COO is long form CO2 in my mind and since COOtwo runs together I might overlook that is is a combo device especially if it is listed in the same color text but I think that this is a great idea.

Maybe the New "DiveNav Gas Buddy O2+CO" or the "DiveNav Gas Check O2+CO"

Or if you want to keep with the whole brevity thing maybe reverse it as the "Otwo+CO" or "OtwoCO" Said "OH-two-co"

Not sure if any of those are trademarked yet.

---------- Post added June 5th, 2015 at 08:07 PM ----------

I'm pretty sure I understand two point calibrations (zero crossing and gain), but what is the difference with "calibrating" an O2 sensor in air?

The precision involved for a Parts Per Million reading is much tighter than for a fraction of O2

 

[JohnN]

The precision involved for a Parts Per Million reading is much tighter than for a fraction of O2

OK, but this looks like the "measure with a micrometer, mark with chalk and cut with an ax" paradigm. If 10 ppm is the max at 1 ATA, that says at 100' 3 ppm (@ 1 ATM) is the limit. Isn't any CO sufficient to reject the tank?

 

[WarrenZ]

My policy is if a tank reads 10PPM at the surface it gets dumped. I believe the Brits have a limit of 5PPM but that's a personal choice what standard you want to go with.

 

[tursiops]

I'm pretty sure I understand two point calibrations (zero crossing and gain), but what is the difference with "calibrating" an O2 sensor in air?

"air" is not always 20.9% O2, as read by an electrochemical analyzer. I'm in Bonaire right now, and with the heat and humidity you need to calibrate your analyzer to about 20.4 to get a good reading. See http://www.scubaboard.com/forums/ad...-oxygen-analyzer-post7376357.html#post7376357. There is a nice little table by Analox to show you what to do.

 

[DiveNav]

I'm pretty sure I understand two point calibrations (zero crossing and gain), but what is the difference with "calibrating" an O2 sensor in air?

Actually, when you are calibrating an Oxygen analyzer with ambient air you are indeed doing a 2 point calibration as the analyzer assumes the other point is 0 (plus whatever offset the analyzer might have built in) and then it draws an imaginary line (the reference line that you can see when using our Nitroxbuddy analyzer) between the 2 points.
While this is not the most correct (and the less accurate) way to calibrate an Oxygen analyzer, it is commonly done for mainly one reason: it is very easy to find the reference gas (Air)
Higher the percentage of O2 of the gas you want to analyze and higher the error will be.

 

[DiveNav]

I didn't see a link. Is the kickstarter up yet? DO WANT!

here you go --> cootwo: CO and O2 dual-gas analyzer for SCUBA divers. by DiveNav, Inc. — Kickstarter

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[JohnnyC]

Do I get something special for being the first backer?

Glad to see this on the market. I hope it reaches the goal ASAP.

 

[tursiops]

I just pledged to the Kickstarter campaign. I'm not anxious, but I did go out to the mailbox to see if it was there yet.....

 

[WarrenZ]

I'm backer #3 congrats on getting this one out.