CooTwo - CO reading inconsistent based on ambient temperature

[Got2Go]

Hello,

I purchased a new CooTwo a couple of months ago (April), and I have yet to be able to get a reliable CO reading from it.

It seems the CO reading varies greatly based on ambient temperature.
I have already sent it back to DveNav at my expense, and they sent it back saying they calibrated it and it was good to go.
But, when I tried to use it for the first time(about a week ago) after receiving it back, as soon as I turned it on, the CO was reading very high and flashing.

I did an experiment to try illustrate the issue.

1- I placed the CooTwo in a ziplock bag, along with a thermometer, and simply turned it on when indoors at A/C room temperature and took a pic of the reading.

Photo showing 75.2F temp and 0.3 CO


2- Then I placed it outside and let it acclimate to outside temperature, turned it on, and took another picture.
All of this without opening the zip lock bag.

Photo showing 102.0F temp and 8.9 CO


3- And lastly, I brought it back inside, let it acclimate to indoor A/C room temperature, and turned it on.

Photo showing 75.7F temp and 3.1 CO


It seems to me that the CO reading is not reliable for any sort of testing if it will vary so much with the ambient temperature.

I would like to think this is not by design, and indeed it is a fault with this unit.

I have gone back and forth via email (starting on May 23rd), but it is painfully slow to get a reply from DiveNav.
Ex: I emailed last Friday (July 8th), and re-sent that same email yesterday (July 12), but have yet to receive a reply.

I posted here asking for a phone number to discuss, and they suggested email and their support forum.
I went to their forum, but I don't see a place to register, so I cannot post.
I registered on the main site, and can login there, but that login doesn't work on the forum.


Ideally I would like to get a replacement, unless this is normal in all units, in which case I would like to return it for a refund.
I'm going on a 2 week trip on the 21st, and I'd like to be able to use it then.


Thank you.

 

[DiveNav]

...... 1- I placed the CooTwo in a ziplock bag, along with a thermometer, and simply turned it on when indoors at A/C room temperature and took a pic of the reading..

Your experiment is not correct.
cootwo, as any other analyzer, must be used in presence of a constant gas flow (we recommend ~2 Lit/min. See our tutorial for more info)

..... I have gone back and forth via email (starting on May 23rd), but it is painfully slow to get a reply from DiveNav..

We have responded to most of your emails. We did not respond to the ones that did not make any sense.
We also requested you to return your cootwo so we could test it in our factory.

..... ....I went to their forum, but I don't see a place to register......

You can register here.
As of today we have more than 85,000 registered users.

..... Ideally I would like to get a replacement, .....

Your unit works fine as long as you use it properly.

 

[Got2Go]

Hello,

And thank you for your help.

I will try to address your replies below in hopes that you can help me understand what I might be doing wrong.

Your experiment is not correct.
cootwo, as any other analyzer, must be used in presence of a constant gas flow (we recommend ~2 Lit/min. See our tutorial for more info)

Ok. I repeated the experiment, but this time I used your flow metering device, connected to the analyzer, and to an AL80 cylinder with air, via low pressure inflator hose. I ran air through the analyzer for more than a minute in all tests. All tests done with the same cylinder/air/reg/LPI hose.

1- Indoor room temperature. CO reads 0.4 PPM, temperature is 74.8f.



2- Placed analyzer outside and let it acclimate to the new temperature.
Then connected to cylinder and analyzed the air.

CO reads 2.0 PPM , temperature is 106.7f.



3- Brought the analyzer back inside and let it acclimate to the lower temp.
Then connected to cylinder and analyzed the air.

CO reads 0.6 PPM, temperature is 78.3f.
Interestingly, the O2 reading also changed here to 21.4.
Same air. Same cylinder. Same reg/hose. All tests done within an hour after calibrating the O2 sensor wit this same cylinder. This cylinder has never been filled with anything other than air.



This still tells me that the measured CO values are highly dependent on ambient temperature (or temperature of the analyzer itself).

These temperatures are within your published operating range of 41f to 113f.

I watched a few tutorials, including My Nitroxbuddy app warnings, but could did not see information that might help me determine what I might be doing wrong.

We have responded to most of your emails. We did not respond to the ones that did not make any sense.
We also requested you to return your cootwo so we could test it in our factory.

I am sorry you did not understand the email, perhaps a reply asking for clarification would be a more effective solution. I would be happy to clarify any confusion.

My reluctance to send it back is that unless there is an understanding that there is something wrong with the unit, there is no point in sending it back.
(That is what I am trying to do here, and tried to do via email)

Otherwise, it's just an exercise to confirm that packages can be sent back and forth via USPS.

You can register here.
As of today we have more than 85,000 registered users.

That is what I had done. Register there. And I can login there.

But when I go to the actual forum, that login does not work, and I cannot post any new threads.

Your unit works fine as long as you use it properly.

Ok. I am completely open to the idea that I may be using it incorrectly.
Can you please describe what I need to change in my process above in order to get correct readings while using it properly?


Thank you for your continued help with this issue.

 

[Got2Go]

Hello,

My last email and this thread remain unanswered, so I figured I'd give it a bump in case @DiveNav missed it.

Thank you.

 

[DiveNav]

Please contact customer.service@divenav.com to request RMA so we can take a look at your unit.

 

[Got2Go]

Please contact customer.service@divenav.com to request RMA so we can take a look at your unit.

Thank you for your reply.

I have a second, new-out-of-the-box, Cootwo, and will be repeating the test again with both units at the same time.
Once I complete the test, I will post the results here.

Thank you.

 

[jzipfel]

Any update on this?

 

[tursiops]

Any update on this?

My guess is everything is now OK, since people tend to post problems and complaints but not when all is OK.

 

[Got2Go]

Any update on this?

Here is an update:

I sent a link to this thread to Mike Pedersen @ Dive Right in Scuba.
He offered to send me a 2nd new unit to test out.
(Is that awesome customer service, or what? unbelievable!)
(read above for a contrasting experience)

This was just before a trip out of the country, but I had a chance to do a quick test.
The quick test showed similar behavior on the new unit from DRIS.

When I came back a few weeks later, I repeat the tests but the results were inconclusive.
I could not reproduce the exact same issue, although both units still showed elevated CO levels when warm (but within specified operating temperature).

I did some additional testing, and found that the new unit from DRIS seems to always be about .3-.5 PPM CO higher than the original unit.
So it seems, at least on the CO, the readings are inconsistent between both units, and also vary depending on the temperature of the units (EX: warm from the sun/outside air).

As another test, I tested using 100% O2, and both analyzers showed 0ppm CO, as expected.
But then I quickly connected it back to an air cylinder, and ran it for a bit until it stabilized.

Original unit stayed at 0PPM CO, but the new unit climbed from 0 to 1.8PPM CO.




I don't have an answer, but this makes me scratch my head.

1 brand new analyzer, and a second fairly new one (that has already been back to DiveNav), and they don't agree on their CO measurements of the same gas.

I'll try to run some more tests before sending one of the units back and post any new information here.

Thanks for reading.

 

[laikabear]

I posted the following in another thread but wanted to put it here also for completeness and to get feedback from anyone watching this thread but not the other one:

"I have mine set to read CO in whole #s not tenths. It generally reads 0 or 1 ppm on a tank, occasionally a 2. Ambient air may go up to a 3, especially if I am cooking (gas stove). But, those are all "acceptable." People who get sick from high CO in a tank aren't sick from 1.8 ppm. I am expecting the unit to save me from getting sick (or worse) by telling me if there is 5+ ppm in a tank. I think it's just not accurate to the extra decimal place. Once you did the testing outside the bag and got only a variance of 0 to 2 ppm (my rounding), I think that's acceptable. Right? There was some discussion of setting it to whole #s rather than 10ths on another thread, but I forget which one.

I have never seen a CO reading over 3 ppm on mine. A more expensive analyzer might be both more accurate and more precise, but I don't know that is necessary for our application. Another thread listed people's personal cut-off for diving a tank. I think 5-10 and I'd be asking for another tank. Anyone else want to chime in with a different opinion?"

DRiS is great, aren't they? I have had some great customer service from them in response to a snafu in the past. They really go out of their way to take care of you. SO rare these days.