cootwo oxygen sensor lasts for less than 1 year

[vovanx]

I've bought cootwo last June and recently found out that it gives incorrect readings: e.g. 88% for 100% oxygen and 25% for 28% nitrox (the higher the O2 content the bigger the difference).
so the oxygen sensor lasted for just half a year, which means that either my particular cootwo was lying in the warehouse for more than 6 months (thus giving the full one year of sensor life) or the oxygen sensor is faulty.

the point of my topic is: you should verify your gas mix with two different analyzers if you plan to stay close to MOD for prolonged period of time.

P.S. CO sensor is still working correctly - verified with different analyzer.

 

[rhwestfall]

When did you last calibrate it?

 

[tbone1004]

what @rhwestfall said. If you are testing at 100%, then you need to be doing 2-point calibration. It shouldn't be that far off. If it is, just get a new sensor. While DiveNav is not exactly known for their customer service, O2 sensors are not consistent so while it should last quite a while *my O2 sensor is going on 3 years*, I've also had them last 3-4 months.

If there's any chance you got the sensor wet *i.e. didn't blow the valve out all the way, was in the rain, wet gear bin, etc*, then the sensor would have been shot from exposure to water

 

[vovanx]

When did you last calibrate it?

a dozen of seconds before I analyzed nitrox tanks, on a nearby air tank.
or you mean the oxygen calibration? AFAIK cootwo does not allow oxygen calibration, only air.

 

[tbone1004]

@vovanx cootwo allows dual point calibration. I would recommend using it if the sensor is acting like that

 

[vovanx]

I've also had them last 3-4 months.

wow

 

[rhwestfall]

As @tbone1004 said, and IIRC, for very high O2 levels verification, 2-point calibration is stated in the manual.

 

[vovanx]

@vovanx cootwo allows dual point calibration. I would recommend using it if the sensor is acting like that

oh, it really does, but only thru the smartphone app.
I will try 2 point calibration and will report here later.

As @tbone1004 said, and IIRC, for very high O2 levels verifivation, 2-point calibration is stated in the manual.

yes, I found that already. I never use the app because I never use smartphone when diving, but will try next time I dive nitrox.

 

[vovanx]

wait. if an oxygen calibration lasts for several hours only, does it mean that I will have to calibrate the cootwo on some "reference oxygen" tank before analyzing the "actual breathing oxygen" tank, every time I need a high O2 % gas mix?
that makes no sense to me.

 

[tbone1004]

@vovanx O2 calibration will last as long as any other calibration, but yes you need to calibrate it against a known oxygen tank