Analyzer Sensor Died

[rob.mwpropane]

I read through a few threads, but most pertain to RB's. Yesterday I was using my Analoxii O2 analyzer and the reading was @ 8.2... way off. Tried to calibrate it but it really didn't do anything. Tried removing the battery and plugging back in and resulted in the same reading. Battery was good so I replaced the sensor and all was well. It's odd, I didn't think they failed like that? What's really odd is I just used it within the last 2 weeks and readings were spot on after mixing some tanks. I thought they normally just start to drift from a known reading?

Since we're on the subject, anyone have any recommendations for how and how often to check? I have plenty of 100%, have to check my supply of 21% and see what I have left!

 

[SpeedyJ]

Sold industrial gas detection systems for years. O2 sensors are fickle beasts. From the same batch of sensors you can get one that lasts two years, one that started drifting within 6 months, and one that made it 6 days past the one year warranty mark and just stops working. In the industrial world most manufacturers would recommend a full calibration every 3-6 months using NIST gasses.

With my Divesoft analyzer, I tend to just use the single point calibration on air and let it run for a little while before analyzing to watch for drift. I've played with the two point calibration, but haven't seen the need to use it.

 

[Watthem]

You should be checking it against a known good source every time you use it, and it is possible for the sensor to have corroded in between uses enough (or otherwise degraded) quickly to the point where it is egregiously off

 

[rob.mwpropane]

Sold industrial gas detection systems for years. O2 sensors are fickle beasts. From the same batch of sensors you can get one that lasts two years, one that started drifting within 6 months, and one that made it 6 days past the one year warranty mark and just stops working. In the industrial world most manufacturers would recommend a full calibration every 3-6 months using NIST gasses.

With my Divesoft analyzer, I tend to just use the single point calibration on air and let it run for a little while before analyzing to watch for drift. I've played with the two point calibration, but haven't seen the need to use it.

I have read that they can be fickle. The only way that I know to calibrate is make sure it has either good ambient air around it or 100% out of the bottle and wait. I really don't like to waste the O2 so normally I just use air.

You should be checking it against a known good source every time you use it, and it is possible for the sensor to have corroded in between uses enough (or otherwise degraded) quickly to the point where it is egregiously off

Like air? How would it corrode? (understood about degrading).

It's just really wild to me that it worked right up until it didn't and then it was dead. I mean, I guess I would prefer it that way vs being very slow about it.

 

[Watthem]

Like air? How would it corrode? (understood about degrading).

It's just really wild to me that it worked right up until it didn't and then it was dead. I mean, I guess I would prefer it that way vs being very slow about it.

Any moisture getting into the has the potential to cause damage over time, even out of the air. The best bet for sensor longevity is to use a tank of normal air that will be extremely cool and dry when calibrating the sensor.

 

[rob.mwpropane]

Any moisture getting into the has the potential to cause damage over time, even out of the air. The best bet for sensor longevity is to use a tank of normal air that will be extremely cool and dry when calibrating the sensor.

I keep it in a dry box with the little sensor saver piece in it unless I'm using it. Usually I just turn it on and let it adjust in ambient air and then use it. Should I always calibrate with tank air?

 

[Watthem]

I keep it in a dry box with the little sensor saver piece in it unless I'm using it. Usually I just turn it on and let it adjust in ambient air and then use it. Should I always calibrate with tank air?

I'm sure you'll get varying answers on this and you'd probably be fine either way, but if it's feasible for you to have tank air on hand to calibrate with I'd recommend it as an extra precaution for the longevity of your sensor

 

[sprockjohnson]

I use the same o2 cells from my rebreather after they have been cycled out at the 12-18 month mark. For the analyzer, I always calibrate on dry air from a tank before analyzing the target tank. This might be OCD and unnecessary but I also check all my cells, those in the rebreather and the older cycled out cells, for linearity and current limiting using a pressure pot cell checker in pure o2 on a bi-annual basis. That seems to weed out any bad or dying cells.

 

[rob.mwpropane]

I use the same o2 cells from my rebreather after they have been cycled out at the 12-18 month mark. For the analyzer, I always calibrate on dry air from a tank before analyzing the target tank. This might be OCD and unnecessary but I also check all my cells, those in the rebreather and the older cycled out cells, for linearity and current limiting using a pressure pot cell checker in pure o2 on a bi-annual basis. That seems to weed out any bad or dying cells.

That seems like overkill for me though.. yeah? I mean the pressure pot thing?

 

[sprockjohnson]

That seems like overkill for me though.. yeah? I mean the pressure pot thing?

That depends on how high a ppo2 you expect to read with the cells. If you take the rebreather out of the equation then you won't be analyzing anything higher than 100% o2. I built the pressure pot cell checker specifically for checking my rebreather cells but have found that it helps to get an idea on cell health. I use my El Cheapo style analyzer for blending nitrox through my compressor so it's good to know that the cells are linear and not severely current limited when doing so.