New sensor - what should I expect

[scubanimal]

I opened my new 02 sensor to plug into my Drager Oxy gauge. I reads 25-26 O2 in an open room. Not attached to a lung or any tank.

Is this normal? Is there a burn in time or something? Or is this a defective gauge?

This seems to be a less than perfect item. Last week during training, both (new) sensors that were to be used with the class unit (uwtec) were defective reading from 26-135% when on the tank. We ended up not using any PPO2 gauge.

Thanks,

 

[caveseeker7]

Am not sure how the Oxygauge reads, I never used one.
But if the 25-26 are % O2, or .25-.26 ata pO2, then you're close.
You room should have 20.9% O2. Calibrate the gauge so it reads 20.9%.

If you have a tank with a known mix hook it up, do a loop flush and calibrate against that. At 1ata surface pressure that's the highest you could calibrate for with 100% O2. If possible, always calibrate with highest known O2 mix you will dive.

If you know the nominal mV output of your cells you can also check them with a voltmeter to see if they're in their operating range.

 

[Camerone]

I opened my new 02 sensor to plug into my Drager Oxy gauge. I reads 25-26 O2 in an open room. Not attached to a lung or any tank.

Is this normal? Is there a burn in time or something? Or is this a defective gauge?

Sounds right spot on. I agree with Caveseeker here; sounds like all you need to do is calibrate the OxyGauge. I don't have one (although I've played with 'em a few times.) I think it's either five or six pushes of the switch to set it to calibration mode, within the first few moments after you turn on the OxyGauge. Then you need to do the usual confirmation presses. The OxyGauge manual is clearer... I've never dived on the unit - I use a VR3 with mine, and, in the past, used an Oxy2. The procedures are similar, though, in that all of them need calibration. If I remember, the OxyGauge can only be calibrated with air as the calibration gas.

It actually sounds like almost all the sensors you tried were just fine. Each sensor's output will be slightly different, and varies a bit as to age of cell, time that it's been exposed to air, pressure (yes, changing weather patterns will affect surface readings), etc.

The very high reading (135%?) might be due to using the wrong cell type, if they weren't all the same. Generally, there are 10mV and 20mV (nominal, in air) cells. The Drager unit takes the lower of the two, IIRC. Don't know if you were using a batch of the same cell types or not. 10 mV cells should generally read anywhere from about 7 mV at the end of their lives to almost 13 mV at the beginning, when they're fresh, if you were to check the voltage with a multimeter (read the outside two pins of the three, if it's a molex connector type...) Verification with a multimeter is the only true way to check cell behavior. Verify that it's 7 - 13 mV in air, then, optionally, put it in pure O2 (at 1 ATA) and verify that it's _roughly_ five times as great in value as your air reading. Cell response is linear, more or less, with oxygen content.

Remember to do your calibration, for the Drager, in air, and not when connected up to the bag. The bags, if assembled, might be under pressure, and could contain residual gas from setting up the loop, if you've been checking flows, or may cause too low a reading (if you've sucked the loop down to a negative pressure test, then you'll actually find the Oxygauge reads a little low if you calibrated properly - about .19 on the surface...)

When using new cells, it takes several hours after opening the sealed package, or removing the cell from an inert environment, for the cell to begin reading correctly. Personally, I never trust a cell that's been exposed to air for less than 6 - 8 hours, from personal experience, regardless of what the manufacturer's literature says. Generally, if I can, I open cells the day before I install them into any equipment I'll actually dive. The one hour or so on the package is simply not enough time to let the readings stablize after the cell has been "sleeping." Sure, it'll read something, but not stably enough to trust.

 

[scubanimal]

Thank you guys. The sensor was fresh out of the package and I had just assumed that it would be at 20.8. I will find out how to calibrate and proceed.

The sensors in the Uwtec unit were new, I only know the symptoms I saw. After first calibrating it, when hooked up and in the loop with 50% 02 on it read 135%, after disassembly, re-init, re-calibrate and normal readings in air, hooked back up, with 50% 02 it read 85%. I just gave it back to the instructor and did the dive without it.

Thanks again.

 

[Dive Bear]

I dive a Drager with an Oxyguage. I've had it almost two years and so far it is a good dependable unit. If you are going to calibrate the Oxyguage, you must do it within a few seconds of power up. To calibrate the Oxyguage, remove it from the counterlung. Turn the Oxyguage on, then press the button six times. You should see a flashing "CAL" on the screen. Press two more times and let the unit calibrate itself. The unit should report CAL OK. That should be it.

Be aware that when you first unpack a sensor, it's going to read funny. Just let it sit in open air overnight, then calibrate the unit and you should be set.

I keep my sensor in an old 35mm film container in my refrigerator. When I want to go diving, I pull the sensor out about two days early and let it come up to room temp before I open the film can. Then I put the sensor back in the Oxyguage and let that sit overnight. This may be overkill, but it's the way I do things and I've never had a problem. I've been using the same sensor for about 18 months, so its about time to change it. In fact, I've been told that I'm a fool for not changing it already.

Let me add that I am NOT and instructor or a trained Drager tech. Please get a copy of the Oxyguage manual and read it cover to cover and NEVER dive the Drager without some kind of O2 guage. The Drager is just about as simple as a rebreather can be, but it will still kill you GRAVE YARD DEAD if you don't know what your doing.

If you need a pointer to the manual, I may still have it in my bookmarks, just PM me.

 

[Life-Is-Good-Diver]

I dive a Drager with an Oxyguage. I've had it almost two years and so far it is a good dependable unit. If you are going to calibrate the Oxyguage, you must do it within a few seconds of power up. To calibrate the Oxyguage, remove it from the counterlung. Turn the Oxyguage on, then press the button six times. You should see a flashing "CAL" on the screen. Press two more times and let the unit calibrate itself. The unit should report CAL OK. That should be it.

Be aware that when you first unpack a sensor, it's going to read funny. Just let it sit in open air overnight, then calibrate the unit and you should be set.

I keep my sensor in an old 35mm film container in my refrigerator. When I want to go diving, I pull the sensor out about two days early and let it come up to room temp before I open the film can. Then I put the sensor back in the Oxyguage and let that sit overnight. This may be overkill, but it's the way I do things and I've never had a problem. I've been using the same sensor for about 18 months, so its about time to change it. In fact, I've been told that I'm a fool for not changing it already.

Let me add that I am NOT and instructor or a trained Drager tech. Please get a copy of the Oxyguage manual and read it cover to cover and NEVER dive the Drager without some kind of O2 guage. The Drager is just about as simple as a rebreather can be, but it will still kill you GRAVE YARD DEAD if you don't know what your doing.

If you need a pointer to the manual, I may still have it in my bookmarks, just PM me.

Hey Dive Bear, when you say it can kill you, not having a PPo2 sensor or some type of device to track PPo2, im confused.

I thought the Drager Dolphin, they way they set up there equation's, and flow rate's, etc, a PPo2 Sensor , or oxy2 etc deivce is not needed?

Correct me if im wrong, but if you use the unit the way the manafactour recommend's, ( not switching flow rates to accomadate less gass consumpution , etc )
I tohught the way Drager set up the unit, PPO2 metering was not nessary?

reason why im asking, im diving the Dolphin and havn't decided on either the VR3 , or the Uwatec Air Zo2 and Oxy2, so if im diving the unit with what they reccomend, do i really need to stop diving it today till i purchase somthing? Im selling the HS Explorer PPO2 right now on ebay for reading PPo2, and been using that the last few times, but i thought it was ok to not have one, i just have to watch on the surface that i don't over work, im a newbie on rebreather's, only been certifed for a few month's, but thanks!

 

[caveseeker7]

... i just have to watch on the surface that i don't over work, im a newbie on rebreather's, only been certifed for a few month's, but thanks!

You have to watch what?

Actually, that's your answer.
Not just on the surface, in shallow water, too.
If in doubt exhale a breath through your nose or do a loop flush.
Never forget them before ascent, too.
Then you should be fine. Regurlary check a pO2 gauge and you will be fine.

 

[Dive Bear]

Hey Dive Bear, when you say it can kill you, not having a PPo2 sensor or some type of device to track PPo2, im confused.

I thought the Drager Dolphin, they way they set up there equation's, and flow rate's, etc, a PPo2 Sensor , or oxy2 etc deivce is not needed?

Correct me if im wrong, but if you use the unit the way the manafactour recommend's, ( not switching flow rates to accomadate less gass consumpution , etc )
I tohught the way Drager set up the unit, PPO2 metering was not nessary?

reason why im asking, im diving the Dolphin and havn't decided on either the VR3 , or the Uwatec Air Zo2 and Oxy2, so if im diving the unit with what they reccomend, do i really need to stop diving it today till i purchase somthing? Im selling the HS Explorer PPO2 right now on ebay for reading PPo2, and been using that the last few times, but i thought it was ok to not have one, i just have to watch on the surface that i don't over work, im a newbie on rebreather's, only been certifed for a few month's, but thanks!

I will never dive any rebreather without some kind of PO2 gugage. If I were on a dive boat, and my Drager Oxyguage punked out on me and I could not find a replacement, I would not dive the unit. It is true that if all goes well, and you use the proper gas mix you stand a very good change of getting away with it. BUT! All it takes is a tiny bit of trash in your sonic jet. You could have a sudden reduction in gas flow. Or it could stop gas flow altogether. If you have a gas injection problem, you can still breath on the unit until you pass out. This has already happened once that I know of. A Drager diver had a fatal accident in puget sound. I bumped into the person that examined the reberather for the police report. He told me that he found some kind of very small mineral deposits around the gas jet and flow was reduced to less than half of normal. This is why you should always check the system with a flow meter before each dive, and you should never dive a rebreather witout a PO2 guage. Hypoxia is a very sneaky killer, know your PO2 at all times.

Be safe

 

[Life-Is-Good-Diver]

Ok, makes sense, i used the HS explorer, single cell the last few times, but i may be computerless for another 2 weeks, till i can figure out what im going to do with PPo2, the VR3 is a nice computer, but only reads one cell, to bad they don't have a 3 cell unit for the VR3 so when i goto CCR, i wouldn't have to worry about PPo2.

Im looking at all my options right now for both SCR and CCR, just sold my computer, so now im computerless !!