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Thread: Calibration of Cells - Single point - 2 point -Air or O2?

  1. #1
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    Calibration of Cells - Single point - 2 point -Air or O2?

    Quote Originally Posted by Brad_Horn  View Original Post
    What I think is irrelevant, but its been proven that the oxygen cell calibration needs to be done in air as an EN61508 requirement for functional safety.....

    ....
    incredible naive bullshit

    so the WHOLE WORLD has it wrong? the US NAVY, all european military, all governmental institutions, all training agencies, all (real) rebreather manufactures, they are all wrong?

    what an incredible arrogance
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  2. #2
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    Re: Requests to Correct - incorrect data on the AD incident list

    Quote Originally Posted by Brad_Horn  View Original Post
    Ever found more than about 1% difference in the oxygen % in atmospehric air......
    incredible, so you even have never done a nitrox course?

    what's the O2% in air at 35C and 100% humidity?
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  3. #3
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    Re: Requests to Correct - incorrect data on the AD incident list

    Quote Originally Posted by Brad_Horn  View Original Post
    Paul, if they want a product that meets the EN61508 functional safety standard then that has been proven to be a requirement........
    real world physics don't just change because you post imaginary physics hundreds of times on forums, discussions, websites..

    maybe you start to believe it yourself after some time, but that does not mean that the world has changed
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  4. #4
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    Re: Requests to Correct - incorrect data on the AD incident list

    Quote Originally Posted by Brad_Horn  View Original Post
    What I think is irrelevant, but its been proven that the oxygen cell calibration needs to be done in air as an EN61508 requirement for functional safety.....
    While that may be your opinion, your opinion and fact still remain two different concepts.

    Calibration in air is certainly possible and is more practical for semi-closed rebreathers, but we have identified the following limitations of calibration in air:

    1. The calibration at 21% is significantly different from the typical operating range at around 140%. By calibrating at 21% and operating at 100% or more, the sensor is assumed to be very linear and not current limited. An advantage of calibration at 98% is that this is much closer to the typical operating range and less reliance is placed on strict linearity.

    2. Calibration at 21% involves approximately a 10mV signal vs. a 47mV signal, which is much more susceptible to analog noise and offset voltages in the amplifier circuits. A given level of noise or offset has almost a 5x greater impact when calibrating in air.

    3. The analog to digital conversion has a limited resolution, and quantization errors are almost 5x as significant with a 21% calibration vs. a 98% calibration.

    4. An argument could be made that a O2 calibration source may not have a precisely known O2 concentration, however, a 2% error in O2 level at around 98% nominal translates to only a 0.4% error in concentration at 21%. In other words, sensitivity to absolute errors in O2 concentration is less for a (nearly) pure O2 source as compared to air.

    If high purity cryogenic oxygen is not available for diving, it is still necessary to calibrate your oxygen analyzer with pure oxygen. You can then use your oxygen analyzer to set your dive computer to the correct value for calibration.

    Bruce
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  5. #5
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    Re: Requests to Correct - incorrect data on the AD incident list

    Quote Originally Posted by MeRodent  View Original Post
    Thanks Bruce, I was tempted to try explain with a similar level of detail but realised it would be a pointless exercise for Brad.

    I keep forgetting that there are others on the forum that will actually get something from informative posts so once again thanks.
    let's just add to the correct calibration discussion that humidity in air in warmer places can even add a bigger error than the ones already mentioned.

    correct calibration using oxygen is just a no brainer. and thus definately not a 'design issue of a unit' !
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  6. #6
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    Re: Requests to Correct - incorrect data on the AD incident list

    Quote Originally Posted by Brad_Horn  View Original Post
    Ben, assuming that both sets of 100 were both using an identical electronics setup (possible, though highly improbable), the difference lies in the OSEL recommendation to calibrate in air (easy to unscrew the pod to do this) and then check the loop result after an oxygen flush. So the Apoc divers would have calibrated correctly but then had a result equating to an incorrectly flushed loop, whereas the rEvo divers would have inc..........
    so.. good to know

    the APOC is calibrated when you open the unit and the electronics see light

    so Brad, you have not yet answered the question: what is the PPO2 of air at 35C and 100% humidity?

    it's easy to write that you have 'facts' when you copy a link of someones post on the internet.

    I prefer facts coming from pure physics, or from reports from independent reviewers

    the fact is: if you calibrate your unit on air the way you describe, your calibration is 10% off when you do this in 100% humidity at 35C
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  7. #7
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    Re: Requests to Correct - incorrect data on the AD incident list

    Quote Originally Posted by Brad_Horn  View Original Post
    If the system failed, it’s a design fault!
    OSEL have spent the money on the Apoc and the iCCR. It has a properly tested, fully certified and fully redundant system whose driver was functional safety. Lets see how that goes.......Brad
    ok, now that we are there, can you explain how the above is possible, when it is now proven that it cannot meet EN14143 when you calibrate with ambient air at 35C and 100% humidity?

    remember, EN14143 allows a maximum error of 0.06 bar when measuring PPO2 up to 2.0 bar

    calibrating in ambient air at 35C and 100% humidity will show a theoretical maximum of 1.886 bar PPO2 when exposed to a PPO2 of 2.0 bar
    (but usually it will show less because of non-linearity), so ..?
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  8. #8
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    Re: Calibration of Cells - Single point - 2 point -Air or O2?

    Quote Originally Posted by Brad_Horn  View Original Post
    Paul, An interesting question and not one I have an answer to off the top of my head. It certainly passes at up to 27'C and 50% humidity, which is the maximum required for EN14143!!
    I don't think so, these are the lab testing requirements

    these are in no way the limit of use of the unit, unless you specify that the apoc can only be calibrated at room temperture and MAX 50% humidity?

    the scope of EN14143 is in water till 34C: now please give me a location in the world where the ambient air is <= 27 and <50% relative humidity, while the water is at 34C ..

    so the unit does not pass functional safety, nor EN14143 in areas > 27C or > 50% RH ?

    btw: the lab testing requirment in EN14143 is MINIMUM 50% humidity, and not less then..
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  9. #9
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    Re: Calibration of Cells - Single point - 2 point -Air or O2?



    Rant time. Again. For some reason this chicanery /really/ gets under my skin because it's utterly negative and of no use or help to anyone.

    Paul: why do you bother? No-one else pays half a mind to this peanut gallery, apart from the visceral need felt by any sane person to choke the living shit out of this kind of smarmy used car pdf salesman and make the world a better place (which I wholeheartedly endorse, BTW).

    The peanut gallery isn't doing anything constructive, just trying to score "points" in some imaginary game. The outcomes of this game? Everyone gets angry, everyone gets a little more stupid just by osmosis, and diving a rebreather becomes a little less fun.

    Best thing I can think of when some clown act starts this kind of game?

    Don't play

    The general reading public with more than two brain cells to bang together can see straight through the bullshit. We might not be able to talk in circles like they can. So when we respond, trying to be civil, we get run around in circles and end up sitting there thinking "what just happened? How did this clown end up on top of this argument?". But, arguments aside, we know what's important:
    - You make a bloody incredible bit of kit. So does APD.
    - And, unlike the offerings from some other "manufacturers", they are real kit made by real companies staffed by real people with real history in the real world.

    I can go and buy one of either tomorrow, and dive it after a little training which I can get just about anywhere in the world. My mate can go and buy one too. We don't have to timeshare photos of some unicorn that someone claims to have dived but can't talk about unless we place an order for 10,000,000 units.

    - People have had issues with them. Both the rEvos and the AP units.
    - People have also had issues with cars. Televisions. Blenders. Stuff breaks, we know that. There's always room for design improvement. We know that too. So there's training to cover issues during the dive and service arrangements to sort things out once out of the water. Fantastic.

    Some pissant little company that's gone broke and changed names more times than a shark diver has changed his undies?
    1. On a scale of one being next to nothing vs ten being "this is the will of God", their collective opinion's value sits at about "fuck all".
    2. We know this.
    3. You know this (despite a perceived need to save face in the light of their antics).
    4. The only people who don't know this, really, are them. And in that case - see point 1.
    5. Don't play

    Those that can, do. Those that can't? They sit on the sidelines like vultures and peck and tear and rip at the good things and ruin it all for everyone. A pox on them all, I say.

  10. #10
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    Re: Calibration of Cells - Single point - 2 point -Air or O2?

    This could be a case of all publicity whether its good or bad publicity is great publicity.

    I never heard of this persons and their list til I seen the posts and angst from Paul and Co.

    Don't blame Paul for being upset especially when the persons in question are claiming to validate their credibility on opinions and spiteful explanations of rebreather Co's. products.

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