Comfort Zone - What range of Gas Analysis?

[Akimbo]

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Unfortunately, it seems a lot of people believe whatever said computer / measure device says. I thought I would hear more people give a 'brain check'.

That was precisely my point: you needed to give a brain check...

It is interesting. There is a false expectation of accuracy and resolution when the display is digital compared to analog meters. Micro fuel cell precision has not changed but lots of people expect +/- 0.1% overall because that’s what the display implies.

Analog displays inside hyperbaric chambers still have some advantages over digital. They don’t require batteries or electronics. The fuel cell can drive the analog meter directly through a potentiometer for calibration. Digital displays can also have problems when compressed/decompressed too quickly.

 

[The Chairman]

It is interesting.

The interesting part was the immediate distrust of the analyzer after propor protocol had not been followed. It's a tool. You have to use it correctly in order to get the desired results. A hammer makes a lousy screwdriver and a screwdriver makes a lousy hammer. Both can and have been used and for various reasons. When you only own a hammer, the world is filled with nails.

Many, many years ago, I ran the student machine and welding shop for the College of Architecture at UF (Go Gators). I would set them up, make sure they were comfortable and then listen. I could always hear when they were abusing it. The best was the band saw, and when it started to howl and the kids stated swearing, I often reminded them "It's not the tool!" Protocol for any gas analyzer is to simply calibrate it against a known gas and ascertain that it remains stable after it's been on a few minutes. The more ideal and consistent the conditions, obviously the better the measurement. If you get a funky reading, before you question the device, go back over the protocol. Did you omit steps or simply didn't bother? Get the protocol down before you question the tool.

Here's another anecdote, when I went to work at a Nissan Dealership, a guy named Henry was doing the the warranty work for them. Henry's a nice enough guy, but he's highly excitable and prone to making the wrong conclusions. Anyway, I was given a number of 'problem' vehicles, not only so they could get a feeling for my mechanical aptitude, but also to get a fresh set of eyes on the problem. One was a Z car who's ride control was not working. It was always a harsh drive, and it was being returned under Florida's Lemon Laws. Henry had spent days on the car. In his words, he had been over it with a fine tooth comb and it HAD to be the RCM (Ride Control Module) or the brain.Yes, Henry thought the Z car needed a brain and he was quick to condemn all electronics because of this. A quick test drive and it was obvious that the smallest bump could cause you to crack a tooth. I put it in the air and inspected the suspension. Lo and behold, the shipping blocks were still on all four struts. Instead of four springs supporting the vehicle and the sway arrested by the struts, the weight of the vehicle was transmitted straight through these hard rubber spacers. They're supposed to come off during vehicle prep at the dealership, but someone messed up. Well, so had Henry. With a flourish for the melodramatic, my boss but a string through the blocks and hung them in our rest area with the sign: 'Henry's Brain!' Henry didn't like me much after that, but the take away here is that humans make far more mistakes than the electronics we rely on. Far more.

 

[Akimbo]

The interesting part was the immediate distrust of the analyzer after propor protocol had not been followed….

Especially in the case of gas analyzers, distrust is much safer than blind acceptance. Perhaps not distrust but skepticism. This is especially good when proper protocol has is not being followed due to misunderstanding, misinformation, or even ignorance.

Yes, analyzers are tools, but more specifically they are instruments. None of my dozens of hammers have ever lost calibration. I’m don’t think we are actually debating here as opposed to placing human tendencies in context.

… A hammer makes a lousy screwdriver and a screwdriver makes a lousy hammer….

OK, now you have lost me. Are you saying that there are some tools that aren’t actually hammers???

Everything is a hammer, in the hands of a commercial diver. There’s a Crescent Hammer, Shackle Hammer, Caveman Hammer (rock), and BFK Hammer just to name a few. I once considered using my Bailout Bottle Hammer but thought better of it.

 

[The Chairman]

Especially in the case of gas analyzers, distrust is much safer than blind acceptance. Perhaps not distrust but skepticism. This is especially good when proper protocol has is not being followed due to misunderstanding, misinformation, or even ignorance.

Yes, analyzers are tools, but more specifically they are instruments. None of my dozens of hammers have ever lost calibration. I’m don’t think we are actually debating here as opposed to placing human tendencies in context.

The skepticism should be placed on the user first. If they are using it right and following the protocols, then you suspect the analyzer. For most people, the analyzer is simply a black box they just don't understand much like the on board controllers most cars use. To them, it's always the computer's fault and in reality it's very seldom the case. Murphy's Law (which was initially Murray's law, but there was a typo at the printers) tells us that it works better if you turn it on and more so if you plug it in. It's why most PC problems fall in the PEBCAK folder.

Customer complains of rattling sound:

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For those who don't know, the hanger is replacing an exhaust hanger. Kinda ironic and sad at the same time.

OK, now you have lost me. Are you saying that there are some tools that aren’t actually hammers???

You mean, like an O₂ analyzer? Or a PDC? Or an SPG? Or your mask? Or... I could keep this up for a while.

 

[Akimbo]

…You mean, like an O₂ analyzer? Or a PDC? Or an SPG? Or your mask? ...

Yeah, like those. Of course you want to go easy on the glass parts.

 

[waterpirate]

I am late to the discussion, but here is my take. I am a math idiot. When I put together my fill station, like everyone else before me I was scared to death about results. I PP trimix and mix nitrox on the go. It only took me about 2 weeks to figure out that a fill operator with two different annylisers is as confused as a diver running two different putters.

I trust my input math on blending and verify the result with my annyliser. Because I regulate the 02 to the compressor manualy by sight, as the pressure rises it warrants a reduction in the 02 input, based on volume. This yields a plus or minus 2% 0n the 02. The dominant gas. I trust my annyliser. Change my cell yearly or more frequently as indicated.

I will answer that when my reading vary more than 2% one way or the other, I check my process and my annyliser.
Eric

 

[Jax]

That was precisely my point: you needed to give a brain check.

The interesting part was the immediate distrust of the analyzer after propor protocol had not been followed.

You jumped to HUGE mis-conclusion. :shocked2:

The fact of "brain check" = needing a calibration led to "I wonder what variance is in the comfort zone of most people."

It's just that simple.

The answer seems to be, most people don't think about it.

---------- Post added February 7th, 2015 at 05:35 AM ----------

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I am a math idiot. . . .

I will answer that when my reading vary more than 2% one way or the other, I check my process and my annyliser.
Eric

It seems that those of us with hard science backgrounds have considered this.