Ran out of air today...

[openmindOW]

As a former IT consultant turned dive instructor, I have this inbuilt paranoia about anything computer-related... so it's all analogue backups for me!

I agree with you on this Crowley.

 

[Thalassamania]

Gauge errors are often non-linear. Zero errors such as you experienced are the most dangerous. We calibrate our SPGs with a fancy instrument known as a "dead weight tester" and make marks on the face every 500 PSI if there is an error.

 

[Jorgy]

Thanks for sharing and an important lesson for us all.........

Back in my Navy electrician days, when we were checking if a circuit was dead we had to do the following......

1 - Check the meter on a known live source
2 - Check the circuit was de-energized
3 - Recheck the meter on the same known live source

This was to make sure the meter had not failed during the critical circuit check......

When I gear up, I always.........

1 - Hook up my reg, pressurize the system
2 - Look at the gauge to make sure I have a good fill, check for leaks, free flows, etc....
3 - Close the valve and depressurize the system, by filling my wing with the air from the hoses

I always make sure the system is fully depressurized. This also prevents accidentally jumping into the water with your gauge showing 3000 psi but the tank valve shut unfortunately I see this and no air in BC quite frequently.

M

 

[fppf]

Gauge errors are often non-linear. Zero errors such as you experienced are the most dangerous. We calibrate our SPGs with a fancy instrument known as a "dead weight tester" and make marks on the face every 500 PSI if there is an error.

And where do you have access to a dead weight tester? And why would you test a 5% or even 1% gauge with a dead weight, that's like trying to cut butter with a laser cutter.

I also hope your dead weigh tester is a high pressure gas version. If its not, I hope its at least water based for its media and that you bake your gauge to remove any water from the Bordon tube when your done. Most dead weights in that pressure range use oils.

I just use a dead weight to calibrate my 0.1% pressure transducers. Then I use those to test everything else. That gives me a 10:1 TUR for a 1% gauge and still a 5:1 for a 0.5% gauge. My transducers are strain gauge diaphragm types, so O2 cleaning after cal is easy.

 

[Thalassamania]

In the Marine Tech group At the Oceanographic Institution I used to work at,

We were interested in seeing exactly what the errors were and following them over time, and the gear was sitting there.

What we found was that there were individual SPGs that were good to go and pretty much stayed that way, there were others that were not very good stayed that way, but zero error was very rare in new gauges and did not appear within the seven years that we did the testing. Error elsewhere in the scale was common and gauges changed from one year to the next.

This was how we developed the standards that were used in "SCIENTIFIC DIVING: A GENERAL CODE OF PRACTICE" N.C. Flemming and M.D. Max (eds)

 

[dumpsterDiver]

Those guages can be damaged by shock also. Maybe you would be safer if you put a nice big soft rubber boot or console around that naked gage...

 

[Dive Right In Scuba]

And I thought only computers failed

Glad your OK!!!!

 

[mrfixitchapman]

I was the air donor on a dive charter in the Florida Keys. Buddy was my daughter on her third open-water dive. I was happy to help, and glad that I was there. She was pretty rattled. The gauge showed almost 800 psi. On an empty tank. I showed this malfunctioning rental gauge to the boat driver. Without saying a word he picked two 4-lb. weights out of the crate. Set one of the weights on the deck, placed the offending gauge on top of it and used the other weight as a hammer to crush the gauge to death. My daughter used his personal rig for the next dive. That boat driver sold his dive op to some guy named 'Gary .... something'

DC

 

[diverrick]

No one seems to be the least concerned that he came up with les than 500PSI to start with.!!
Where I come from, that last 500 PSI is for last ditch emergencies, not for another ten mins under water. Maybe I am just conservative, but then again, I am still alive, after 30 plus years diving. Most dive ops require you come up with at least 500 psi The only exeption if your diving so shallow you could come up no problem in one breath. Not a common occurance

 

[Dive Right In Scuba]

No one seems to be the least concerned that he came up with les than 500PSI to start with.!!
Where I come from, that last 500 PSI is for last ditch emergencies, not for another ten mins under water. Maybe I am just conservative, but then again, I am still alive, after 30 plus years diving. Most dive ops require you come up with at least 500 psi The only exeption if your diving so shallow you could come up no problem in one breath. Not a common occurance

Because his gauge was broken.....had it not been broken, he would have been around 500PSI, and this was after his safety stop, so he was safety driven