Equipment Pressure gauge

[dmaziuk]

Probably threw away a perfectly good SPG

The metal in the bourdon tube does get fatigued and it becomes progressively less accurate with time. If it's as old as it sounds, maybe it was time to retire it -- even if you could pull it apart and service the moving parts.

Looking at my DGX one, I don't think I'd care to try: disassembly looks doable with a big enough hammer, but I have doubts about putting it back together afterwards.

 

[Still Kicking]

A guage that reads a little low is NBD. A gauge that reads a little high goes to the scrap bin.

 

[Zef]

A guage that reads a little low is NBD. A gauge that reads a little high goes to the scrap bin.

Realistically, an SPG is inexpensive and easy enough to replace regardless of issue, but a reading of a little high or a little low is not an issue if the reading is consistent....the issue is when there is a change, then the gauge cannot be trusted.

-Z

 

[Pavao]

I think the real issue is running gas reserves so low that a small discrepancy in the SPG reading becomes an issue.

 

[Zef]

I think the real issue is running gas reserves so low that a small discrepancy in the SPG reading becomes an issue.

It is an interesting thing and I agree with what you said above, but I would add that it is important to have a good idea where the needle is tracking on the guage dial every time one looks at it so that they don't find themself breathing the tank dry with a stuck needle giving the false impression that they have any air left.

When I dive with my air integrated computer and transmitter, I have a constant readout of my tank pressure and remaining air time based on my current breathing rate. The computer is on my right wrist/forearm and I dive in a manner that it is nearly in constant view.

When I dive with a non-AI computer and SPG, I often look at my gauge and register where the needle is relative to the markings on the gauge and mentally note that I have enough air left or need to move up in the water column, or turn the dive, etc. But the only time that I really note how many bar or PSI I have is when my buddy asks for my air pressure, or if I am responding with mine after asking my buddy for theirs. But if more than 30 seconds goes by and one was to request my air pressure again, I would have to look at the gauge as I don't, for some odd reason, retain the info.

Its kinda like no matter how many times one writes the date, one has a tendancy to look at their watch to remind themself what the date is...even if they just wrote down the date 5 minutes prior.

I believe the phenomenon is called "cognitive slip", and it would probably be safer if I made more of an effort to note and maintain cognizance of the actual pressure reading when I look at my SPG...

...but I know from my diving experience that I am not the only one who suffers from "cognitive slip" when under water. It is actually rather common.

-Z

 

[BRT]

It is an interesting thing and I agree with what you said above, but I would add that it is important to have a good idea where the needle is tracking on the guage dial every time one looks at it so that they don't find themself breathing the tank dry with a stuck needle giving the false impression that they have any air left.

When I dive with my air integrated computer and transmitter, I have a constant readout of my tank pressure and remaining air time based on my current breathing rate. The computer is on my right wrist/forearm and I dive in a manner that it is nearly in constant view.

When I dive with a non-AI computer and SPG, I often look at my gauge and register where the needle is relative to the markings on the gauge and mentally note that I have enough air left or need to move up in the water column, or turn the dive, etc. But the only time that I really note how many bar or PSI I have is when my buddy asks for my air pressure, or if I am responding with mine after asking my buddy for theirs. But if more than 30 seconds goes by and one was to request my air pressure again, I would have to look at the gauge as I don't, for some odd reason, retain the info.

Its kinda like no matter how many times one writes the date, one has a tendancy to look at their watch to remind themself what the date is...even if they just wrote down the date 5 minutes prior.

I believe the phenomenon is called "cognitive slip", and it would probably be safer if I made more of an effort to note and maintain cognizance of the actual pressure reading when I look at my SPG...

...but I know from my diving experience that I am not the only one who suffers from "cognitive slip" when under water. It is actually rather common.

-Z

I make a practice of thinking of how much pressure I have before I check the gauge. I am seldom off more than 100 psi.