SPG Calibration Off?

I had a strange experience while diving this weekend and was hoping someone smarter than me on this board could answer this for me. Here's the deal:
Made two dives with my usual buddy this weekend. Normally, we tend to have about the same air consumption and things were going as usual again. As I hit 1000 psi on the first dive, I signaled for us to go up, as is our usual procedure. He was at 1100 or so psi. As we ascend from 40', we make a 3 minute safety stop at 15'. I get out of the water with just over 500 psi, and he is at 1000.
Same thing happens on the second dive. We stayed shallow, no deeper than 20', down for maybe 30 minutes. At 900 psi we start ascending, again with a safety stop at 15', 3 minutes (Rob's at 1200 psi when we start the safety stop). Again, I surface with 500 psi, while he's at over 1000.
I didn't do anything strenuous or different than usual during these dives, but feel like there has to be something wrong. Either I'm turning into a Hoover, or my gauges are messed up. As I am typing this, I realize we should have hooked my tank up to his gauge after the dive, to see if it read differently.
Anyway, suggestions would be welcome.
T

ScubaThor:

As I am typing this, I realize we should have hooked my tank up to his gauge after the dive, to see if it read differently.
Anyway, suggestions would be welcome.
T

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Though I don't claim to be as smart, let alone smarter than you, I think you have already found a solution to your problem...

Z...

Definitely check your guage against his and a couple of others. Sounds like someones guage is off a bit.

You need to swap gauges and see what they say.

You will never use exactly the same amount of air on what appear to be identical dives, which they won’t be.

Many, many things, way to many to discuss here, govern the amount of air used. Comfort, attitude, amount of coffee, general well being and the list goes on and on will affect air consumption. What you did once, twice or three times is not necessarily what you will do in the future. It can be a guideline of approximates but not exacts.

I don't have a clue as to what your comfort level is underwater. But I would bet that when you saw that the two of you were off by 100psi, which is no big deal, you got concerned. That extra stress could have caused you to use a little more air.

Swap around two or three gauges and see what they read.

Gary D.

Gary D.:

But I would bet that when you saw that the two of you were off by 100psi, which is no big deal, you got concerned. That extra stress could have caused you to use a little more air.



Gary D.

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Thanks for the advice. I actually wasn't concerned at all and even made a point on the second dive to breathe even slower than usual so as to not waste air. We spent the last 5 minutes of the dive just sitting on a platform at 15', playing w/ fish, so over-exertion doesn't seem to be the culprit either.
I wish I had thought of switching gauges right after the dive....

Sounds like Haigh...LOL

jepuskar:

Sounds like Haigh...LOL

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How could you have possibly known? Did you make it down there this weekend? Water is getting colder already.

I can just see it now, "I can't be out of air, I am using his gauge!" :11: