Depth gauge at altitude

[airizzy]

I am a new diver and I live and will be diving at altitude. I purchased a navigational console(CG3206) because the dive shop owner said they only sell gauges that are altitude compensating. She explained to me that non-compensating gauges will flood at altitude and had no answer about errors due to altitude. The more I study altitude diving the less her explanation makes sense. My question is: Are your analog depth gauges actually compensated for altitude?(by this I mean the gauge is accurate at all altitudes.) If it is not compensated and is calibrated for sea level only will I need to apply a conversion factor to determine actual depth? Also I would like to know what drives your depth gauges. Are they bourbon tubes, capillary tube, or something else?

I am a mechanical engineer and an airline transport pilot and understand a little about pressure so please feel free to be as technical as you wish. I currently use altitude charts to determine the theoretical depth but like to understand the ins and outs of how they work. I know what you are thinking. I am probably over thinking this and should just buy a good dive computer and not worry about it.

 

[H2O 70]

I haven't heard that an analog gauge will flood, but they won't give you an accurate depth rating. They are calibrated for 1bar, sea level.

 

[mrfixitchapman]

Find the tables for altitude diving. Read and understand how altitude affects your dive planning. Then plan your dive and dive your plan. This is no place to 'wing it'.

DC

 

[airizzy]

I agree that this is "no place to wing it". Every time I talk to the dive shop owner, which was also my instructor, about depth gauges at altitude I never get a straight answer. She said the Sherwood gauge I bought compensates for altitude but every reference I have read about analog gauges at altitude talks about a conversion factor that must be applied to indicated depth to get actual depth. The math is not hard but you need the actual depth to get a good theoretical depth.

 

[inventor]

If in doubt, ask about.

Which you are doing here. If someone's answer doesnt jibe, find an answer that does. But keep asking. As an ATP, you do have some technical knowledge. Ask her to math it for you. Or, ask her to explain it in a different way. If she can't explain it differently, she doesn't understand it.

By the way, just a newb, 31 dives, single 'Introduction to Flight' lesson.

 

[Tortuga68]

I purchased a navigational console(CG3206) because the dive shop owner said they only sell gauges that are altitude compensating. She explained to me that non-compensating gauges will flood at altitude and had no answer about errors due to altitude. The more I study altitude diving the less her explanation makes sense

That's because it's crap

My question is: Are your analog depth gauges actually compensated for altitude?(by this I mean the gauge is accurate at all altitudes.) If it is not compensated and is calibrated for sea level only will I need to apply a conversion factor to determine actual depth? Also I would like to know what drives your depth gauges. Are they bourbon tubes, capillary tube, or something else?

No. Yes. Bourdon

You also need to compensate if diving fresh water

 

[mictrik]

I have a altitude compensating analog depth gauge. The gauge can be manually adjusted via a very small screwdriver (jewelers style) compensate for altitude. Simply zero out the depth reading and lock the zero...

 

[Thalassamania]

Run, do not walk, to another instructor, that woman is more than just a fool, she is a dangerous fool. Call her agency up while you're at it, she needs serious help.

 

[FritzCat66]

Are they bourbon tubes, capillary tube, or something else?

You definitely want the bourbon tube. Draw heavily from it and you can simulate being at any altitude you want. :biggrin:

Seriously, a bourdon tube gauge should be rather auto-compensating, but lots of computers including the Sherwood will adjust for altitude as well. Download the manuals from the manufacturer's website to check specs first!