A Better SPG?

[SangP]

If you are deep enough to implode a brass and glass spg you are well beyond my capability on my best day, good luck.

N

The thing about pressure failures is that a small weakness on certain parts like the glass (from being dropped for example), a badly fitted/damaged o-ring is sufficient to cause pretty much anything to crack n flood. You don't need huge pressures to cause pressure failures.

One thing to note is that with anything filled with fluid/gel/oil, it can get really messy if there is a leak on land :shocked2:!

SangP

 

[Belce]

How about intergrating your computer with your spg? There are currently methods to do this with a hose or a wireless connect and they already do this.

 

[nielsent]

One thing i would like to see in an SPG (and I admit this is a bit off topic from where you are going, but I think would be great for a ease of use thing) would be having both a PSI and BAR scale put on the reading face, allowing for equipment to automatically convertable for those that work in both systems, and for those that only work in one that travel where their system is not used.

 

[Thalassamania]

What is the best pressure checking device typically available in which to check bourdon tube SPG's accuracy? In the absence of any future improvement in technology I am in favor of picking through an LDS's inventory for the most accurate gauge. I am a very simple fellow...

It is called a, "dead weight tester." As I noted in earlier posts:

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.
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and:

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)
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[Akimbo]

One thing i would like to see in an SPG (and I admit this is a bit off topic from where you are going, but I think would be great for a ease of use thing) would be having both a PSI and BAR scale put on the reading face, allowing for equipment to automatically convertable for those that work in both systems, and for those that only work in one that travel where their system is not used.

OMS makes some:

OMS Submersible Pressure Gauges (SPG's) http://www.omsdive.com

OMS Brass PSI/BAR Pressure Gauge,(52mm)

Dual scale can get a little busy but I personally like them. I don't think your comment is off topic at all. This is a good place to voice any thoughts on what you think makes SPGs better.

 

[Akimbo]

The thing about pressure failures is that a small weakness on certain parts like the glass (from being dropped for example), a badly fitted/damaged o-ring is sufficient to cause pretty much anything to crack n flood. You don't need huge pressures to cause pressure failures.

One thing to note is that with anything filled with fluid/gel/oil, it can get really messy if there is a leak on land :shocked2:!

SangP

Good point. I personally can’t recall any fluid filled depth gauges leaking. I have seen one occasion where several fluid filled industrial gauges were smashed, but that was the smallest part of that mess.

Does anyone have experience with oil leakage from mechanical depth gauges in the last 30 years or so?

 

[Nemrod]

Good point. I have personally can’t recall any fluid filled depth gauges leaking. I have seen one occasion where several fluid filled industrial gauges were smashed, but that was the smallest part of that mess.

Does anyone have experience with oil leakage from mechanical depth gauges in the last 30 years or so?

Yes, they do leak, I have had several. Then there is the annoying bubble that develops as a result and seems to always be right where I want to look.

N

 

[captain]

Other then damping the effect of shock to the gauge mechanism such as being dropped or pressure pulsations and vibration I see no real advantage to a liquid filled SPG as far as implosion is concerned.

 

[Nemrod]

I think they want to put a diaphragm or flexible backside on the gauge and use the oil filling to transfer ambient pressure to the gauge mechanism to correct the "usable" remaining air supply.

N

 

[Akimbo]

Other then damping the effect of shock to the gauge mechanism such as being dropped or pressure pulsations and vibration I see no real advantage to a liquid filled SPG as far as implosion is concerned.

The objective began with making an SPG for greater depths:

http://www.scubaboard.com/forums/computers-gauges-watches-analyzers/340231-operating-depth-spg.html

Fluid filling is one way to accomplish that and eliminates implosion risk. That automatically makes the SPG read relative to ambient or over bottom pressure. Another thread touched on calculating usable gas at depth. Those threads lead me to this discussion.