The accuracy of the SPG

[scubafanatic]

...well cornfed......that level of accuracy is kinda cool for SAC experiments/measurements.......plus I just like it, there's no reason not to have the most accurate spg......just a personal preference......and, apparently I'm not the only one that appreciates it...otherwise these products wouldn't exist.


Karl

 

[cornfed]

scubafanatic once bubbled...
...well cornfed......that level of accuracy is kinda cool for SAC experiments/measurements.......plus I just like it, there's no reason not to have the most accurate spg......just a personal preference......

Well Karl... I just played around with my log book and a 200 psi change in my ending pressure resulted change in my SAC rate of about 0.05 cfm... so I would say it doesn't matter.

and, apparently I'm not the only one that appreciates it...otherwise these products wouldn't exist.

There are a lot of things I appericate but that doesn't make them worth the extra money.

How much difference does 10psi make in your SAC calculations? Is it worth the extra money?

Cornfed

 

[JohnStrr]

Here's a digital pressure guage that can actually go underwater, hence the S in SPG:

http://66.129.98.69/Merchant2/merchant.mv?Screen=PROD&Product_Code=Gauge-Gas-E&Category_Code=GAGS

 

[cornfed]

JohnStrr once bubbled...
Here's a digital pressure guage that can actually go underwater, hence the S in SPG:

http://66.129.98.69/Merchant2/merchant.mv?Screen=PROD&Product_Code=Gauge-Gas-E&Category_Code=GAGS

<sarcasm>
And it's only $350!! What a deal!!!
</sarcasm>

 

[nickjb]

Uwatec make a digital SPG for about $100.

I'm not sure where analogue SPGs got their great reputation for reliability. There are countless stories of them going wrong and it is one of the few pieces of kit that I have had fail.

No moving parts or a bent bit of tube turning a tiny plastic gear wheel. Digital for me.

Nick

 

[Inkypoo]

DA Aquamaster once bubbled...
Not to sound too barnacle encrusted, but I did not even own an SPG for the first couple of years that I dove.

Wow....that must have been some time back.
Also how did people gauge the volume of air remaining in those days?

 

[DA Aquamaster]

Inkypoo once bubbled...


Wow....that must have been some time back.
Also how did people gauge the volume of air remaining in those days?

SPG's were recommended but using J-valves only was still pretty common. And with a well tuned unbalanced reg you could feel the subtle change in breathing resistance increase as the tank pressure dropped. With a J-valve you would feel the breathing resistance increase substantially as the valve started to close to conserve your reserve air supply.

In the worst case scenario the reserve lever got unknowingly pulled during the dive meaning the reg was breathing hard because you had already used the reserve and were just plain almost out of air. But even in that case, with an unbalanced reg you still had enough air remaining to surface (assuming no deco stops.)