SPG accuracy question

[northernone]

I figure a SPG to read an approximate when full - + a couple hundred psi.

That's nothing down there worth cutting gas planning that close and as long as the needle doesn't stick or show 1000 psi when empty, I don't mind or expect more.

Cameron

 

[divinh]

On a related note(?), I've noticed that SPG's read different on the surface than when right after getting in the water, a swing of 20-30 bar. For air consumption calculations, which one is used, surface or in the water? I generally look at the SPG right before turning off the air after a dive, if that matters.

 

[MaxBottomtime]

The tank could be warm on the surface, increasing pressure.
I had a SPG that was pretty far off. I was in shallow water near the end of a dive. Merry had a lot of air left (she always does) so I told her I would follow her from above and surface when the tank was low. The needle was touching the pin at 200 psi for another twenty minutes. I surfaced before it became hard to breathe so I don't know how long I could have used that tank.

 

[cerich]

Is your depth gauge set to EN13319?

what are you talking about? That is the CE stadard for dive computers rearding fresh and salt switch. The depth gauge doesn't have that.

The gauge is CE , it's made by Termo in Italy, same as many brands.

As some posters have said, exact accuracy in them is not common, however they should be within a small range.

Anyhow, be happy to exchange the spg.

 

[dmaziuk]

what are you talking about? That is the CE stadard for dive computers rearding fresh and salt switch. The depth gauge doesn't have that.

:sigh: not funny when you have to explain: poster's depth gauge did not match the computer. The computer may be set to the CE standard, what standard is the depth gauge set to?

 

[JamesBon92007]

Is your depth gauge set to EN13319?

I'm sure I set it for salt water.

 

[cerich]

:sigh: not funny when you have to explain: poster's depth gauge did not match the computer. The computer may be set to the CE standard, what standard is the depth gauge set to?

ok, the deep 6 SPG measures pressure, the "depth gauge" has nothing to do with it.

 

[txgoose]

Really like my Deep 6 first stage. No experience with their SPGs. As others have said, SPGs havin some variance probably isn’t unusual. But, you’re the one using it and you’re allowed to get the one you feel most comfortable with. Below is a link to another thread about AI and SPGs. I did an SPG test of sorts. Not an AI test.

SPG or AI, Who’s Right?

 

[scrane]

Practically speaking, you can determine the offset at full tank and at 500psi. If there is little offset at 500 I wouldn't bother swapping it out.

 

[JamesBon92007]

FWIW I have several SPGs and most of them will read within, say, about 50 psi on any given tank (I compared them in the past, on one tank that was full). I have one that reads about 100 psi lower. I suppose lower is better than higher

One of my SPGs is very old (US Divers, probably from the 60s). I had just replaced the O-rings and was checking it for leaks and I also wanted to determine if it was still accurate, plus I had a leaky tank valve so I needed to empty the tank. I decided to suck it dry in my swimming pool. It began getting harder to breathe from when the SPG indicated about 135-140 psi which is the IP pressure for this particular regulator. To me that indicates that the SPG is reasonably accurate. If anyone is interested, I managed to continue to breathe from the tank for four minutes at six feet before there was nothing left.