SPGs - 2" or 2.5", smaller scale vs larger scale...

Hi Everyone,

There is a proliferation of primary air SPGs, with sizes varying from less than 2", up to 2.5" in diameter, and scales ranging from 300 BAR, up to 450 BAR (4,400, up to 6,500 PSI).

Remember: [1.0 BAR] = [14.5 PSI] = [0.987 ATM = atmosphere at sea level]:
http://en.wikipedia.org/wiki/Bar_(unit)

Most SPGs for sale seem to be 2", with some 2.5" options, and I was wondering what people actually prefer and for what reason. Scubatoys had a massive 2.5" Highland SPG sale at some point and people were clamoring for this size.

I was about to purchase a Highland 2.5" SPG in BAR, because looking at a tape measure the 2" looks absolutely tiny. However, later looking at an actual 2" circle (rather than a tape measure) it seemed that this would not be too small.

It also seems that the Highland gauges have different faces on them when looking at the 2" vs the 2.5". Strangely, the 2" face has the ticks further towards the center of the dial, leaving more white area around the circumference. What gives with this difference? This just compresses the size of the typefaces because they have an even smaller arc to fit into.

I have also taken a look at Termo, who make a 300 BAR (4,400 PSI) scaled SPG that is about 1 3/4" in diameter. The scale is good. However, the gauge has both red and blue markings on it, which really become redundant very quickly I think. The Termo gauges also have plastic faces rather than glass, and one LDS said the glass faces have a tendency to crack, whereas the plastic faces tend to only scratch.

I have read about issues with Termo gauges. Mostly to do with leaking, even when close to new. Interestingly these seem to be made by the same company that makes OMS, OxyCheq, DR, Highland, Halcyon, etc. From this I can only assume that each company works with Termo independently to produce SPGs according to their own specific designs and standards.

So, what do people prefer about size and scales in their SPGs? What about plastic vs glass faces?

I was inclined to purchase a boot with the SPG and cut off the tail to expose the area where the hose attaches, but still protecting the SPG itself from shock damage (such as when it is flapping around out of the water. Thoughts on boots or the idea of cutting enough to expose the fittings?

If any of this seems to be just academic just chime in with that as well.

Cheers,
Nick

I prefer the smaller 2" ones...they're plenty big.....been using the Halcyon ones, incremented in units of 1000 psi, and sub-incremented in 100 psi intervals....but am also using Poseidon ones, with main increments each 500 psi, and sub-incremented in 250 psi intervals. My spg's are really just backups for my air-integrated computers.

I use rubber boots on mine, and prefer glass faces, the glass faces are WAY more resistant to scratching, and I suspect any blow strong enough to crack/smash glass would also shatter a plastic face.

I would go with a smaller simple gauge........

Easier to travel with, compact is good........no boot......keep it simple

Unless you are doing some very advanced to the limit diving (think deep cave exploration) I don't think having a more "detailed" SPG makes a lot of difference......

As long as it is a good solid brand and you take care if it.....no dropping, banging, etc.......then you are OK....

Good dive planning ensures you always have air......so the gauge is more of a simple confirmation of this.........

I like the 1.5 inch thin face mini gauge from dive gear express......

Submersible Pressure Gauges (SPGs) - Dive Gear Express

Hope this helps.........M

PS......assumes your eyes are OK, if vision is an issue I can see using a much larger gauge..........

Check out the HOG ones. They seem pretty reasonable in price.

EDIT: Thanks guys, for your above posts. Luckily I still have 20/20 vision.
EDIT: Yeah, Dive Gear Express DO have great technical detail about their products... often more than the Manufacturer provides... go figure.

Okay, here is something that has been bugging me. I can go to a "supposedly boutique" manufacturer like Mares and get detailed specifications on their Mission SPG. Including:

Mission Line
For increased legibility all the instruments are equipped with fluorescent dials. Special attention has been
devoted to the ergonomics of these consoles, as can be seen from their shape and the material used which, in addition to being highly
shock resistant, affords a secure grip in every situation and with any type of glove.
CE CERTIFICATION
The certification testing results are as follows:
Model and Marking
Submersible temperature and pressure gauge approved CE 0426
Submersible pressure gauge + hose approved CE 0426
EN 250: 2000 restrictions: maximum depth 50 m.
Instructions for use
- Never look directly at the instrument dial when opening the tank valve.
- Remove the thread protection cap before connecting the hose to the high pressure port of the regulator first stage.
- The 7/16" male thread of the hose must only be connected to the high pressure port of the regulator first stage.
- Do not manipulate the neoprene safety valve on the back of the case.
- To avoid trailing the submersible pressure gauge with hose, fasten it to your buoyancy compensator.
Accuracy
The guaranteed accuracy of the pressure measurement is:
at 50 bar ± 5 bar
at 100 bar ± 10 bar
at 200 bar ± 10 bar
at 300 bar ± 15 bar
Dial
Color: fluorescent light blue.
Diameter: 60 mm, 52 mm, 42 mm.
Case materials
- Nickel plated brass.
- Stainless steel.
- Tempered mineral glass.
Scale
Pressure gauge: 0 to 300 bar (0 to 5000 PSI) / 0 to 400 bar (0 to 5800 PSI) / 0 to 450 bar (0 to 6500 PSI).
- Never exceed the following values of input pressure to the submersible pressure gauge:
• 200 bar for a full scale value of 300 bar / 3000 PSI for full scale value of 5000 PSI.
• 300 bar for full scale values of 400 and 450 bar / 4500 PSI for full scale values of 5800 and 6600 PSI.
*The normal working pressure is indicated on the back of the case.

Click to expand...

and, if I go to some place like, say... Halcyon, I'll get:

Gauges
Halcyon pressure gauges are as reliable as they are accurate. We start with industrial-strength spring designed for pressures beyond 5,000psi (400BAR), high-quality materials, and a highly visible, luminescent face make this a common favorite among divers in all environments. Pick from our Standard or Stage pressure gauges.

The weight and size of our Standard SPG gauge make it well suited as a primary SPG; the large, clear display is easy to read in all diving conditions.
Key Features of the Standard SPG
Calibrated for BAR (0-360) or PSI (0-5000)
Nickel-plated brass with mineral glass lens.

Click to expand...

Interestingly, the non-technical oriented product give specifications that provide way more technical data. The distinct lack of available specification is something that appears to be common in "technical diving" product. And, I am perplexed... it's like, wtf?

Every technical diving product that is more complex than a webbing harness should have appropriately detailed specifications that can be viewed either on a webpage or as a downloadable PDF.

More than anything else, these days, it is information that distinguishes one product from another, and one competitor from another. Maybe Halcyon is just like all the "boutique" manufacturers, in that they want you to "feel good, feel trusting" of their products without "need to know" technical details.

Bit of a contradiction to the whole DIR/GUE technical approach, don't you think?

Here is a cool video about how pressure gauges are made:
YouTube - How Pressure Gauges are Made

A scuba SPG video (looks pretty old):
http://www.youtube.com/watch?v=djNB4Hluj1E

I prefer to travel light, and the 2" model is a good compromise.
If you want a SPG that doubles as a meat tenderizer, you will no doubt love the 2 1/2".

I would not say that Mares provides detailed specs......

They just do a better job of formatting standard information......

All the European SPG's are made to CE specs......most dive SPG's are made in Italy (I think?).......

The accuracy of about +/- 10% (5 bar at 50 bar) is "normal" for this price range of gauge....

It is interesting that Mares says no more that 3000 psi for a 5000 psi gauge....that seems like marketing hype......from my Navy days I recall guidance not to exceed 75% of the indicated range......so a 4000 psi gauge is good for up to 3000 psi......

In the Mares case if you have a 5000 psi gauge and you get an overfilled AL80 tank at 3100 psi (which happens) have you damaged the gauge? I think not.......

The dial and case material info - is again standard brass and glass SPG stuff.....

Hope this helps......M

I like the 2" brass and glass for deco/bailout bottles and the 2.5" for backgas. I prefer the glass to the acrylic lens.

As far as brands I don't really care as they are all about the same. The dial seems to be the major difference between them. I like the the clean simple white ones like the Highland or HOG's.

I would avoid the multi colored/BAR and PSI such as some of the OMS gauges. I dont like/need the colors or the scales on those.

Never found a need to put a protective rubber cover on them.

The majority of the Single SPG style gauge that we sell are the Highland 2". I find the 2.5" to be obnoxiously big but if someone has poor eye-site, then it becomes useful.