Red zone on SPGs

[Rred]

What red marks?
I use one of the rare old Disney licensed Mickey Mouse SPGs. When Mickey's hands are both in his right side pants pocket, that means it is time to get out of the water.

I guess I should take one of those PADI Advanced Specialty Courses on "Using an SOG with Numbers On It." huh?

 

[KevinNM]

It would certainly be better if they had a bright needle against a darker background - wouldn't matter as much if the red zone had blended into the background then as you would still be able to tell the relative location of the needle

Like these ones from Dive Gear Express? Black Face Premium SPG, Naked | Dive Gear Express®

 

[NAM001]

I havnt seen any thing on paper but various thoughts via word of mouth, Gages if in error often have perhaps a 10% error noprmally in the lower end of the movement. for a 4k gage that is 400 psi. the reg needs 150 to breath so that brings the min presure to 550 with a 10% error. you can always compare you gage to the shops full presure but checking the lower presure is not so easy unless you check with another gage. Put your self at 100-130 ft and yo need another 50# to breath so the min of 200 psi at 100 feet to freely draw air and a gage error of 10% makes the 500 psi red line valid. I have also seen gages with red from 0-300 and yellow 300-500. also 500 psi is about what 14 cuft on an al80???? thats probably a reasonable min amount to start a safety stop if its accurate.

 

[Charles2]

If your gauge is in error of more than 2% of its span (i.e. 80 psi on a 4000 psi gauge), it should be replaced. After all, they are just not that expensive. That is my opinion only. I do check the calibration of my gauges annually and have only rarely replaced one.

 

[dmaziuk]

The tube behaves more or less like a spring: there's X amount of pressure between 0 and the point where it starts flexing, and as it flexes more it requires more effort to push. I expect that first bit is where "error at the lower end" thing comes from, and it's technically correct, but the real question is how much. A 15 psi error between 0 and 15 psi makes absolutely no difference to a scuba diver as you can't breathe that either way.