Analog SPG inaccuracy

[Scared Silly]

True, consistency or consistent as in unchanging over time. All things being equal, does the measurement remain the same?

The other I would put under the reliable category.

 

[onfloat]

@Onfloat:
You appear to have some experience with analog spgs. What brand analog spgs do you sell at your scuba shop? What manufacturer produces that brand? And what are the accuracy specs on those gauges as reported by the manufacturer? For the sake of the OP, it might be useful comparison info. Thanks in advance for the info.

Well, I do have experience with analog gauges, from my career in avaition. I also ran a calibration lab for a while. Scared Silly did an excellent job of breaking it down. Another thing to be aware of is temp and age (amount of use) can affect any bourdon tube gauge.

I guess you haven't clicked on the link in my signature, because you would see that I'm not currently selling any SPGs. I am working on it though. The ones that I'm looking at carrying are made by the same company that makes SPGs for Halcyon. Strangely enough it's tough to find the specs on these things. Although I did ask and have my supplier looking in to it.

Heck, I never even thought about it before this thread. I always just assumed the gauge was an approximation of the pressure and never trusted it once it was below 500 psi. After awhile of using it I would know how far the needle is supposed to move and go from there.

 

[tagline]

I took the following from Suunto's Mechanical Instrument Manual.
http://www.aqualung.com/technical_library/Combo_manual_en_2e279.pdf
The tolerance for pressure guages, measured at decreasing pressure are:

At 40 Bar +/- 5 bar
At 100 Bar +/- 10 bar
At 200 Bar +/- 10 bar
At 300 Bar +/- 10 bar

1 Bar = 14.5 psi
5 Bar = 72.5 psi
10 Bar = 145.0 psi

So there a tolerance of +/- 200 psi all the way down until you get close to 600 psi and then the tolerance drops to approx. 75 psi +/-

 

[Bubbletrubble]

I finally got around to viewing all of the recent posts.

Thanks for the info, Tagline, Onfloat, and Scared_Silly. I suspect the OP will stick with using his SPG...for now. I hope that when the shop calibrates the instrument, the technician will check the accuracy and precision at several different values (going up as well as going down). As long as the instrument remains reliable and consistent, there shouldn't be a safety issue.

Thanks once again for chiming in with the great info, guys.