SPG accuracy

[iain/hsm]

Very interesting post! Is there an equivalent US standard to EN837-1? I can't seem to find any SPGs sold here which meet this standard, so I wonder if another one is used.

Yes for the USA spec try ASME B40.1 They have four grades
4A 0.1%
3A 0.25%
2A 0.5%
1A 1%

All the above grades are equal in both the lower 1/4 of the scale, the mid range 1/2 of the scale and also the upper 1/4 of the full scale

Once you go into the scuba junk market and the made for profit and retail margins
So the standards are progressively poor.

Again using ASME B40.1 the standards lower than the A class there are graded from A to D and this is where the scale drifts out over the full scale deflection.
Again measured of the lower 1/4 midrange half and upper 1/4 of the scale as follows:

A is 2% 1% and 2%
B is 3% 2% and 3%
C is 4% 3% and 4%
D is 5% 5% and 5%

I guess now you know why the scuba suppliers don't quote you the accuracy.
The DEMA trade body standard is below D Iain Middlebrook

---------- Post added April 14th, 2015 at 05:33 PM ----------

Very interesting post! Is there an equivalent US standard to EN837-1? I can't seem to find any SPGs sold here which meet this standard, so I wonder if another one is used.

Its interesting to look at the description of these scuba submersible gauges from various scuba web sites as an example .


1. Halcyon state on there web site that the key feature of there gauge is that it is calibrated for BAR and PSI This is nonsense its not calibrated at all.


The term is “graduated” not calibrated. Halcyon are totally obscuring the valid fact of calibration

http://www.halcyon.net/essentials/SPG

2. Scubapro state similar nonsense in the sales stuff but do have a pdf that discloses accuracy if you dig around


http://www.scubapro.com/media/267298/scubapro_instruments.pdf


Its 10% in the first 1/4 scale, 10% in the mid range and 5% in the upper 1/4 scale
Hopelessly so out of anything resembling a gauge almost akin to a wild guess
It doesn’t even come close to the lowest standard of ASME B40.1 grade D


3. Aqualung: state the submersible pressure contents gauge with an internal Bourdon pressure measuring mechanism, gives you clear information on the gas content of your cylinder?


https://www.aqualung.com/us/gear/leisure-divers/item/246-apeks-spg-brass-5000psi#tab17


Again a total misdirect………..clear information? means you can see it nothing more and nothing to do with accuracy

 

[NAM001]

When possible i ask hte filler what the tank pressure was in the tank before filling. That way i know whether my spg is in agreement or possibly off.

 

[RJP]

When possible i ask hte filler what the tank pressure was in the tank before filling. That way i know whether my spg is in agreement or possibly off.

...or if their's is off.

A man with one watch knows exactly what time it is. A man with two watches is never really sure.