SPG gauge has only 4 notches between 0 and 50 bar

[BlueTrin]

Just notice that some SPGs have only 4 notches under 50 bar.

Is that because under 10bar is not considered as reliable ?

For example:
- Halcyon Standard SPG
- Apeks Tek SPG

 

[1atm]

Short answer: yes. Depending on what you are trying to do, anything less than 40 bar could be called inaccurate (eg minimum gas).

 

[Ayisha]

Under about 30 - 40 bar is considered unreliable.

 

[1atm]

Once you are out of the water, there also is another aspect: generally you should try to avoid draining a tank completely. If you always maintain a little pressure (say 20 bar), you can be sure that the tank stays clean, and no water, oil, dirt or whatever gets inside. Some fill stations may refuse to fill totally empty tanks, especially when partial pressure blending (eg for Nitrox).

 

[Charles2]

Analog pressure gauge accuracy is generally given in % of full scale accuracy. A very good gauge might have an accuracy of 2%. I don't know the manufacturer's accuracy of the gauges you listed; however, if they are 2%, that means that they are ±7.2 bar at any point on the scale. 7.2 bar may not seem like much error when you have over 200 bar in the tank, but it is a lot of error when you get below 50 bar.

 

[Bob DBF]

Looking at SPGs in both bar and psi, I could find no standard in use. Highland Millworks Miflex Gauge Shows 10 bar incraments instead of 12.25 bar increments. I'm assuming since it is a pressure gauge they should be marking it accurately, whether it could be off or not. On some gauges I've seen there are no markings from 50 bar, or 500 psi on imperial, to zero.

I guess it's to not encourage divers to do gas planning below the established minimum as it could turn out badly. In addition, if you are supposed to be on the surface at 500#, you don't need any indication below that. Or it's just cheaper to leave it off.


Bob

 

[clownfishsydney]

Mine is the same, as far as I can figure out, 10 bar is when it is hard against the stopper pin. Sort of gives a safety margin.

 

[BlueTrin]

Mine is the same, as far as I can figure out, 10 bar is when it is hard against the stopper pin. Sort of gives a safety margin.

I hope you never had to use this 'safety margin'

 

[Gareth J]

Mine is the same, as far as I can figure out, 10 bar is when it is hard against the stopper pin. Sort of gives a safety margin.

I think you are over optimistic if you think its a safety margin.
I've seen contents gauges showing 20 or 30 bar........ not even connected to a cylinder......

 

[clownfishsydney]

From experience I can assure you it is a safety margin (in 3 metres of water so perfectly safe).