HOG SPG (BAR) Labelling Error?

[buddhasummer]

cerich:

Just curious, do the HOG gauges use Bourdon Tube or Helicoid elements?

Bourdon I believe. Pinned.

 

[victorzamora]

i didn't understand the reason.. What is the exact reason for less marked between 50 to 0 Bars than the other parts of spg? does it wanted to be more accurate?

This is what you're missing. There IS NO ZERO on an SPG. The "peg" that markes "empty" is actually showing about 10Bar. If you have less than 10bar, it'll still just show 10bar. Since 10bar is not a lot of air, and you should be coming up with more air than that anyway, it doesn't matter if you have 6bar or 7bar.....your tank is empty according to your SPG. Since the difference between 6bar and 7bar is completely unimportant in terms of reading an SPG, they made the "accurate region" of the gauge higher, where the pressure DOES matter and just pegged the SPG at a minimum of 10bar. It's extremely costly to get an SPG that will actually read zero accurately AND read high pressures accurately, so they just circumvented the cost by pegging it at 10bar.

 

[lowviz]

...//... What is the exact reason for less marked between 50 to 0 Bars than the other parts of spg? does it wanted to be more accurate?

No. Imagine a gauge with the correct number of tic marks between 50 and zero. Now erase zero and put a pin at ten so the needle cannot drop below ten. Re-label ten as "ZERO". That is all that they did. It would have been better to remove ALL the tic marks between 50 and zero (ten, actually).

Exactly what do those final divisions mean to you while you are diving? It is an analog gauge, you just glance at it and get your current gas situation.

 

[Akimbo]

A lot of this is assuming that one increment is significant in terms of accuracy. Like typical small industrial gauges, most SPGs are “supposed” to be accurate to +/- 2½% of the overall range in the mid third scale. Ten Bars is just a rounding error at the low or high end.

AI (Air Integrated) computers are typically much more accurate, but slow responding. They often average signals over 5-10 seconds and round to 10 PSI or 1 Bar depending on the units.

New Subject
The attached image is an old Oceanic SPG that uses a direct-drive helical pressure sensing mechanism rather than a typical geared Bourdon Tube.

 

[John_B]

Exactly what do those final divisions mean to you while you are diving? It is an analog gauge, you just glance at it and get your current gas situation.

A lot of this is assuming that one increment is significant in terms of accuracy. Like typical small industrial gauges, most SPGs are “supposed” to be accurate to +/- 2½% of the overall range in the mid third scale. Ten Bars is just a rounding error at the low or high end.

AI (Air Integrated) computers are typically much more accurate, but slow responding. They often average signals over 5-10 seconds and round to 10 PSI or 1 Bar depending on the units.

Are digital gauges any more accurate, or do they just show greater precision?

 

[Akimbo]

Are digital gauges any more accurate, or do they just show greater precision?

My understanding is the sensors in most AI computers are +/ ¼ to 1% accurate over the full range. Of course averaging and rounding obscures some that precision, though it keeps the display from constantly cycling the digits.