There is a console attached to your regulator first stage with a high pressure hose. It is high pressure (first stage doesn’t decrease the pressure coming from the tank), because you have to see the actual values on your gauges.
By default, there must be two gauges on your console.
As you can guess easily, a depth gauge displays the depth. The needle (usually black) in it shows the actual depth you are diving. If you are on the surface, mounting your scuba, it points 0 meters.
There is another needle (in some models it is red, in others it is black but much more thinner than the other) always positioned above the other one. This needle gives you the information of the deepest point you have been in your last dive. You can set this needle manually to the 0 meters again before each dive.
Here is the logic:
- You set the red (or the one above the other) needle to 0 meters manually when you are getting prepared for your dive. Both needles are pointing 0 meters now. When you start your dive and go deeper, both of them starts to move and gives you the depth information.
- Let’s assume that you dove to 20 meters. Both needles point 20 meters there. But when you start to ascent, black needle starts to move backwards, but the red one (or the thinner one) freezes pointing the 20 meters.
- After your dive, you check your depth gauge and see that your deepest point for this dive was 20 meters.
Submersible Pressure Gauge (SPG)
SPG is the most important information gear. If shows you how much air you got in your dive tank. If we speak technically, it shows us the pressure of the air in our dive tanks.
In a standard dive tank, there is 200 atm/bar (3000 psi) pressured air. Using your air underwater, this pressure decreases because the air inside the tank decreases.
You dive leader will ask for your air during your dive and want you to check your SPG. You’ll tell (actually show by using some hand signals) how much air you got left (read 10 Golden Rules for Scuba Diving).
Majority of the manufacturers produce SPGs red coloring the 0 atm/bar or psi – 35 atm/bar (525 psi) interval. This is just like the warning red light in our cars. Our SPGs warn us. It doesn’t mean that you are out-of-air, but means that you are low on air.
I advise you to buy gauges with:
- Number format you used to (imperial/metric)
- Large fonts to read it easily
- a compass also (a 3 gauges console instead of the default 2). Don’t carry an external compass. More separated equipment, more attention.