Underwater, you need additional instruments to give you vital information. That information includes the following.
- Maximum depth reached
- Current depth
- Time spent underwater
- Current gas pressure in the cylinders
- Partial pressure of oxygen (for rebreather divers)
All this information can be obtained from various instruments or from your PDC.
What Is Partial Pressure (pp)?
Pressure is made up of the sum or total of partial pressures. For example, the pressure of air/gas at sea level is 1 bar/ata, and it is made up of 0.21 oxygen (21%) plus 0.79 nitrogen (78% N2 +1% inert gas). So, the partial pressure of oxygen is 0.21.