1. Gauge Pressure

2. Objectives Describe gauge pressure. Correctly calculate the gauge pressure for a given depth of either fresh or salt water. Apply the concept of gauge pressure to scuba.

3. Main Points Gauge pressure Calculating gauge pressure Application to scuba

4. Description Uses atmospheric pressure as zero.

5. Example 1 Calculate gauge pressure at 57' of fresh water. Answer: (.432psi/ft) x 57' = 24.6 psig Convert the answer above to absolute pressure. Answer: 24.6psi + 14.7psi = 39.3psia

6. Example 2 Calculate gauge pressure at 57' of salt water. Answer: (.445psi/ft) x 57' = 25.365 psig Convert the answer above to absolute pressure. Answer: 25.365psi + 14.7psi = 40.065psia

7. Application to Scuba The concept of gauge pressure explains why an analog depth gauge will not give an accurate reading of depth when diving at altitude. Care to explain? –An analog depth gauge uses 14.7 psi as 0 ft – at altitude you must dive to some depth before you reach a pressure of 14.7 psi

8. Main Points Gauge pressure Calculating gauge pressure Application to scuba

9. Objectives Describe gauge pressure. Correctly calculate the gauge pressure for a given depth of either fresh or salt water. Apply the concept of gauge pressure to scuba.