18
Air Time Remaining (ATR) - integrated model PDCs only
ATR is the time you can remain at your present depth and still surface with the tank pres-
sure reserve (End Gas Alarm Set Point) that you set prior to the dive.
ATR is calculated using a patented algorithm that is based on the diver's individual air
consumption rate and depth. Tank pressure is measured once each second and an aver-
age rate of consumption is calculated over a 90 second period. This rate of consumption
is then used in conjunction with a knowledge of the depth dependence to predict the air
required for a safe ascent including any required decompression stops.
ATR will fluctuate throughout your dive, decreasing as you dive deeper or breath heavier,
and increasing as you ascend to shallower depths or relax your breathing efforts.
Since air consumption and depth are continuously monitored, ATR reflects any change in
your circumstances, such as when a buddy starts breathing from your octopus or you swim
against a strong current and begin breathing more rapidly. The PDC will recognize this
change and adjust ATR as required.
Depending on the conguration of your model PDC, ATR may be displayed on
the Main Dive screen* together with NDC, as DTR in place of NDC, or only on
an Alternate Display accessed for several seconds.
*During Deco, ATR may be moved from the Main to an Alternate screen to allow the space on the
Main to be used for more critical information.
(continued on page 19)
