Shearwater TERN - Page 17

Operating Instructions
Page 17
Doc. 15301-RevB (2023-11-24)
m
min
GF
35/75
GF99
22
%
136
%
SurfGF
SURFACE
m
min
GF
35/75
GF99
22
%
15
TTS
SURFACE
m
min
GF
35/75
GF99
22
%
15
TTS
SURFACE
Gradient Factor
The deco conservatism value when
the deco model is set to GF� The low
and high gradient factors control
the conservatism of the Bühlmann
GF algorithm� See “Clearing up the
Confusion About Deep Stops” by
Erik Baker for more information�
GF99
The current gradient factor as a
percentage (i�e� super-saturation
percent gradient)
0% means the leading tissue super-saturation is equal
to ambient pressure� Displays “On Gas” when tissue
tension is less than the inspired inert gas pressure�
100% means the leading tissue super-saturation is
equal to the original M-Value limit in the Bühlmann
ZHL-16C model�
GF99 is displayed in Yellow when the current gradient
factor modified M-Value (GF High) is exceeded�
GF99 is displayed in Red when 100% (un-modified
M-Value) is exceeded�
Time-To-Surface (TTS)
The time-to-surface in minutes� This
is the current time to ascend to the
surface including the ascent plus
all required deco stops and safety
stops�
Temperature
The current temperature in degrees
Celsius or degrees Fahrenheit�
Temperature units can be set in the
Display settings menu�
Battery
The Tern’s remaining battery level
expressed as a percentage�
Displays in yellow when battery is low and needs to
be recharged� Displays in red when battery is critically
low and must be recharged immediately�
Pressure
The pressure in millibars� Two values are shown,
the surface (surf) pressure and the current (now)
pressure�
Note that typical pressure at sea level is 1013 millibar,
although it may vary with the weather (barometric
pressure)� For example, in a low pressure system
surface pressure may be as low as 980 millibar, or as
high as 1040 millibar in a high pressure system�
For this reason, the PPO2 displayed on the surface
may not exactly match the FO2 (fraction of O2),
although the displayed PPO2 is still correct�
The surface pressure is set based on the lowest
pressure the Tern sees in the 10 minutes prior to the
start of a dive� Therefore, altitude is automatically
accounted for and no special altitude setting is
required�
TEMP
21 49
BATTERY
%
�C
m
min
SURFACE
TEMP
21 49
BATTERY
%
�C
m
min
SURFACE
mBar SURF
1013
mBar NOW
4943
m
min
SURFACE