2
DIVE MODE:
Whether in the Surface Interval, PreDive Prediction Mode, Programming
Mode or the Logbook Mode, the EMC-20H will automatically enter the
Dive Mode whenever the unit determines that it is in water deeper than
five feet.
On the Display Screen the Surface time will be replaced with the current
Depth and be displayed in one-foot increments. The maximum specified
depth is 427 feet, but the unit will continue to measure and display depths
deeper that that. A Depth Sensor warning will be issued (See later
discussion on Sensor Warnings) when the unit can no longer accurately
measure depth.
A Depth Alarm, which can be set to warn the diver should a certain depth
be exceeded, is set at 130 feet from the factory. The Depth Alarm issues
an audible alarm and the “WARNING” legend and Depth Digits will flash
on and off for five seconds. The depth alarm is disabled if in the
Decompression Mode since flashing depth digits have another meaning
in this Mode.
The maximum depth achieved on the current dive is shown as “MAX
DEPTH”. This is updated once per second.
“REMAIN TIME” (NDC) is the remaining time (in hours and minutes) that
the diver can stay at the current depth without requiring decompression.
A “Two Minute Warning” will be issued when this time reaches two
minutes or less. An audible alarm will be issued and the “WARNING”
legend and “REMAIN TIME” digits will flash. By immediately ascending
to a shallower depth, the diver may avoid a required decompression stop.
Temperature is measured for two purposes. One is to compensate the
Depth Transducer for Temperature variations. The other is to
compensate the Nitrogen algorithm for changes in Temperature that may
affect the body. Both of these purposes require that the Temperature be
very slow reacting, just like the Depth Transducer and the body. This
slow-reacting Temperature is what is displayed. For Temperature effects
on the body, the amount of compensation can be set from NORMAL to
REDUCED with the Analyst
®
PC software Interface (see Analyst
®
Section), if the diver is using a good dry-suit in cold water. Temperature
compensation starts at 75 degrees F and gets progressively more
conservative as the temperature decreases. There is no compensation
above 75 degrees F.
Bottom Time will begin once the EMC-20H senses that the diver has
descended below five feet (see Training Mode) and continues until the
diver has ascended above three feet. The maximum Bottom Time
displayed is 9 hours 59 minutes.
ASCENT RATE BAR GRAPH:
The Ascent Rate bar graph and alarms are active in both the Dive Mode
and Decompression Mode. The five-segment bar graph is used to
display the diver's rate of ascent.
Via the Analyst
®
PC Interface, the Ascent Rate Alarms and Bar Graph
can be set to the users preferences.
The first option is a VARIABLE-BY-DEPTH Ascent Rate. When on, the
Ascent Rate Alarm is determined by depth. As the diver ascends to
shallow depths, the Maximum Ascent Rate is lowered. The Maximum
Ascent Rates and their associated depth are:
60 feet or deeper 60 feet per minute
60 to 30 feet feet per minute equal to the depth
Less than 30 feet 30 feet per minute
If VARIABLE-BY-DEPTH is off, the Maximum Ascent Rate Alarm and Bar
Graph is specified by the user and can be from 20 to 60 fpm, in one foot
increments.
Another selection is the bar graph itself. The two selections are either
FIXED or PROPORTIONAL.
With FIXED, each of the five bars indicates an additional 10 feet per
minute of Ascent Rate regardless of the Maximum Ascent Rate selected.
With PROPORTIONAL, each of the five bars indicates 20% (one-fifth) of
the selected Maximum Ascent Rate.
For FIXED, the maximum ascent rate is 60 feet per minute. With this
setting, no bars will illuminate if a diver is ascending at a rate less than 10
feet per minute.
If the diver has an Ascent Rate that exceeds the selected maximum, the
entire Ascent Rate Bar Graph will flash, and the audible alarm will sound
once per second, and the WARNING legend will illuminate.
The sensitivity or responsiveness of the Ascent Rate may be selected via
the Analyst
®
, eight different levels of sensitivity are available.
NOTE: Customizing the Ascent Rate and Ascent Rate Bar Graph are
among many of the additional programmable features available when
using the Analyst
®
PC Interface. Available features are described in the
section “USER CONFIGURABLE OPTIONS”.
As shipped from the factory, the Ascent Rate is set for VARIABLE-BY-
DEPTH AND PROPORTIONAL.
DECOMPRESSION MODE:
Should a no-decompression limit be overstayed, the EMC-20H will enter
the Decompression Mode. In this mode, the Ceiling digits will display the
depth at which the diver must stop and not ascend above during final
ascent. The “TEMP” legend and two digits will be replaced with the
“CEIL” legend and two digits. The Ceiling will start at 10 feet and
increase in ten-foot increments as the diver remains at a relatively deep
depth.
The Remaining No-decompression Time and “NDC” legend will be
replaced with Decompression Time and “DEC” legend (Figure 16d). Both
STOP time and TOTAL time are displayed in the upper left hand three
digits of the screen in hours and minutes. STOP and TOTAL time will
alternate at the rate of once every two seconds. In this way, the diver
can view the time to spend at a particular STOP depth, and the TOTAL
time it will take to complete all STOPS. Clearly, the larger of the two
alternating numbers is the Total Decompression Time of all stops, and
the smaller of the two numbers is the time required at the current stop. At
the ten-foot stop, the TOTAL and STOP times may be the same and
therefore appear to not alternate.
When at a specific stop, the required decompression time at that stop is
as shown, and will appear to count down as it is recomputed every
second, based on the divers exact current depth. The Decompression
times (both Stop and Total) are accurate only if the divers depth is exactly
the same as the required Ceiling. However, it is not necessary to be
precisely at that specified Ceiling. Appropriate In-gassing or Out-gassing
will be computed regardless of the divers current depth.
A small margin shallower than the Ceiling also exists. Should a Ceiling
be ‘violated’ (diver is shallower than Ceiling), the “WARNING” legend will
illuminate and flash along with the Depth and Ceiling digits. An Audible
alarm will sound once every two seconds. This warning will continue until
the Depth has been corrected. Out-gassing will continue even though the
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