Figure 2-23.—Marine barograph chart.
ink is hygroscopic and will absorb moisture from the
air. When the ink becomes too diluted from absorbed
moisture, the trace will appear “washed-out.” When
this happens, remove the pen tip, rinse it in freshwater,
blow it dry, replace it on the pen arm, and reink the pen.
A wide pen trace indicates a dirty or damaged pen tip.
Clean and reink or replace the tip as appropriate.
Accuracy Checks and Adjustments
Time and pressure checks are completed at each
synoptic and intermediate synoptic hour, after reading
the 3-hour pressure tendency. At synoptic observation
times, touch the pen arm lightly to make a "tic" mark in
the pressure trace for time checks. Time adjustments
are required when the time is in error by 15 minutes or
more, and pressure adjustments are recommended
when the pressure is off by 1.5 hPa or more.
TIME ADJUSTMENTS.—Time adjustments are
made by rotating the chart cylinder until the pen is
marking at the correct time. A time correction entry
should be made on the chart, consisting of an arrow
pointing to the corrected time, the remark "Time Reset,"
and the correct UTC time, such as 1155Z. Remarks may
be made directly on the mounted chart or entered on a
note pad or clipboard near the barograph. If the remarks
aren’t made directly on the chart, they should be
transferred to the chart after it is removed.
PRESSURE ADJUSTMENTS.—Pressure
adjustments are made by turning the adjustment knob.
Draw an arrow to the correct pressure and enter the
remark "Pres. Reset," along with the UTC time, on the
chart.
Q19.
Q20.
Q21.
Q22.
Q23.
Q24.
Q25.
REVIEW QUESTIONS
How often should the aneroid barometer be
calibrated?
What procedure should you use to obtain a
reading from an aneroid barometer?
In what situation should the altimeter setting of
the DASI not be used?
What device enables the marine barograph to
maintain its precision aboard ship?
When should the chart on the marine barograph
be replaced, and what time should it be
coordinated with?
Rewinding the clock of the marine barograph
requires approximately how many pulls if
completed after every fourth day.
What criteria is used for time and pressure
adjustments on the marine barograph?
2-17
