Training Guide in Surface Weather Observations - Multiple Choices

g. Press and hold the “MAX” and “MIN” buttons simultaneously to test the fluorescent display
for missing segments. All segments that are not already illuminated will flash intermittently.
h. The message “LO” or “HI” may appear indicating an open or shorted sensor or, less likely, a
temperature colder than 55°F or hotter than +125°F.
6.9.2 Operation
The current temperature is displayed if no buttons are pressed.
Depress the “MAX” button to display the maximum temperature that occurred since the MMTS was last
reset. Depress the “MIN” button to do the same for the minimum temperature.
Simultaneously press the “RESET” and “MAX” buttons to reset the stored maximum temperature. Do
the same with the “RESET” and “MIN” buttons to reset the minimum temperature.
Do not reset the maximum or minimum temperature between the scheduled times of observation.
Resetting at unscheduled times is the most frequent cause of errors.
Record the maximum and minimum temperatures to the tenth of degrees Celsius even though the
readings are displayed to the nearest tenth degree Fahrenheit.
6.9.3 “HELP” and Blinking Displays
If the “HELP” message appears on the display, press the “RESET” button to clear it and to show the
current temperature. “HELP” indicates that an interruption to the A.C. line voltage has occurred. The
microcomputer enters a “power down” condition in which the internal backup battery is used to preserve
the maximum and minimum values stored in memory. These values are stored up to two hours without
power. However, no updating of new maximum and minimum temperatures occurs during or after the
power interruption until the “RESET” button has been pressed.
6-16