Training Guide in Surface Weather Observations - Multiple Choices

6.7.3 Reading and Setting the Minimum Thermometer
The minimum temperature is the reading at the right end of the index farthest from the bulb, not the
reading on the alcohol column (see Figure 6-7).
Part (a) of Figure 6-7 shows the top of the alcohol
column some distance to the right of the index. In
part (b), the alcohol column has retreated with
falling temperature until the top just touches the
index. Further cooling moves the bulb (to the
left). As the temperature rises again, the alcohol
column moves toward the right without moving
the index. Part (c) shows an incorrect reading with
the index trapped in the broken alcohol column.
6-10
Figure 6-7. Index on Minimum Thermometer.
Read the thermometer to the nearest 1/10 of a degree, before moving it from the almost horizontal
position in which it was set at the time of the last observation and before reading the maximum
thermometer.
To set the minimum thermometer, point the bulb end upward. Allow the index to fall to the end of the
alcohol column. Then turn the thermometer counterclockwise until it stops. The bulb end will now be
slightly lower than horizontal.
6.7.4 Reading and Setting the Maximum Thermometer
The highest temperature occurring since the maximum temperature was previously set is the reading at
the top of the mercury column, taken with the bulb end lowered. Carefully release the support catch
back of the clamp and lower the bulb end of the thermometer slowly until the thermometer is vertical
and the mercury column is resting on the constriction. Stand as far from the thermometer as possible
to prevent body heat from changing the readings. Do not touch the bulb of the thermometer.
Be sure that the line of sight from your eye to the top of the mercury column is level to avoid parallax
error (see Figure 6-8) and read the temperature to the nearest 1/10 of a degree.