sure in whole millibars. While the range of the millibar scale is from

1 0 85 to 745 millibars, these barometers are calibrated only to 1066.7

millibars (or 31.5 inches). This does not mean that higher pressure

readings will be inaccurate, but only that the accuracy has not been

checked above 1066.7 millibars.

(2) In covering the range of the millibar scale, the pointer makes

almost two revolutions of the dial. Unlike the inch scale, the same

scale is not used on the second revolution of the pointer. Pressures

b e t w e e n 108 5 and 895 millibars are read on the center scale, while

pressures between 895 and 745 millibars are read on the inside scale.

(3) The millibar scales are graduated in whole millibars and esti-

mated readings may be made to a tenth of a millibar.

The reading on the inner scale is 81 1.8 millibars.

ter ML-1 0 2-B or ML-1 0 2-F is the station pressure.

(2) The pressure, as read on the dial of Barometer ML-102 -E must

be corrected for temperature (see par. 11 below) before the station

pressure is obtained.

reading. Barometers ML-102 -B and ML-102 -F are equally affected by temperature

but temperature correction charts were not required, hence pressure data obtained

from these two barometers generally will not be as accurate as that obtained from

B a r o m e t e r s ML- 102-E, ML-102-D and ML-316/ T M .

B a r o m e t e r ML- 1 0 2-E has been determined by actual test for each

instrument and the corrections are shown in the form of curves on

the temperature calibration chart fastened to the back of each instru-

ment (fig. 5 ) . These curves also include a small residual error for

each instrument (par. 1 5 C (2 ) ) .

one for a temperature of 80 F., another for 40 F., and a third for

o F. These curves are plotted on a grid on which the pressure is

shown on the horizontal scale and the corrections on the vertical scale.

(2) To compute the temperature correction, determine the tem-

perature to which the barometer has been exposed and locate the

temperature curve nearest to that temperature.

(3) Find the indicated pressure on the horizontal scale. Move ver-

tically until the pressure value meets the correction curve. From the

point on the correction curve move horizontally to the left until the

correction scale is encountered. If the pressure reading does not meet

the temperature correction curve on a horizontal line, it will be nec-

essary to estimate between the two tabulated correction values. Deter-

mine the correction at that point, noting whether it is plus or minus.

(.4) Add or subtract this sum to the observed pressure reading.

1 hours before making a reading.

the values for which correction curves are given, the corrections must

be determined for both curves and the true correction by interpolation.

Integrated Publishing, Inc. |