IBIS? INSPECTING AND TESTING THE RADIOSONDE 
markings are properly aligned. If the numbers and markings are im- 
properly aligned to the extent that uncertainty exists about which value 
corresponds to a given set of markings, reject the radiosonde. Four 
types of pressure calibration charts are used. The following subsections 
describe these charts. 
1.1.1 A long strip-chart containing two scales (see Fig. Bl-1). The 
scale on the left shows the pressure in millibars and is marked in two- 
millibar increments. Each 10 mb increment is indicated by a wider 
mark. Numbers denoting 50 mb increments are printed to the left of 
every fifth ten-millibar mark. The scale on the right is the ''contacts" 
scale, A calibration dash for the ''make" of every metallic segment of 
the commutator is superimposed on the pressure scale. The contact 
number is printed every fifth contact. For evaluation purposes, the 
bottom edge of the dashed calibration line is used for reading the pres- 
sure value. For evaluation of partial contacts, linear interpolation is 
necessary between the bottom edges of the calibration dash preceding 
and succeeding the partial contact. 
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Figure B1-1. Strip-Type Calibration Chart (Two- Mb Increments) 
P69 FMH#3 
