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205 215 225
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Figure 31. Tests of Olle.nd-c~·cle performance.
Hysteresis at any one temperature was the worst serious cause
of the width of the envelope of curves. However, this
error was minimized by the smoothness of the rotating cylinder
and the continuous motion of the cylinder under the contact
pen. Probably the necessary looseness of the bearings and
the joining to the motor gear train had a great deal to do with
the spread between different calib~ations.
The maximum variation of any one ce.libration curve from the
mean was about ~3 millibars.
The following recommendations are made for the use of the
Olland-cycle modulator:
(a) The modulator should be mounted inside the battery box and
insulated so as to keep its temperature above -30°C.
(b) During the rapid~rising portion of the flight the accuracy
of the data warrants reading only to the nearest one percent
of a cycle, or about one millibar of pressure.
Tests on the sensitivity of Olland-Cycle modulators indi-
cate that although the accuracy is li~ited as indicated
above, small variations may be detected with the result
that it is valid to read the pressure record to the nearest
tenth of one percent of one revolution.
-'71-