of the motor-driven units was observed; current practice is to provide adequate temperature insulation.
(4) Barograph
As a secondary pressure unit, a clock-driven barograph has been included on many flights. The instrument (shown in Figure 33)
[figure]
Figure 33. Smoked drum barograph.
will provide up to 40 hours of pressure data if recovered. About 70% of all those units flown to date have been recovered. The performance specifications are as follows:
(a) Rotation: one revolution every 12 hours
(b) Duration: 36 hours running time
(c) Pressure range: 500 to 5 mb.
(d) Accuracy: ±5 mb.
(e) Readability: 1.0 mb. or approximately .22 mm on the drum
(f) Weight: 1000 grams
(g) Time accuracy: 10%
(h) Temperature compensation between 30°C and -70°C
Instruments have been built by Lange Laboratories to meet these requirements (the time accuracy figure is questionable).
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