ANALOG EQUIPMENT FOR PROCESSING RANDOMLY FLUCTUATING DATA 



347 



Wind + unnel or 

 Ground Test 

 Facility Data 



RocUet Model or 

 Airplane Data 



Data Recorded 

 on Film 



Loop 



FM. 

 Modulators 



1 _ FM. Radio 

 J Telemeter 



FM.^ 

 Transcriber 



JPPlayback 



FM. 

 Demodulators 



Multichannel 

 Magnetic 



Tape 

 Recorders 



Distribution 

 Analyier 



> PSD Analyzer 



-CSD Analyzer 

 Fig. 1 Magnetic tape-recording system 



r^\. /\y^A^J^ 



Time 



0.0 1 L_ 



Fig. 2 Probability distribution 



in the order listed, and will briefly illustrate the appli- 

 cation of the various types of analyses to aeronautical 

 research. 





Input f Ct) 



Reterence \ 

 Level, Er 



M ) , Sconninq 

 Motor 



Linnited Output i 



nniouwi 



Recorder 

 Fig. 3 Probability distribution analyzer 



0.8 



"o.e 



0.4 



0.2 



— Analyzer Plot 

 o Nlumerica'ty 



Determined 



Points 



-800 -400 400 



Shear Loads, Pounds 



Fig. 4 Distribution of wing shear loads 



J 

 00 



Magnetic Tape Recording and Playback System 



Au essential part of the data processing facility is the 

 magnetic tape recording equipment illustrated in Fig. 1. 

 This ecjuipment provides a means for storing the data 

 in such a way that it can be accurately reproduced in a 

 form most suitable for analog processing. 



Instead of recording data directly on magnetic tape 

 a frequency-modulated carrier system is used. This 

 permits the storage of very low frequency and d-c data 

 and eliminates much of the spurious amplitude varia- 

 tion which would otherwise be caused by tape imper- 

 fections and tape wear. It also makes possible the di- 

 rect recording of FM radio telemeter data. 



Where the data to be processed are produced by a 

 stationary facility such as a wind tunnel, the tape re- 

 corder and FM modulators are located at the facility. 

 Where the data are produced by an airplane, helicopter, 

 or rocket-propelled missile, the data are transmitted to 



a tape recorder on the ground by a radio telemeter link. 

 Or, if the data to be processed have been previously re- 

 corded as a trace deflection on photographic paper or 

 film, a transcribing machine is used to convert film de- 

 flections to a frequency modulated carrier which is re- 

 corded on tape. 



Use of magnetic tape recorders provides a great deal 

 of flexibility in handling data samples. Sample lengths 

 and frequency ranges can be expanded or compressed 

 bj' factors as high as 240 to 1 simply l)y changing the 

 tape speed. Data samples from 1 sec to several min- 

 utes in duration and containing frequencies from dc 

 to 6000 cycles per sec or 7000 cycles per sec can be 

 recorded and reproduced by the FM system. If neces- 

 sary, higher fretiuencies can be handled by eliminating 

 the frequency modulated carrier and recording directly. 



The analog analysis methods require that data sam- 

 ples be scanned a large number of times by the analyz- 



