16 I— 



10 20 30 40 50 60 70 80 90 100 

 SHUTTER OPENING ( I0" 3 INCH) 



Fig. 9- Transducer readout graph - sliding 

 shutter. 



taken with the door being opened only briefly 

 in order to change the micrometer settings. 

 This plot was completely indistinguishable from 

 Fig. 9 showing that a temperature change of this 

 magnitude had a negligible effect . 



ACCURACY 



In considering the accuracy of nuclear digital 

 transducers it is necessary to distinguish the 

 mechanical sensing accuracy from the purely 

 statistical readout accuracy. Stated differently 

 the readout of shutter position can be obtained 

 to any desired statistical accuracy simply by 

 accumulating a sufficient number of counts. 

 This means that a nuclear digital transducer is 

 an infinite resolution device. 



The mechanical sensing accuracy of the trans- 

 ducer is limited entirely by the mechanical 

 sensor. For example, although bourdon tubes of 

 good linearity and low hysteresis are available, 

 these sensors still have certain deficiencies 

 which should be capable of measurement by means 

 of a nuclear digital transducer. These trans- 

 ducers, due to their infinite resolution and low 

 friction, may offer an improved means for 



5 10 15 20 



SHUTTER ROTATION ( DEGREES) 



Fig. 10. Transducer readout graph - rotary 

 shutter. 



measuring the performance limitations associated 

 with various types of mechanical sensors. 



If the transducer is to measure a changing 

 variable, the accumulated count will represent 

 an average over the time interval determined by 

 the time base generator. This automatic averaging 

 feature may be desirable in certain applications 

 for the purpose of eliminating the effect of 

 rapid signal fluctuations. 



APPLICATIONS 



In discussing applications of nuclear digital 

 transducers, we shall first mention the obvious 

 one consisting of an analog-to-pulse rate or an 

 analog-to-digital converter based on a D'Arsonval 

 meter movement. Such a device is illustrated in 

 Fig. 11, in which the detector, shutter and 

 aperture are visible. The shutter is attached to 

 the moving coil of the meter movement. This type 

 of converter might be advantageous for use when 

 digitizing equipment having long term stability 

 and accuracy is required as, for example, in an 

 untended remote data station. 



178 



