SOURCE 



SHUTTER 



DETECTOR 



APERTURE 



Fig. 11. Analog-to-digital converter. 



A pressure transducer configured for under- 

 water use is diagrammed in Fig. 12. The pressure- 

 tight compartment with "0" ring seals contains 

 the helical bourdon tube which operates the 

 shutter. With this type of bourdon tube there 

 are no extra mechanical linkages ; one end of the 

 helix is attached to the pressure port and the 

 other end to the rotary shutter. 



A corresponding configuration for a tempera- 

 ture transducer, utilizing a bimetallic ther- 

 mometer movement to operate the rotary shutter 

 is shown in Fig. 13 . A good bimetallic movement 

 is capable of a 3-second time constant. A some- 

 what shorter time constant may be obtained by 

 using a temperature sensor of the type employed 

 in an ordinary mechanical bathythermograph. The 

 latter sensor consists of a long thin tube full 

 of toluene that expands with rising temperature 

 and operates a bourdon tube. 



The remaining figures show a proposed appli- 

 cation of nuclear digital transducers in a 

 digital bathythermograph. Fig. ik shows a block 

 diagram of the underwater unit which contains 

 a coupling unit to permit multiplexing the sig- 

 nals. The single conductor performs 3 functions; 

 it carries power down to the underwater elec- 

 tronics, pressure and temperature signals up 

 from the transducers and DC control pulses down 

 to the underwater unit for in situ calibration. 



For checking the transducer calibration, a 

 DC control pulse gates a generator which 

 operates an electric switching device in the 

 underwater unit, thus simulating zero and full 

 scale transducer readings. Such simulated 

 readings can be obtained in either of two ways : 

 (a) by use of an auxiliary source and detector 

 in fixed geometrical relationship or (b) by 

 rotating the shutter so as to fully open or 

 fully close the aperture. An underwater unit, 

 containing these components in a housing similar 

 to the standard electronic bathythermograph 



legend: 



a= source capsule 

 b = particle detector 

 c= shutter 

 d= helical bourdon tube 



E = 0PENIN5 TO SEA PRESSURE 

 F= ELECTRONIC COMPARTMENT 

 G,H=0-RING SEALS 

 1= WATERTIGHT CABLE CONNECTOR 



Fig. 12. Pressure transducer. 



legend: 



a = source capsule 

 b= particle detector 

 c= shutter 



d= bimetallic thermometer 

 movement 



E= PRESSURE TUBING Vg O.D. 

 F= ELECTRONIC COMPARTMENT 

 G,H=0-RING 

 1= WATERTIGHT CABLE 

 CONNECTOR 



Fig. 13. Temperature transducer. 



specified by the U. S. Navy Oceanographic Office, 

 is illustrated in Fig. 15 . 



A block diagram of the deck unit is illustrated 

 in Fig. 16. The digital equipment includes two 

 counters with variable and programmable time bases 

 to give readouts directly in temperature and depth 

 units, and a digital printer or other recording 

 device. The analog equipment includes two simple 

 integrating circuits and an X-Y recorder. The 

 test control panel shown at the top of Fig. 16 

 is used to actuate the in situ calibration system 

 described above. The deck unit would be equipped 

 with records for making both analog, and digital 

 records. 



Although the above discussion has been limited 

 to the application of nuclear digital transducers 

 in a bathythermograph, these devices are also 

 being evaluated for other applications . Inasmuch 

 as the cost of the sensing heads is expected to 

 be moderate for pulse rate transducers of excel- 

 lent long term stability and high accuracy, 

 their suitability may depend upon system require- 

 ments as to sampling rate or data rate. It is 

 apparent that increased readout accuracy can be 

 obtained at the expense of sampling rate and vice 

 versa. 



179 



