f.-h 



ACCUMULATOR 



BINARY OUTPUT 



Fig. 10. Block diagram of measuring system. 



The test results demonstrate that a tunnel 

 diode transducer will provide an accuracy of 

 to. 5$ of full scale with high sensitivity. The 

 applicable pressure range extends from atmos- 

 pheric to 20,000 psi. It is our opinion that 

 oceanographers can make excellent use of this 

 device in their instrument systems . 



DISCUSSION AND CONCLUSIONS 



A transducer system for obtaining a direct 

 digital output proportional to pressure has been 

 described. The highly responsive tunnel diode 

 as the pressure transducer provides steady state 

 and transient pressure readings in digital form 

 with a sensitivity of 3 cps/psi when f Q equals 

 300 Kcps and 10 cps/psi when f Q equals 1 Mcps . 

 The demonstrated accuracy is +0.5$ of full scale 

 which we believe is satisfactory for many oceano- 

 graphic requirements. Improvements in accuracy 

 can be foreseen in the near future. 



The ability of the hybrid configuration to 

 operate stably over a wide range of frequencies 

 and provide means for selective direct compensa- 

 tion for nonlinearities make this configuration 

 most attractive. Common mode rejection will 

 reduce the effects of temperature, supply vol- 

 tage changes, etc. 



Reliability, life and performance tests under 

 actual field conditions remain to be conducted 

 but because of its favorable size and digital 

 output the tunnel diode pressure transducer may 

 become an important component of computer oriented 

 oceanographic research instrumentation systems. 



gj absolute value of the negative conductance. 



r resistor. 



C capacitor . 



L inductor . 



Ey., applied voltage 



V voltage applied to transistor in hybrid 

 configuration. 



t time 



f Q frequency at atmospheric pressure. 



f l frequency shift from f Q to f-|_. 



R T total equivalent circuit resistance. 



e c voltage across capacitor. 



k ratio of current to capacitance. 



REFERENCES 



1. ESAKI, L., New phenomenon in narrow ger- 

 manium P-N junctions, Phys . Review, 109 (2). 

 603-601)-, 1958. 



2. MASON, W. P., Semiconductor devices as pres- 

 sure transducers, Electronics , 35(8), 35, 

 1962. — 



3. SIK0RSKI, M E. and P. ANDREATCH, Tunnel 

 diode hydrostatic pressure transducer, 

 Review of Scientific Instruments , 33(2), 155, 

 1962. ~~ 



h. MITCHELL, F. H. Jr., Deriving the tunnel 

 diode curve, Electronic Industries , 20(10), 

 96, 1961. 



5. L0WRY, H. R., J. GI0RGIS and E. GOTTLIEB, 

 Tunnel Diode Manual , General Electric Co., 

 First Edition, I96I. 



LIST OF SYMBOLS 



I_ peak tunnel diode current . 



I v valley tunnel diode current. 



Vp tunnel diode voltage corresponding to the 

 peak current . 



V v tunnel diode voltage corresponding to the 

 valley current. 



19^ 



