108 INSTRUMENTATION IN SCIENTIFIC RESEARCH [Chap. 1 



1-55. Pressure Transducers Based upon Electric Gas 

 Discharges 



The most frequently reported electric gas discharge form for air- 

 pressure and flow-velocity measurements is the corona discharge. 

 The method is described by Werner 1 and Werner and Geronime. 2 

 The system is illustrated schematically in Fig. (1-5)5 and consists of 

 a fine needle point electrode A (Wollaston wire) and a large electrode 



B which may either surround the 

 electrode A or may be a flat or a 

 cylindrical electrode located in front 

 of the needle point and separated by 

 several millimeters from the point. 

 If a voltage E of the order of 1,000 

 to 5,000 volts is applied, a corona dis- 

 charge will form in the vicinity of 

 the needle point, and a current I up 

 to ten or more microamperes will be 

 observed. The general form of the 

 voltage-current characteristics for 

 positive and negative points is shown 

 in Fig. (1-5)6. 



/>' 



Fig. (1-5)5. Pressure transducer 

 based upon electric gas discharges; 

 schematic diagram of point-to-plane 

 and concentric electrode configura- 

 tions. 



25 



20 



s" 



10 



,000 



2,000 



3,000 

 F. volts 



4,000 



5,000 



Fig. (1-5)6. Corona discharge characteristics. Curves A and B for 

 point-to-plane corona, 3 mm spacing, at different pressures; curve C 

 (other geometry), at different velocities [from F. D. Werner, Rev. Sci. 

 Instr., 26, 61 (1950); by permission]. 



1 F. D. Werner, Rev. Sci. Instr., 21, 61 (1950). 



2 F. D. Werner and R. L. Geronime, Tech. Rept. 53-142, Wright Air Develop- 

 ment Center, Wright-Patterson Air Force Base, Ohio, 1953. 



