REFERENCES 



used to apply force to a preparation, does it matter if the force changes as 

 the preparation moves? Impedance considerations will narrow the field 

 of choice considerably. 



The frequency response of the transducer must now be matched to the 

 experiment. Must the transducer respond to steady deflections? What is 

 the highest frequency present in the signals under study? Whether the 

 transducer is to be static or dynamic, and how high its resonant frequency 

 must be, can now be decided. 



The design of the transducer will now be fairly clear, and it may be either 

 obtained or constructed. It is then essential that it should be tested under 

 the experimental conditions. Generally it is simpler to determine the 

 transient response than the frequency response; a sudden electrical signal 

 can be applied to an electromechanical transducer, while a suitable mechani- 

 cal shock to a mechanoelectrical transducer can usually be arranged. An 

 estimate of the resonant frequency and damping follows from experiments 

 of this type. It is now possible to confirm that the properties of the trans- 

 ducer will not unduly modify or distort the signals. 



Tests of sensitivity and freedom from external influences are straight- 

 forward. Electrical or magnetic screening and possibly isolation from 

 mechanical vibrations may be necessary. 



Finally it may fairly be said that if the properties of the transducer and 

 the extent to which it distorts the experimental results are not understood, 

 it would be better to do the experiment another way. 



REFERENCES 



1 Canaway, R. J. et al. Electron. Engng. 11 (1955) 103 



2 Farrar, J. T., ZwoRYKiN, V. K. and Bawn, J. Science 126 (1957) 975 



^ King, R. W. P., Mimno, H. R. and Wing, A. H. Transmission Lines, Antennas 



and Wave Guides McGraw-Hill. 1945 

 ^ Terman, F. E. Radio Engineering, p. 75. McGraw-Hill. 1951 

 ^ Radio Corporation of America. Data Sheet Type 5734 Mechanoelectronic 



Transducer 

 « Pascoe, J. E. /. Physiol. 128 (1955) 26P 

 ' Lauer, H., Lesnick, R. and Matson, L, E. Servomechanism Fundamentals 



McGraw-Hill. 1947 

 ® West, J. C. Servomechanisms E.U.P. 1953 

 ^ Porter, A. Introduction to Servomechanisms Methuen. 1950 

 ^" Muirhead Ltd. Catalogue 



11 Williams, F. C. and Uttley, A. M. /. Instn. elec. Engrs. 93 Pt. Ilia (1946) 1268 



12 Owen, D. Alternating Current Measurements Methuen. 1937 



13 Johnstone, G. G. Wireless World 63 (1957) 8, 70, 124, 275, 378 



1* Sturley, K. R. Radio Receiver Design, p. 294. Chapman & Hall. 1947 

 15 ScROGGiE, M. G. Wireless World 62 (1956) 158 

 1" Johnson, L. W. Wireless World 63 (1957) 23 



17 Williams, F. C. and Uttley, A. M. /. Instn. elec. Engrs. 93 Pt. Illa (1946) 

 1256-1274 



18 Hansen, A. T. Acta physiol. scand. 19 (1950) 306 

 1^ Hansen, A. T. Acta physiol. scand. 19 (1950) 333 



2** Hansen, A. T. Pressure Measurements in the Human Organism Copenhagen 



Teknisk Forlag. 1949 

 21 Machin, K. E. To be published. 



509 



