polarized discs of piezoelectric ceramic backed 
with potting compound and operating in the 
thickness-resonant mode at about 3 megacycles 
per second. The electronic circuitry has only 
five transistors (all type 2N393) and requires 
a 13-volt power supply from which it draws less 
than 5 milliamps. A regulated power supply 
employing a rechargeable battery, which can be 
submerged with the velocimeter, has also been 
developed at LMSC. 
NOMENCLATURE 
C = speed of sound, meters per second 
f = pulse repetition frequency, pulses per 
second 
L = path length, meters 
t = time delay in electronic circuitry and 
transducers, seconds 
T = transit time in liquid, seconds 
REFERENCES 
1. 
26 
36 
he 
Thomas D. McGrath, Capt., USN - UNDERWATER 
ENGINEERING, 1, 3, pe 38 (1960). 
V. M. Albers, UNDERWATER ACOUSTICS HANDBOOK 
(The Pennsylvania State University Press, 
University Park, Pennsylvania, 1960). 
K. V. Mackenzie, J. ACOUST. SOC. AM. 32, 
100 (1960). = 
Wayne D. Wilson, J. ACOUST. SOC. AM. 32, 
641-644 (1960). = 
F, E. Bellas, J. ACOUST. SOC. AM. 33, 2h9 
(1961). i 
M. Greenspan and C. E. Tschiegg, RuV. scl. 
INST. 28, 11, 897-901 (1957). 
C. #. Tschiegg and E. E. Hays, J. ACOUST. 
SOC. Ali. 31, 7, 1038-1039 (1959). 
M. Greenspan and C. E. Tschiegg, J. Ri- 
SEARCH OF NATIONAL BUREAU OF STANDARDS 59, 
4, 29-254 (1957). a 
FIG.3 
189 
