644 
II, BASIC ELECTRONTC EQUIPMENT 
1. Amplifiers 
The requirements of an amplifier for recording transient signals de- 
pend, of course, on the nature of the transient: its magnitude, the im- 
pedance of the gauge or pickup circuit, the maximum rate of change, and the 
duration of the signal, For example, shock pressures or accelerations rise 
very rapidly to a large peak value and fall to a very small value in a few 
milliseconds, whereas displacements or bubble=pulse pressures may have only 
a gradual smooth rise over a comparatively long time interval. In the first 
case, severe demands are imposed on the high-frequency response; in the sec- 
ond, the response must be good at long times after application of a signal 
if distortion is notte result. An amplifier to be used with a piezoelectric 
gauge or other high-impedance device must have a high input impedance ih 
order not to distort the signal, and under some sonditions it is essential 
that it not be microphonic as a result of shock. No matter what its use, 
the amplifier should have sufficient undistorted output to provide an adequate 
range of deflection voltage for the cathode-ray tube plates, and its gain 
should remain constant over a period of time sufficient for recording and 
calibration. 
(a) Frequency-response characteristics, -- The frequency-response re- 
quirements for recording transients can best be appreeiated by considering 
specific cases, An arlalysis which has proved useful in work at UERL is that 
of the effect of simplified response functions, which approximate the charac- 
teristics of resistance-coupled amplifiers, on a transient pulse having the 
form of a discontinuous rise followed by an exponential decay, The rocanite! 
are sufficiently simple to bring out clearly the design problems and proper- 
ties of circuit transient response and to give an approximate idea of the 
errors to be expected in practical cases. 
1 These results have been reported elsewhere in less detail; see Meas- 
urement of underwater explosion pressures, by E. B, Wilson and R, H. Cole, 
e) 230 
