Shock Accelerometer
Page 12
002-096e-01.19
Figure 6:
Simplified Diagram of the Shock Accelerometer
The source resistor (Rs), while located in the coupler, is a part of the
source follower circuit. In order for the Piezotron to provide enough
gain, Rs must have a high dynamic resistance while being able to
provide enough current (low DC resistance) as not to affect the high
frequency response of the system. Replacing Rs with a constant
current diode (Figure 7) provides a device with a high dynamic
resistance while allowing sufficient current to flow.
Figure 7:
Schematic Diagram Of A Simple Coupler
Figure 7 shows a schematic of a simple power supply coupler for
shock accelerometers. DC power is supplied from a 24 volt source
such as a regulated power supply or batteries. One advantage of the
Piezotron system is the fact that a simple two wire coaxial cable is
used for both power and signal. Because the signal and power both
share the same line, it is necessary to include the capacitor C to
decouple (or block) the DC from the measurement instrument input.
Operating within the voltage range of 20...30 VDC assures a full
undistorted ±5 Volt output amplitude (See Figure 8). If the source
voltage is reduced, distortion and clipping of the signal will occur if
one attempts to use the full amplitude range of the accelerometer
Quartz
Element
+
PIEZOTRON AMPLIFIER
To Coupler
C
r
R
t
Electrometer Amplifier
Sensor
