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4.1.2. Driver Amplifier
This is a simple two stage, transistorized push-pull power amplifier
which provides an impedance match between the output of the oscillator
and driver coil of the vibration system. The amplitude of the output signal
from the Driver Amplifier determines the peak acceleration level of the
vibration table and may be adjusted using the AMPLITUDE potentiometer
control to regulate the input signal to the amplifier.
4.1.3.
Vibration'
System
A schematic diagram of the vibration system is shown in Fig.4.2. Its
principle of operation is extremely simple. The vibration table is excited by
a sinusoidal force produced by an electromagnet operated from the 79.6 Hz
voltage from the output of the Driver Amplifier.
Shaker table
10-32 NF threaded hole
Resonance
adjustment
27f23(
Fig.4.2. Schematic diagram of the vibration system of the 4292
The vibration table has a
10-
32 N F hole for mounting accelerometers
and is supported by a taut bronze band. To correct for different accelerome-
ter masses which may be placed on the vibration table, the mechanical
resonance of the table may be adjusted to 79.6 Hz by altering the tension of
the bronze band using the RESONANCE control at the rear of the instru-
ment. The acceleration level at which the table vibrates may be adjusted
using the AMPLITUDE control to regulate the i'nput to the Driver Ampli-
fier. To facilitate calibration of the table's acceleration level, a small bronze
15
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