Page 7 of 12
2.0 Operation of the power amplifier
Meggitt Sensing Systems manufactures a comprehensive line of vibration generating systems,
including electromagnetic and piezoelectric shakers. Electromagnetic shakers are powered
directly from the output of the power amplifier. However, piezoelectric shakers require a matching
network between the power amplifier and the shaker. A signal source to drive the power amplifier
is not part of the system and must be supplied by the user. This guide describes the operation of
the PA8HF power amplifier. Other guides describe the operation of the matching networks and
shakers. For all vibration generating systems a customer supplied signal generator is necessary
to operate the vibration generating system. A piezoelectric accelerometer to monitor vibration
output is strongly recommended.
2.1 Using the power amplifier with an electromagnetic shaker (models F3, F4,
F5B, F10)
2.1.1 Piezo filter switch:
The power amplifier drives electromagnetic shakers directly. The
switch should be set to the “OUT” position.
2.1.2 Output fuse:
The output fuse is used to protect the shakers and matching networks
attached to the output of the amplifier. Users may wish to replace the 12 Amp fuse shipped with
the amplifier with a smaller value to insure excessive current is not applied to the electrodynamic
shakers. Use AGC or 3AG type fuses. The maximum safe current to each shaker is as follows:
Model
Current
F5B
0.1 Amp
F3
0.75 Amp
F4
1.5 Amp (no cooling unit)
2.5 Amp (with cooling unit)
F10
4 Amp
2.2 Using the power amplifier with a piezoelectric shaker (models F7, F7-1,
D60L, D60H, D125L)
The power amplifier will drive piezoelectric shakers, but must have a matching network between
the power amplifier and the shaker. High pass filtering at 500 Hz (-3 dB point) is selected by
setting the piezo filter
switch to the “IN” position.
Note:
The amplifier requires external fan cooling when operated at or near maximum power for
extended periods. The fan aids the dissipation of heat from the heat sink cooling fins. Operating
with no fan may allow the thermal shutdown of the amplifier to engage during testing.
CAUTION:
In these modes of operation power amplifier must be used with a
Wilcoxon matching network. Do not attempt to operate the power amplifier without
the appropriate matching network.
CAUTION:
The impedance matching transformers used in the matching networks
are not designed for use at low frequencies. NEVER attempt to drive the matching