2
The type and size of the required impact device is determined by the test structure. The
Model 088A Modal Punch was designed for use on intermediate size structures such as
automotive axles, gearbox shafts, and machine tools. Large, heavy structures such as
locomotive frames, tanks, and bridges require an instrumented sledge hammer (PCB
®
model numbers 086D20 or 086D50). Small structures such as compressor blades or
some electrical circuit boards often require a miniature instrumented hammer (PCB
®
model number 086D80). Some very large structures may require a special mechanical
ram instrumented with a force-sensing impact head.
The Modal Punch is instrumented with a precision, quartz, ICP
®
(low impedance) voltage
mode force sensor. The built-in conditioning electronics allow ease of use and test set-
up, while the naturally-polarized quartz sensing element offers long-term stability and
repeatability.
2.0 Description
The Modal Punch consists of an integral ICP
®
(Integrated Circuit Piezoelectric), quartz
force sensor mounted on the impact head. The sensing element and built-in, solid state
micro-electronics inside the force sensor function to transfer impact force into a low
impedance analog signal for display and analysis. The cable is connected on the side of
the Modal Punch
’
s Connector Adaptor model number 070A41 (supplied) just below the
impact surface. An Extension Shaft model 084A80 is also supplied to adjust the Modal
Punch to the desired length. Additional shafts may also be purchased. A foam grip is
supplied to provide a comfortable and secure grip and may be replaced when needed.
The striking end of the Modal Punch
’
s head has a threaded hole to accept a variety of
impact tips. The tip functions to transfer the force of the impact into the sensor and
protects the sensor face from damage. Tips of different stiffness allow the user to vary
the pulse width and frequency content of the force.
All component parts (impact head, extender, and connector adaptor) are laser-welded and
epoxied at the factory to ensure reliable operation in adverse environmental conditions.
3.0 Installation
To assemble the Modal Punch, choose the number of extenders required to reach the
desired impact location, screw the extender onto the force-instrumented impact head, and
attach the connector adaptor to the extender or the force-instrumented impact head, if an
extender is not being utilized. To ensure a proper mechanical coupling between the parts
of the Modal Punch, each piece should be securely screwed together. Care should be
used not to over-torque the parts, which will cause permanent damage to the interface and
connectors. A firm, hand-tight torque is sufficient to ensure a proper coupling. If
desired, a small amount of silicone grease (DC-4 or equivalent) may be applied between
the interfacing parts for an improved coupling.
Summary of Contents for 088A
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