3
A precision-machined mounting surface with a minimum
finish of 32
in (0.0008 mm) is recommended. (If, and
only if, it is not possible to properly prepare the test
structure mounting surface, consider adhesive mounting as
a possible alternative). Inspect the area, checking that
there are no burrs or other foreign particles interfering
with the contact surface.
STEP 2:
Wipe clean the mounting surface and spread on
a light film of grease, oil, or similar coupling fluid prior to
installation.
Figure 4.
Mounting Surface Lubrication
Adding
a
coupling
fluid
improves
vibration
transmissibility by filling small voids in the mounting
surface and increasing the mounting stiffness. For semi-
permanent mounting, substitute epoxy or another type of
adhesive.
STEP 3:
Attach supplied washers, insert screws through
hole in accelerometer case, and torque to specified value
per
Installation Drawing.
NOTE:
It is important to use a torque wrench during this
step. Under torquing the sensor may not adequately
couple the device; over torquing may result in screw
failure.
4.2 ADHESIVE MOUNT
Adhesives like hot glue and wax perform well for
temporary installations whereas two-part epoxies and
quick-bonding gels (super glue) provide a more
permanent installation. PCB recommends mounting DC
accelerometers via an adhesive mounting base. The base
acts as a sacrificial part allowing safe removal of
accelerometer after test is completed.
NOTE: Adhesively mounted sensors often exhibit a
reduction in high-frequency range. Generally, smooth
surfaces and stiff adhesives provide the best high
frequency response.
METHOD 1 - Adhesive Mounting Base
This method involves attaching a base to the test structure,
then securing the sensor to the base. This allows for easy
removal of the accelerometer. Contact the PCB factory
representative for optional mounting plate details.
STEP 1:
Prepare a smooth, flat mounting surface. A
minimum surface finish of 32
in (0.0008 mm) generally
works best.
STEP 2:
Attach mounting screws of the sensor to the flat
side of the appropriate adhesive mounting base according
to the guidelines set forth in
STEPS 2
and
3
of the Screw
Mount Procedure presented above.
Figure 5.
Mounting Base: Adhesive Installation
STEP 3:
Place a small portion of adhesive on the
underside of the mounting base/block. Firmly press down
on the assembly to displace any extra adhesive remaining
under the base.
When the accelerometer/base/block assembly is to be
removed, unscrew the accelerometer from its’ mounting
base / block, prior to removal of base/block from test
article.
METHOD 2 - Direct Adhesive Mount
Caution:
It is recommended to use a mounting base
with high sensitivity DC accelerometers
(Method 1),
if at
all possible! Method 2 should be avoided, as a general
rule, to avoid damage to the accelerometer during
removal.
STEP 1:
Prepare a smooth, flat mounting surface. A
minimum surface finish of 32
in (0.0008 mm) generally
works best.
STEP 2:
Place a small portion of adhesive on the
underside of the sensor. Firmly press down on the top of
the assembly to displace any adhesive. Be aware that
excessive amounts of adhesive can make sensor removal
difficult. Also, adhesive that may invade the mounting
holes in the sensor will compromise future ability to screw
mount the unit.
