inserts
is
0.16 inches (4.0 mm) long, measured
down
from
the table surface.
The
hole
is
0.27 inches (6.8 mm) deep.
The second
cause
of
abuse
is
the application
of
excessive mounting to-
rque. A
safe
limit
for
the
mounting
torque
of
the
Type
4809
is
30
lb.in.
(0.35
kgm).
To
install
an
insert, the insert
is
placed on the
tool,
with
the pin
of
the
tool
inside
of
the insert internal thread and
with
the blade
of
the
tool
in the
slot
of
the insert. Both the insert and the hole
are
thoroughly
cleaned
with
a
solvent
to
remove all traces
of
oil
or
contaminants
from
fingerprints. A
drop
of
cement
is
placed on the insert external threads,
and
the insert
is
screwed
into
the hole.
If
properly installed, the upper surface
of
the insert should
be
about
0.1
millimeters
or
0.005 inches below the table surface.
If
an
insert
is
damaged,
it
can
be
unscrewed
with
the
same
tool.
It
is
advisable
to
heat the insert
with
a soldering iron
to
weaken the cement
before unscrewing.
2.4.
ADDITIONAL
COOLING
Under normal operation,
up
to
its rated current
of
5 Amperes, the 4809
can
operate continuously
without
overheating. However, since the table
is
an
integral part
of
the
moving element skeleton, its temperature
can
increase
considerably under
full
load conditions.
If
the specimen
is
temperature-
sensitive, this could
have
some effect on the test. For instance,
with
many
accelerometers,
an
increase in temperature
of
10°C
can mean a change in
sensitivity
of
2%.
For
this reason, openings in the casing
of
the Exciter
are
provided
so
that
additional cooling may
be
provided.
If
the
two
steel plugs on either side
of
the
body
are removed, compressed air
fittings
may
be
screwed in. The
openings
are
threaded
with
12 mm threads
with
1.75 mm
pitch.
2.5. POSITIONING THE
EXCITER
For
accelerometer calibration
or
testing
of
small objects up
to
1
kg.
the
Exciter
would
normally
be
used in its
upright
position, standing on the
rubber feet provided.
For
many
uses,
though,
it
is
more convenient
to
take
the Exciter
to
the test object and operate
it
in a position other than the
upright
one.
7
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