coil itself
is
wound about a moving element and this
has
a certain
mass.
Hence the acceleration due
to
an
applied force F
will
be:
_ (m
+me)
- F
a
where m
is
the
mass
of
the test object and
me
is
the moving element
mass.
If
the acceleration
is
given in gravitational units
(g)
and the weights
of
the moving element and test object
are
known,
the
maximum acceleration
possible
can
be
quickly
computed. The
maximum
force available
from
the
Type
4809
is
10 lbf. (44.5 Newton). The moving element weight
is
0.132 lb.
(60
gm.).
If
the test object weights 0.37 lb. (.170 kg),
the
maximum
accele-
ration
with
this load
is:
a
2.2. DESCRIPTION
W+We
F
0.13 + 0.37 =
20
10 g
Fig.2.2 shows a
sectional drawing
of
the
Type
4809. The magnetic field,
8, mentioned in section 2.1,
is
here supplied
by
a permanent magnet which
projects
up
into
the
space
enclosed by the driver coil. A cast
iron
magnetic
structure surrounds the magnet in order
to
co-nfine the magnetic force
to
the exciter
as
much
as
possible.
Threaded Insert - -
----,
Tangential
Flexure
Magnetic
Structure
Table
.-
-
---H
HN--
- Permanent
Magnet
Fig.2.2. Sectional drawing
of
a Vibration
Exciter
Type
4809
5
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