Reference
Acce
lerometer
6.
Upper ra
dial flexure
Magnetic
Shield
_..,~-
Moun ting
holes for
pro
tecti
ve
ca
n
Fram
e
Moving element
ske
let
on·
rib
edge
Fl
ex
ur
e
mounti ng block
Lower radi al fle xure
Tangent ial
flexure
Split
hub
~~~
_
_ _ _
_-
_ _
Driver
Coil
' - - - - - - - 1 . - - - - - - - " " " ' / - - - - - - - - - -
Drive connector
t
o
amplifier
272
(0
1
Fig. 6. 10. Calibration Head 4815
6.
3.1
. Reference Accelerometer
The accelerometer built into the Type 4815 Head is a Standard Accelerometer Type
8305. It has been designed particularly for the precise ca libration of transducers by the
back-to-back comparison method. Careful design resulted in very low transverse and base
strain sensitivities, assuring a high degree of
accuracy
in comparison measurements
.
Long term stabil
ity
and low sensitivity to temperature changes are obtained by using a
piezoelectric element of quartz. A sectional drawing of the accelerometer is shown in
Fig.6.11
.
Construction is of the inverted single
ended
compression type, and a full dis
cussion of its characteristics is contained in the "'Accelerometers"' Instruction Manual.
Fig.
6.
11. Cross-sectional view of the Type 8305 A
ccelerometer
On a 4815, as delivered from the factory, the accelerometer
is
already
mounted.
How
ever, in case it should be necessary at ariy time to remove the accelerometer from the
4815 Head, the following mounting instructions are included.
40