BRUEL & KJAER 2512 - Page 13

rally mounted preamplifier of the
high sensitivity Accelerometer Type
8306 .
A miniature meter on the front
panel indicates whether the internal
battery or external power supply vol-
Triaxial Seat-Accelerometer Type 4322
Accelerometer Type 4322 is
specially designed for detecting vib-
ratory motion in connection with
the measurement of whole-body vi-
bration and is intended to be posi-
tioned under the buttocks of a
seated
person. It contains a triaxial
pickup able to detect vibration in
three mutually perpendicular direc-
tions, that is, vertically (Z-axis) but-
tocks to head, transverse (Y-axis)
right to left side, and (X-axis) back
to chest .
The
transducer consists of a se-
mi-rigid ni trile rubber disc 205 mm
("' 8, 1 ") diameter with a contoured
bulge in its centre housing a triaxial
accelerometer which is in turn
mounted on a stiff 75 mm dia. me-
tal disc . To make the transducer
comfortable to sit on, the rubber
disc is only 3 mm thick at its peri-
phery , increasing to 1 2 mm thick at
its centre and is flexible so that it it
is able to deform to follow the seat
contours .
Transducer dimensions are in ac-
cordance
with the requirements of
SAE Recommended Practice J 1 01 3
(1973) .
Charge Sensitivity:
1 pC / ms-2 , ± 2%
(- 10 pC/ g)
Frequency Range:
Built-in triaxial accelerometer element:
0, 1 Hz to 2 kHz( + 5%)
Complete seat accelerometer on simu-
lated seat: 0, 1 Hz to 100 Hz(+ 5%)
Capacitance:
1 200 pF including 3 m integral cable
Maximum Transverse Sensitivity:
(of each element) < 4%
Piezoelectric Material:
PZ 27
Configuration:
Delta Shear®
Minimum Leakage Resistance:
(at 20°C)
>20GO
Fig.10 . Accelerometer Type 4322 seen
from the underside
Two 1 ,2 m long straps (DH 0411)
are provided which can be threaded
through the 40 mm wide slots in
the transducer to hold it in position
on the seat during rough rides, or
for example, to strap the transducer
to the human chest.
The accelerometer pickup con-
tained in the 4322 has three separ-
ate
Delta Shear® elements assem-
bled in a common housing. They
are of the Uni-Gain® Type which
Specifications 4322
Typical Temperature Transient Sensitivity:
(Measured with Human -Response Vibra-
tion Meter Type 2512 . Worst case with
motion sickness selected)
3
ms-2 /° C
Materials:
Accelerometer Case:
Nickel-plated brass
Base Disc: Nickel-plated brass
Moulded Cushion: Oil resistant nitrile
rubber , hardness - 80 IRHD
Dimensions:
tage is sufficient to power the 251 2
satisfactorily .
means that their sens1t1v1ty has
been
adjusted during manufacture
to be 1 pC/ms-2 ("' 10 pC/g)
within a 2% tolerance. This feature
avoids the necessity of separate
gain adjustment in each channel of
the measuring instrument .
Signal output from the acceler-
ometer is via three miniature coax-
ial sockets
feeding three screened
teflon cables which are grouped
into a common 3 m long output
cable. The output cable is secured
in the pickup by a bush crimped to
the cable, this prevents excess ten-
sion being applied to the three con-
nectors .
A
6-pin DIN screw-locking plug
matching the input of the Human-
Response Vibration Meter Type
251 2 terminates the 3 m long out -
put cable.
The
bottom plate of the transdu-
cer is fastened with six screws and
sealed
with a rubber gasket. In the
event of cable damage it is there-
fore possible to gain access for re-
placement .
Environmental Temperature:
-10 to+ 70°C
(-60 to + 1 50°C for short periods)
Accelerometer alone 200°C
Cable:
Three in one, low-noise , individually
shielded, Teflon insulated
Length: 3 m ( 10 ft)
Connectors: Accelerometer end, three
miniature coaxial plugs
Remote end, 6 pin DIN screw-locking
plug JP 0602
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