carried out and recorded automatically. The measurement procedure using this arrangement
of
instruments is as follows:
1.
Connect the instruments as shown in Figure
4.12.
using the cables stated: ·
2.
On
the rear panel of the
1621,
set the controls as follows:
POWER SELECTOR
MAX. VOLTAGE
"Internal Battery"
"1 V RMS"
3.
On
the front panel
of
the
1621,
set the controls as follows:
SWEEP CONTROL
FILTER
"Auto"
"Linear"
4.
On
the
2306,
ensure that frequency calibrated paper Type
QP
0120,
QP
0124,
QP
0143,
or
QP
0224 is fitted, and that no signal cable is connected. Set the other controls as follows:
RECORDING MODE
WRITING SPEED/LF LIMIT
SENSITIVITY
PAPER DRIVE
PEN
DRIVE
POWER
"DC
Lin"
"250
mm/s
I
25
Hz"
"O"
"On"
"On"
"On"
Adjust the
DC
LIN
POSITION control to place the pen on the bottom line
of
the paper, as in
Fig. 4.13. and reconnect the signal cable, ensuring that the switch at the side is in the
"+"
position.
5.
On
the
2512,
set the FILTER SELECTOR on the rear panel to the "Weighting Filter in, Ext.
Filter
in"
position, the INPUT SELECTOR to "Ref.", select any measurement mode except
the
"O,
1 - 0,63
Hz
MOTION SICKNESS" mode, and press the
ST
ART push-key. This
gives a reference signal equivalent to
120
dB
(1
ms-
2
)
in the WHOLE BODY mode or
140
dB
(10
ms-
2
)
in the HAND-ARM mode.
6.
Using only the SENSITIVITY control on the 2306, adjust the pen position to lie on the third
line from the bottom
of
the paper, as shown in Fig.4.13. This line should be labelled
120
dB
or
140
dB as appropriate. The system is now calibrated.
DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDODODODDDDDDDOOODDDDD
Bruel & Kja,r
dB
dB
150
170_
Internal Reference Level
from
2512
140
10ms
2 160
100ms
2
120 dB
(1
ms-
2
)
for
Whole Body
130
150====
140dB
(10
ms-2)
for
Hand-Arm
.
140 1
ms
2
140
10ms
2
Lower
Limit
of
Measurement
.
100dB
(0,1
ms
2
)
for
Whole Body
110
130====
120dB
(1,0ms
2
)
for
Hand-Arm
:
.
100
0,1
ms
2
120
1 ms
2
OP
0102
WB
H· A
810428
Fig.
4.13.
Calibrating the Level Recorder
7.
Adjust the paper position on the 2306 until the pen lies at a value beginning with 2 on the
frequency axis, and set the FILTER and FREQUENCY RANGE controls on the
1621
as
required.
41
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