Inserting the battery with its polarities reversed will doubtless
result in the destruction of the measuring instrument.
6. Battery test
Set the On/Off rotary switch (3) to the "Batt" position. For a
good battery, the pointer deflection must reach into the red
"Batt-Test" area of the analogue indicator (5). If this is not the
case, the battery must be replaced as described under point 5,
otherwise perfect operation of the measuring instrument is no
longer guaranteed.
7. Performing measurements
7.1 Filter selection switch
The weighting filter is selected using the filter selection switch
(4). In switch position "A" the frequency response of the Sound
Level Meter matches the characteristics of the human ear, conse-
quently environmental noise (vehicles, machines etc.) is general-
ly measured in dB(A) units.
Switch position "C" is normally reserved for measurements of
acoustic sound signals and sound emitted by bodies (loud-
speakers, etc.).
The frequency response of the filter can be obtained from the
following illustration.
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Sound in dB
+10
0
- 10
- 20
- 30
- 40
- 50
20
7.2 Damping selection switch
The damping of the pointer deflection can be set to one of two
settings using the "Response" selection switch (2).
If the sound source to be measured is transmitting sound waves
only briefly, or if the maximum volume is to be measured, set the
damping selection switch (2) to "FAST".
If the mean volume of a sound source is to be measured, set the
selection switch (2) to "SLOW".
7.3 Attenuation selection switch
At the start of every measurement, set the attenuation selection
switch (3) to the highest attenuation value "120" and reduce the
attenuation value until a pointer deflection results.
The dB value of the sound source being measured is derived as
follows:
DB (C) Filter
DB (A) Filter
DB (C) Filter
Randon Inciderce refpouse
=
0°
free field refpuse characteris tic at 0 Degrees
=
90°
grazins incipence refpouse (90 Degrees)
=
20
100
200
500
1k
Frequency in Hz
2
5
10
20
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