BRUEL & KJAER 2203 - Attenuator Controls; Filter and Output Connections

METER LIGHT SWITCH:
METER MECHANICAL ZERO
ADJUSTMENT:
When checking the batteries (METER SWITCH in "Batt." position), the
meter n' eedle deflection must be in the range indicated by the red lines
labelled "Battery" on the lowest meter scale.
The METER SCALE is illuminated when this self-releasing switch is
pressed
down. It only functions when the instrument is switched on.
The screw head just below the METER SCALE is adjusted with the in-
strument turned off to give a meter needle deflection on the "-t:JJ"
mark on the meter scale.
Since the 2203 can measure sound levels that vary over a wide dynamic range (from 26
to 140 dB) but the METER SCALE can only display 20 dB of this range at a time, an at-
tenuator system is necessary to set the range of the instrument so that the sound level
will be within the 20 dB indicated on the METER SCALE. In order to minimize the
chances of an overload, and to give the best possible signal-to-noise ratio, a dual attenu-
ator system consisting of INPUT and OUTPUT ATTENUATORS is used. The correct use
of these switches is described in Chapter 3, Operation.
INPUT ATTENUATOR (black):
OUTPUT ATTENUATOR
(transparent):
ADJ.:
EXTERNAL FILTER IN:
EXTERNAL FILTER OUT:
This 8-position switch controls the gain of the input amplifier in 10 dB
steps, and
also selects the internal reference voltage. The range of ro-
tation of this switch is physically limited to a position from "70" dB to
"Ref." being adjacent to the black spot. Maximum input gain is ob-
tained in the fully clockwise position; and the internal reference vol-
tage is selected in the fully anticlockwise position (provided the trans-
parent OUTPUT ATTENUATOR is also set to its fully clockwise posi-
tion).
This 7-position switch controls the gain of the output amplifier in
1 0 dB steps. The range of rotation of this switch is physically limited
so that the red lines on the knob may only be moved anticlockwise
from the black dot. Maximum output gain is obtained in the fully antic-
lockwise position, while the minimum output gain (red lines by the
black dot) is recommended for use whenever possible.
The total gain setting depends on both INPUT and OUTPUT ATTEN-
UATOR positions; the measuring range corresponding to that gain
setting is always directly indicated between the red lines on the
knob.
This screwdriver-operated potentiometer just to the left of the ATTENU-
ATOR switches is used for calibration the 2203. It is adjustable from
"-2" dB to "+4" dB.
Socket for connection to the input of an external filter (such as Octave
Filter Set Type 1 61 3 or 1 /3 Octave Filter Set Type 1 616). The output
impedance is <50 but should be loaded by at least 500 0. Maximum
output voltage is 1, 6 V peak. Accepts plug JP 0006 or cable AO
0007, etc ..
Socket for connection to the output of an external filter to the 2203.
Input impedance is 146 kO/ I 45 pF. An input voltage of 0,31 6 V RMS
corresponds to a full-scale meter deflection. Accepts plug JP 0006 or
cable AO 0007, etc ..
11