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Turn the freq1:1ency scale pointer of the Oscillator to 20 Hz, that is to a
position corresponding to the position of the recorder stylus on the pre-
calibrated recording paper, and set AUTOMATIC SCANNING switch to "On".
Now the recording can be started by pressing down the SINGLE CHART-
CONT. RECORD. pushbutton for a short while and then release it, and the
frequency characteristic will he recorded automatically on the paper strip.
Normally earphones are measured under the conditions described above
which are constant voltage conditions. However, by connecting a resistor
in series with the earphone and using the voltage drop across this resistor
to control the compressor circuit of the 1022 constant current conditions can
be obtained for the test.
Artificial Ear in Connection with the Precision Sound Level Meter.
As amplifier and indicating meter
it
is possible to use the Precision Sound
Level Meter Type 2203. The Artificial Ear and 2203 make a very handy
combination for audiometer control, and the measuring set up must be
adjusted in the following way: Assemble the artificial ear as described under
"Operation
of the Artificial Ear" page 10 and use the coupler suited for the
earphone. Feed the signal to the earphone, for example from an audiometer
Fig. 2.3, or another generator. Connect the Artificial Ear to the Sound Level
0
0
6
oo
6
·o o o
o
udiometer
2203
4152
-16375'2
Fig. 2.3. Measuring set-up used for audiometer control.
Meter.
See Fig. 2.4. Remove one of the rubberfeet from the Artificial Ear
and screw it under the Sound Level Meter (see Fig. 1.3b). Adjust the Sound
Level Meter as follows (Fig. 2.5):
1. Pull out knob 1 and turn it to position "Batt".
The meter pointer should now deflect to within the red area marked
BATTERY indicating that the batteries are alive. If it does not, replace
the batteries.
2. Turn knob 1 to "Lin".
3. Turn knob 2 fully anticlockwise.
14
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