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which measures the average value of the output voltage. It is calibrated in
RMS values for sinusoidal voltages.
The sensitivity of the voltmeter is automatically changed when the position
of the switch marked MATCHING IMPEDANCE is altered. Full deflection of
the meter is indicated on the switch. In addition to the volt calibration on the
switch ATTENUATOR OUTPUT there is also a dB calibration ,and the cali-
bration is, as mentioned above, given in dB re. 1 volt. An example will ex-
plain the use of the dB scale: If the OUTPUT LEVEL is adjusted in such a
way, that 20 dB is read on the meter scale, and the switch ATTENUATOR
OUTPUT is in the position
-
30 dB then the signal level at the output socket
will be 20-30
=
-10 dB re. 1 volt (o.316 V).
When the MATCHING IMPEDANCE switch is in position "Att." the output
voltage available from the ATTENUATOR OUTPUT will depend on the
position of the ATTENUATOR OUTPUT switch, in this case full deflection
of the meter corresponds to the value indicated by the switch position.
The signal-to-noise ratio of the Oscillator is greater than 70 dB for maximum
output voltage. By "noise" is here meant: The root mean square of internally
induced noise, hum and spurious frequencies
.
1.5
%
7
~-
I
I
v
/
LOAD:
2.5wotts
/
_,-"
I
f .
0.7
g
0.5
~
(II
:0
g
0.3
~~
~)<
vi-
1
LOAD
:
1 watt
~
~
......
""
.....
,
~
~---
- - -
1-- -
~
-::/
~
'
'
,
•
~
J
\
I
" -,
/""
/
'
,/
~~"
_,/"
/
"r-...
\
_.,....
c
::r
0.2
\
1
v..
ATTEN
1
~~~~~ OUT~UT
5
z
L
0.15
0.1
0.
1
0.2
0.5
1
10
20 kHz 50
100
200
500
~
Frequency
f62.?62
Fig. 1.3. Distortion curves for different loads. The curve marked »Att. 5 Volts"
is obtained from measurements taken on the ATTENU ATOR OUTPUT terminal,
open circuited.
·
Power Supply.
The Oscillator can be operated from a 240, 220, 150, 127, 115 or 100 volts AC,
50--400 Hz power line, the power consumption being about 70 watts.
The proper voltage is selectable by a switch-fuse combination situated at the
rear of the instrument. To select the voltage it is necessary to remove the
fuse by turning the hexagonal disc head in the centre of the switch anticlock·
9
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