Technical Description - BRUEL & KJAER 1022 Instructions And Applications

3. TECHNICAL DESCRIPTION
A block diagram of the 1022 is shown in Fig.3.1.
Eat .
120kHz
Mod. Output
Input
Fig.3.1.
Remote
Control
Input
Block Diagram
Lood
Output
Attenuotor
Output
The fixed oscillator is a tuned LC type and works at 120 kHz. I ncorporat-
ed in the tuned circuit is a variable capacitor which is operated by the
Frequency Increment knob. This allows exact frequency selection within
±50 Hz about any setting on the main scale. In addition this capacitor per-
mits frequencies down to 10 Hz to be obtained at the risk of slightly more
distortion.
An output to supply a reference signal or a control signal for the Hetero-
dyne Slave Filter 2020 is provided. The output impedance of the 120 kHz
output socket is lOOn and the signal level is of the order of 200 mV.
The fixed oscillator can be frequency modulated to produce a warble
tone. The oscillator is connected directly to a reactance circuit to enable
external modulation of the signal, but in the case of internal modulation a
relaxation type of oscillator employing a unijunction transistor to control
the reactance circuit is also used.
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