Automatic Regulation Of Output Power - BRUEL & KJAER 1022 Instructions And Applications

4. Proceed from point B. 2 or C. 2 as required.
E. AUTOMATIC REGULATION OF OUTPUT POWER
By means of the compressor circuit it is possible to regulate the output
from the oscillator. When a constant voltage is required, the output voltage
from the oscillator should be used as a control voltage. (Fig.4.1 a.). A con-
stant current is obtainable if the voltage drop across a resistor in series with
the load is used as the control voltage ( F ig.4.1 b.). Similarly a reference
microphone can be used to control sound pressure or an accelerometer can
be used to control vibration level. Examples can be seen in the Applications
chapter.
__.. o------.--1
From
Oscillator
----.o-----1
From
Oscillator
To Compressor
Input
To Compressor
Input
a) Constant Voltage b) Constant Current
Fig.4.1.
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Constant voltage and constant current compressor
loops
To use the compressor loop proceed as follows:
1. Set up and calibrate the Oscillator as described above in A.
2. Set the MATCHING IMPEDANCE switch to the desired position.
3. Connect the load to LOAD terminals or to the ATTENUATOR OUTPUT
at the top of the instrument, see B or C.
4. Feed the control voltage to the COMPRESSOR INPUT terminal. If neces-
sary use an amplifier which has a linear frequency characteristic for the
amplification of the control signal, approximately 0.5 volt being required
for full utilization of the compressor. (See Fig.3.2).
5. Set COMPRESSOR VOLTAGE and OUTPUT LEVEL to maximum (fully
clockwise).
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