Accessories; Description Of The Block Diagram - Philips PM 5125 Manual

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Accessories
Manual
Optional accessories
Coupling kit PM 9500.
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- A selection of 5 different cover kits PM 9502... PM 9506.
- Rack-mounting kit PM 9510 for mounting a 6 -module cabinet into a
19" rack.
- Extension test board 4822 466 10165 for carrying out measurements
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on the plug-in printed wiring boards while the instrument is in
■`
operation.
The description and ordering information of these accessories are given
in chapter XIV of this manual.
Description of the block diagram
(See Fig. 3)
This instrument contains aphase-shift oscillator, an amplifier, a squarer,
a voltmeter, two attenuators and a double power supply.
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OSCILLATOR
The phase-shift oscillator consists of three unity gain amplifier stages.
The first two amplifier stages give each aphase-shift of 90° for the
oscillating frequency and the third amplifier stage gives aphase-shift of
180°. The output signal of the third amplifier stage is fed back to the
input of the first amplifier stage.
The amplifier stages are coupled by means of impedance converters
(emitter followers).
The unny loop gain is maintained by means of a thermistor, which is a r'
part of the collector impedance of the third amplifier stage.
FREQ. Hz(SK3, Rlr - Rlrt) ~('
The frequency of the oscillator may be varied continuously by means of
the double potentiometer Rlt - Rl~t and in steps of one decade by
means of the switch SK3.
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