Phase Measurements; Single Time-Base - Philips Pm 3342 Manual

16
Channel A
~~
PEM 2900
Channel B
For this, simultaneously apply one of the signals to
sockets A and B. Adjust the GAIN control in such a
way that a minimum trace height is obtained on the
screen.
After this, the common mode rejection will meet the
value mentioned in the technical data.
C. PHASE MEASUREMENTS
If the phase difference between two signals is to be
measured, the phase equality of both amplifiers of the
PM 3342 is used.
It is recommended to set the MODE selector to posi-
tion ALTERNATE. With low repetion frequencies
of the time-base generator, this working mode results
in a flickering display; in these cases the CHOPPED
position should be used.
A high chopper frequency may lead to mutual influence
of the two signals; therefore, it is recommended to set
the frequency switch to the 20 kc/s position.
The signals are applied to socket A or B respectively.
Make a triggered display visible with the controls of
the basic oscilloscope and the PM 3342.
Both traces should be adjusted exactly symmetrical
with respect to the centre horizontal graticule line.
The phase difference can be read directly in degrees by
adjusting knob TIME/cm (step- and continuous control
of the basic oscilloscope) in such a way that one period
of the signal to be measured corresponds to a whole
number of centimetres on the screen.
D. SINGLE TIME-BASE
If the signal to be measured requires the use of the
single-sweep display of the basic oscilloscope, the
MODE switch of the PM 3342 should be set to position
CHOPPED.
Selection of the switching frequency depends on the
time coefficient of the X-deflection.
V/cm, of both channels: identical
Polarity of channel A: INVERT.
Polarity of Chanel B: NORMAL
MODE in position: ADDED
Generally, the highest chopper frequency will be used;
for the lower time-base speeds however, also the lowest
chopper frequency can be selected.
Set the controls in the TIME BASE A frame to the
desired positions.
When the time-base generator is adjusted to its free-
running position (STAB. control to REPET), it will
start immediately after depressing push-button RESET.
When the STAB. control is in the trigger position,
the time-base generator will start on the first trigger
pulse, after depressing the RESET button.
During the time between depression of the RESET
knob and starting of the time-base generator, the
lamp in the RE5ET knob will light up.
PEM 2899
1 period = 9 cm
phase coefficient = 40°/cm
phase angle cp = 40°/cm x 1.6 cm = 64°