Fig.9 Phase Measurements, X Y Method; Fig. 10 Frequency Measurements; Y Output Signal - Philips PM 3210 Operating Manual

Fig. 9. Phase measurements, X Y method
D2. Frequency measurement
To measure frequencies, a signal with a known, adjustable
frequency must be connected to input socket Ygp. The
signal with the frequency to be measured must be applied
to socket YA. Set the Y display-mode switch to X-Y and
proceed as follows:
1. adjust the known frequency to obtain a stable display;
2. imagine a horizontal and vertical tangent to the
obtained Lissajous figure;
3. count the points of contact nx of the trace and the
vertical tangent and the points of contact ny of the
trace and the horizontal tangent. If the Lissajous
figure is not closed, the point of contact of the tan-
gent with the open figure must be taken into
account as half a point of contact.
Example:
Assume that nx = 4, ny = 3 and that the known
frequency is 500 Hz (see Fig. 10).
Fig. 10. Frequency measurements
29
Using the formula:
n
unknown frequency = = (known frequency)
nx
= 3/4 x 500
= 375 Hz
E. Y OUTPUT SIGNAL
Many advantages accrue from the fact that in this
oscilloscope the internal triggering signal can be derived
from either channel and is taken off before the
electronic switch. The main advantages are:
— the trigger signal is merely a part of the input signal
and is, therefore, devoid of interfering components
such as are present in the chopped mode and may
result in display instability;
— in the alternate mode, the possibility of time relation-
ship errors between the displayed waveforms is
avoided since the trigger signal is not a combination of
two or more signals;
-- the triggering is unaffected by the continuous AMPL.
controls and the SHIFT/polarity controls of the
Y amplifiers;
— asimple method is provided for triggering from either
channel without the necessity of changing input
connections or applying one of the signals to the
external trigger input.
In this way misleading displays are prevented and a stable
display is obtained very easily.
Sometimes, however, it may be necessary to displaytwo
signals with unrelated frequencies. External triggeritg
with the Y signal of socket Y OUT, will then provid: a
stable display, when the instrument is operated in the
ALTERN. mode.
Example:
Assume that you want to adjust a frequency to be a
certain ratio of an accurately known frequency. Suppose
that the known frequency is exactly 2 MHz and thatthe
other frequency has to be adjusted to 5 MHz.
— Set the time base to display about 3 complete cydes
of the 2 MHz signal.
— Set the display switch to position ALTERN.
The input signals will be present at the Y output iocket
alternately for a complete sweep time.
~ Connect the Y output socket to socket TRIGG (U1).
The d.c. level of each signal can be varied by meais. of
the relevant SHIFT control.