Applications; Amplitude Measurements; Differential Measurements - Philips Pm 3342 Manual

15
Applications
A. AMPLITUDE MEASUREMENTS
When measuring the amplitude of a signal, use is made
of the calibrated deflection coefficients of the Y-de-
flection system (SK4; SK10).
Intermediate, non-calibrated deflection coefficients
can be obtained by operating R3 and R5.
With the aid of the controls of the basic oscilloscope
.and the plug-in unit, make a triggered display visible.
Check the zero level by means of button CHECK
~ VLcm
ZERO (SK1; SK7). (When the trigger-mode switch is
in the AUT. position, the time-base line will remain
visible during depression of push-button CHECK
ZER®. When a different position is used, the time-base
generator should be adjusted to its free-running posi-
tion by means of the STAB. control).
The amplitude of the total signal is then equal to the
product of deflection coefficient and the vertical de-
flection in cm.
Amplitude: 0.5 V/cm x 3.4 cm = 1.7 V.
When only the AC-voltage should be measured, the
DC-component can be removed from the signal with
the aid of the AC-DC switch.
If measurements have been carried out via measuring
probe PM 9331 A/10, the deflection coefficient of the
V/cm switch should be multiplied by a factor 10.
'The accuracy of the measurement can be increased by
precisely adjusting the deflection coefficient with the
GAIN control in the relevant position of the V/cm
knob.
For this, the calibration voltage of the basic oscillo-
scope can be used.
B. DIFFERENTIAL MEASUREMENTS
With these measurements, use is made of the common
mode rejection of the amplifiers in position ADDED.
When the polarity switches are set to opposite posi-
tions, two common mode signals on sockets A and B
will undergo a very slight amplification with respect
to two signals in anti-phase.
The signals on sockets A and B should not exceed a
value corresponding to a trace height of IO cm.
This common mode rejection can be adjusted to maxi-
mum by adjusting the amplifiers in such a way that
their amplifications for the signal to be measured are
exactly identical.
3.4cm
0-niveau