13
Subject to change without notice
Operating modes of the vertical amplifi er
The controls most important for the vertical amplifi er are:
VERT/XY
32
, CH 1
31
, CH 2
33
. They give access to the menus
containing the operating modes and the para0meters of the
individual channels.
Changing the operating mode is described in the chapter:
”Controls and Readout“.
Remark: Any reference to ”both channels“ always refers to
channels 1 and 2.
Usually oscilloscopes are used in the Yt mode. In analog mode
the amplitude of the measuring signal will defl ect the trace
vertically while a time base will defl ect it from left to right.
The vertical amplifi ers offer these modes:
– One signal only with CH1.
– One signal only with CH2.
– Two signals with channels 1 and 2 (DUAL trace mode)
In DUAL mode both channels are operative. In analog mode
the method of signal display is governed by the time base (see
also ”Controls and Readout“). Channel switching may either
take place after each sweep (alternate) or during sweeps at
high frequency (chopped).
The normal choice is alternate, however, at slow time base set-
tings the channel switching will become visible and disturbing,
when this occurs select the chopped mode in order to achieve
a stable quiet display.
In DIGITAL mode no channel switching is necessary as each
input has its own A/D converter, signal acquisition is simul-
taneous.
In ADD mode the two channels 1 and 2 are algebraically ad-
ded (±CH1 ±CH2). With + polarity the channel is normal, with
– polarity inverted. If + Ch1 and – CH2 are selected the difference
will be displayed or vice versa.
Same polarity input signals:
Both channels not inverted:
= sum
Both channels inverted:
= sum
Only one channel inverted:
= difference
Opposite polarity input signals:
Both channels not inverted:
= difference
Both channels inverted:
= difference
One channel inverted:
= sum.
Please note that in ADD mode both position controls will be
operative. The INVERT function will not affect positioning.
Often the difference of two signals is to be measured at signal
points which are both at a high common mode (CM) potential.
While this one typical application of the difference mode one
important precaution has to be borne in mind: The oscilloscope
vertical amplifiers are two separate amplifiers and do not con-
stitute a true difference amplifier with both a high CM rejection
and a high permissible CM range! Therefore please observe the
following rule: Always look at the two signals in the one channel
only or the dual modes (not in Add mode) and make sure that
they are within the permissible input signal range; this is the
case if they can be displayed in these modes. Only then switch
to ADD. If this precaution is disregarded grossly false displays
the VOLTS/DIV to 5 mV/cm and TIME/DIV to 0.2 ms/cm, both
calibrated. Insert the probe tip into the calibrator connector
PROBE ADJ.
You should see 2 signal periods. Adjust the compensation ca-
pacitor (see the probe manual for the location) until the square
wave tops are exactly parallel to the graticule lines (see picture
1 kHz). The signal height should be 4 cm ±1.6 mm (3% oscillo-
scope and 1% probe tolerance). The rising and falling portions
of the square wave will be invisible.
1 MHz adjustment
The HAMEG probes feature additional adjustments in the
compensation box which allow you to optimise their hf be-
haviour. This adjustment is a precondition for achieving the
maximum bandwidth with the probe and a minimum of pulse
aberrations.
This adjustment requires a calibrator with a short rise time
(typ. 4 ns) and a 50 Ω output, a frequency of 1 MHz, an amplitude
of 0.2 V
pp
. The PROBE ADJ. output of the scope fulfi ls these
requirements.
Connect the probe to the scope input with which it is to be adju-
sted. Select the PROBE ADJ. signal 1 MHz. Select DC coupling and
5 mV/cm with VOLTS/DIV. and 0.1 μs/cm with TIME/DIV., both
calibrated. Insert the probe tip into the calibrator output con-
nector. The screen should show the signal, and the rise and
fall times will be visible. Watch the rising portion and the top
left pulse corner, consult the manual for the location of the
adjustments.
The criteria for a correct adjustment are:
– short rise time, steep slope.
– clean top left corner with minimum over or undershoot, fl at
top.
After adjustment check the amplitude which should be the
same as with 1 kHz.
It is important to fi rst adjust 1 kHz, then 1 MHz. It may be ne-
cessary to check the 1 kHz adjustment again.
Please note that the frequency of the calibrator signals is not
calibrated and thus must not be used to check the time base
accuracy, also the duty cycle may differ from 1:1.The probe
adjustment is completed if the pulse tops are horizontal and
the amplitude calibration is correct.
O p e r a t i n g m o d e s o f t h e v e r t i c a l a m p l i f i e r
incorrect
correct
incorrect
