24
Subject to change without notice
Connect the probes (
Types HZ51, 52, 54,
or
HZ36
) to the
CH
I
input. Set the deflection coefficient to 5mV/div and the input
coupling to DC. The time deflection coefficient should be set
to 0.2ms/div. All deflection coefficients should be calibrated.
Plug the probe tip into the calibrator output socket.
Approximately 2 complete waveform periods are displayed on
the CRT screen. The compensation trimmer should be adjusted.
The location of the low frequency compensation trimmer can
be found in the probe information sheet. Adjust the trimmer
with the insulated screw driver provided, until the tops of the
square wave signal are exactly parallel to the horizontal graticule
lines (see 1kHz diagram). The signal height should then be 4div
± 0.16div (= 4% (oscilloscope 3% and probe 1%). During this
adjustment, the signal edges will remain invisible.
Adjustment at 1MHz
Probes
HZ51
,
52
and
54
can also be HF-compensated. They
incorporate resonance de-emphasing networks (R-trimmer in
conjunction with inductances and capacitors) which permit
probe compensation in the range of the upper frequency limit
of the vertical oscilloscope amplifier. Only this compensative
adjustment ensures optimum utilization of the full bandwidth,
together with constant group delay at the high frequency end,
thereby reducing characteristic transient distortion near the
leading edge (e.g. overshoot, rounding, ringing, holes or
bumps) to an absolute minimum.
Using the probes
HZ51
,
52
and
54
, the full bandwidth of the
oscilloscope can be utilized without risk of unwanted waveform
distortion.
Prerequisite for this HF compensation is a square wave
generator with fast risetime (typically 4ns), and low output
impedance (approx. 50
Ω
), providing 0.2V at a frequency of
approx. 1MHz. The calibrator output of this instrument meets
these requirements when the
CAL.
pushbutton is depressed.
Connect the probe to CH.I input. Depress the
CAL.
pushbutton
for 1MHz. Operate the oscilloscope as described under 1kHz
but select for 0.2µs/div time deflection coefficient setting.
Insert the probe tip into the output socket. A waveform will be
displayed on the CRT screen, with leading and trailing edges
clearly visible. For the HF-adjustment now to be performed, it
will be necessary to observe the rising edge as well as the
upper left corner of the pulse top. The location of the high
frequency compensation trimmer(s) can also be found in the
probe information sheet. These R-trimmer(s) have to be
adjusted such that the beginning of the pulse is as straight as
possible. Overshoot or excessive rounding are unacceptable.
The adjustment is relatively easy if only one adjusting point is
present. In case of several adjusting points the adjustment is
slightly more difficult, but causes a better result. The rising
edge should be as steep as possible, with a pulse top remaining
as straight and horizontal as possible.
After completion of the HF-adjustment, the signal amplitude
displayed on the CRT screen should have the same value as
during the 1kHz adjustment.
Probes other than those mentioned above, normally have a
larger tip diameter and may not fit into the calibrator output.
Whilst it is not difficult for an experienced operator to build a
suitable adapter, it should be pointed out that most of these
probes have a slower risetime with the effect that the total
bandwidth of scope together with probe may fall far below that
of the oscilloscope. Furthermore, the HF-adjustment feature
is nearly always missing so that waveform distortion can not
be entirely excluded. The adjustment sequence must be
followed in the order described, i.e. first at 1kHz, then at
1MHz. The calibrator frequencies should not be used for time
base calibration. The pulse duty cycle deviates from 1:1 ratio.
Prerequisites for precise and easy probe adjustments, as well
as checks of deflection coefficients, are straight horizontal
pulse tops, calibrated pulse amplitude, and zero-potential at
the pulse base. Frequency and duty cycle are relatively uncritical.
For interpretation of transient response, fast pulse risetimes
and low-impedance generator outputs are of particular
importance.
Providing these essential features, as well as switch-selectable
output-frequencies, the calibrator of the instrument can, under
certain conditions, replace expensive squarewave generators
when testing or compensating wideband-attenuators or -
amplifiers. In such a case, the input of an appropriate circuit will
be connected to the CAL.-output via a suitable probe.
The voltage provided at a high-impedance input (1M
Ω
II 15-
30pF) will correspond to the division ratio of the probe used
(10:1 = 20mVpp output). Suitable probes are HZ51, 52, and 54.
Operating modes of the vertical
amplifiers in Yt mode
The most important controls regarding the operation modes of
the vertical amplifiers are the pushbuttons:
CH I (21)
,
DUAL
(22)
and
CH II (25)
.
Their functions are described in the section
“ Controls and readout”.
In most cases oscilloscopes are used to display signals in Yt
mode. Then the signal amplitude deflects the beam in vertical
direction while the time base causes an X deflection (from left
to right) at the same time. Thereafter the beam becomes
blanked and fly back occurs.
The following Yt operation modes are available:
Single channel operation of channel I (Mono CH I).
Single channel operation of channel II (Mono CH II).
Two channel operation of channel I and channel II (DUAL).
Two channel operation of channel I and channel II -displaying
the algebraic result as the sum or difference -
(ADD)
.
The way the channel switching is determined in DUAL mode
depends on the time base setting and is described in the
section “Controls and readout”.
In
ADD
mode the signals of both channels are algebraically
added and displayed as one signal. Whether the resulting
display shows the sum or difference is dependent on the
phase relationship or the polarity of the signals and on the
invert function.
In ADD mode the following combinations are possible for
In-phase input voltages:
No invert function active = sum.
Channel II invert function active = difference.
First Time Operation
