23
Subject to change without notice
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 screwdriver 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 rise time (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 unaccept able. 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 gives 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
rise time 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 rise times 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 square wave 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 (18)
,
DUAL (19)
and
CH II (22)
. 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
Operating modes
