Table of Contents
Advertisement
other 2Vpp ±1% for xlOO attenuator probes. These volt¬
ages correspond in each case to a screen amplitude of 4
div.
provided the input attenuator switch of the HM 203-7 is
set to the deflection coefficient 5 mV/div.
1 kHz compensation
This trimmer adjustment compensates the capacitive load¬
ing of the oscilloscope input (approx, 25 pF for the HM 203-7).
After compensation, the capacitive attenuation has the
same attenuation ratio as the ohmic divider. The same volt¬
age attenuation then results at high and low frequencies as
for direct voltage (for x1 probes or probes switches over to
x1, this compensation is neither necessary nor possible).
The trace line must be parallel with the horizontal graticule
lines (see "Trace rotation TR", page M7).
Connect attenuator probe (10:1 or 100:1) to the CH.I input,
do not press any buttons or turn any knobs, set input cou¬
pling to DC, input attenuator to 5 mV/div. and TIME/DIV.
switch to 0.2 ms/div. (both variable controls in calibration
position CAL), connect probe to the corresponding CAL.
eyelet (x10 probe to 0.2 V eyelet, x100 to 2 V eyelet).
2 cycles can be seen on the screen. The compensation trim¬
mer must now be adjusted. It is generally located in the
probe itself. It is located in the x100 attenuator probe HZ53
in the small box on the BNC plug. Adjust the trimmer with
the insulating screw driver provided until the tops of the
square wave signal are exactly parallel to the horizontal
graticule lines (see 1 kHz diagram). The signal height should
then be 4 div. ±0.12 div. (= 3 %). The signal edges are invis¬
ible during this adjustment.
1 MHz compensation
HF adjustment is possible for the HZ51,52, and 54 probes.
These possess resonance correction elements (pots in
combination with coils and capacitors) with which it is pos¬
sible for the first time to simply adjust the probe in the upper
frequency range of the vertical amplifier.
After this compensation, not only the maximum possible
bandwidth is obtained in the attenuator probe mode but
also a largely constant group delay at the end of the
bandwidth. In this way transient distortions (such as over¬
shooting, rounding off, ringing, holes or humps in the pulse
top) in the vicinity of the leading edge are kept to a
minimum. The bandwidth of the HM 203-7 is therefore fully
utilized when using the HZ51, 52 and 54 probes without
having to accept wave form distortions.
Prerequisite for this HF compensation is a square wave
generator with short rise time (typically 4 ns) and low-
impedance output (approx. 50 Ohm) which also supplies a
voltage of 0.25 V or 2.5 V at a frequency of 1 MHz.
The Scope Tester HZ60 fullfills these tasks excellently
(see Accessories, page Z1).
Operating modes of the vertical amplifiers
The desired operating mode of the vertical amplifiers is
selected with the 3 buttons in the Y field. All three buttons
out for
mono
mode. Only
Channel I
is then operational.
The button CHI /CHII must be depressed in mono mode for
Channel II.
The internal triggering is simultaneously
switched over to Channel II with this button.
If the DUAL button is depressed, both channels are work¬
ing. Two signals can be displayed together in this button
position (alternate mode). This mode is not suitable for dis¬
playing very slow-running processes. The display then flick¬
ers too much or it appears to jump. If the CHOP, button is
depressed in addition to DUAL, both channels are switched
over constantly at a high frequency within a sweep period
(CHOP mode). Slow running processes
below 1 kHz or
with time coefficients higher than 1 ms/cm
are then also
displayed without flicker. The dual mode chosen is less
important for signals with higher repetition frequency.
If the ADD button is depressed, the signals of both chan¬
nels are algebraically added (I ± II). Whether the resulting
display shows the
sum
or
difference
is dependent on the
phase relationship or the polarity of the signals
and on
the
position of the INVERT button.
In-phase input voltages:
INV. CHII button released = sum.
INV. CHII button depressed = difference.
Antiphase input voltages:
INV. CHII button released = difference.
INV. CHII button depressed = sum.
In the ADD mode the vertical display position is dependent
upon the Y-POS. setting of
both
channels. The
same
attenuator switch position
is normally used for both chan¬
nels with algebraic addition.
Differentiai
measure/nenf techniques allow direct meas¬
urement of the voltage drop across floating components
(both ends above ground). Two identical probes should be
used for both vertical inputs. Using a separate ground con¬
nection and not connecting the probe or cable shields to the
circuit under test avoid ground loops (hum, common-mode
disturbances).
M8 203-7
Subject to change without notice
Advertisement
Table of Contents
