11
Subject to change without notice
Controls and Readout
visible if the correct termination is not used. A terminating
resistance is sometimes recommended with sine signals as
well. Certain amplifiers, generators or their attenuators main-
tain the nominal output voltage independent of frequency only
if their connection cable is terminated with the prescribed
resistance. Here it must be noted that the terminating resistor
HZ22
will only dissipate a maximum of 2Watts. This power is
reached with 10Vrms or at 28.3Vpp with sine signal. If a x10
or x100 attenuator probe is used, no termination is necessary.
In this case, the connecting cable is matched directly to the high
impedance input of the oscilloscope. When using attenuators
probes, even high internal impedance sources are only slightly
loaded (approx. 10M
Ω
II 12pF or 100M
Ω
II 5pF with
HZ53
).
Therefore, if the voltage loss due to the attenuation of the
probe can be compensated by a higher amplitude setting, the
probe should always be used. The series impedance of the
probe provides a certain amount of protection for the input of
the vertical amplifier. Because of their separate manufacture,
all attenuator probes are only partially compensated, therefore
accurate compensation must be performed on the oscillo-
scope (see Probe compensation ).
Standard attenuator probes on the oscilloscope normally
reduce its bandwidth and increase the rise time. In all cases
where the oscilloscope bandwidth must be fully utilized (e.g.
for pulses with steep edges) we strongly advise using the
probes
HZ51
(x10)
HZ52
(x10 HF) and
HZ54
(x1 and x10). This
can save the purchase of an oscilloscope with larger band-
width.
The probes mentioned have a HF-calibration in addition to low
frequency calibration adjustment. Thus a group delay correc-
tion to the upper limit frequency of the oscilloscope is possible
with the aid of an 1MHz calibrator, e.g.
HZ60
.
In fact the bandwidth and rise time of the oscilloscope are not
noticably changed with these probe types and the waveform
reproduction fidelity can even be improved because the probe
can be matched to the oscilloscopes individual pulse re-
sponse.
If a x10 or x100 attenuator probe is used, DC input
coupling must always be used at voltages above 400V.
With AC coupling of low frequency signals, the atte-
nuation is no longer independent of frequency, pulses
can show pulse tilts. Direct voltages are suppressed
but load the oscilloscope input coupling capacitor
concerned. Its voltage rating is max. 400 V (DC + peak
AC). DC input coupling is therefore of quite special
importance with a x100 attenuation probe which usu-
ally has a voltage rating of max. 1200 V (DC + peak AC).
A capacitor of corresponding capacitance and voltage
rating may be connected in series with the attenuator
probe input for blocking DC voltage (e.g. for hum
voltage measurement).
With all attenuator probes,
the maximum AC input voltage
must be derated with frequency usually above 20kHz. There-
fore the derating curve of the attenuator probe type con-
cerned must be taken into account.
The selection of the ground point on the test object is
important when displaying small signal voltages. It should
always be as close as possible to the measuring point. If this
is not done, serious signal distortion may result from spurious
currents through the ground leads or chassis parts. The
ground leads on attenuator probes are also particularly critical.
They should be as short and thick as possible. When the
attenuator probe is connected to a BNC-socket, a BNC-
adapter, should be used. In this way ground and matching
problems are eliminated. Hum or interference appearing in
the measuring circuit (especially when a small deflection
coefficient is used) is possibly caused by multiple grounding
because equalizing currents can flow in the shielding of the
test cables (voltage drop between the protective conductor
connections, caused by external equipment connected to the
mains/line, e.g. signal generators with interference protec-
tion capacitors).
Controls and Readout
The following description assumes that the instru-
ment is not set to “COMPONENT TESTER” mode.
If the instrument is switched on, all important settings are
displayed in the readout. The LED´s located on the front panel
assist operation and indicate additional information. Incorrect
operation and the electrical end positions of control knobs are
indicated by a warning beep.
Except for the power pushbutton
(POWER)
, the calibrator
frequency pushbutton
(CAL. 1kHz/1MHz)
, the focus control
(FOCUS)
and the trace rotation control
(TR)
all other controls
are electronically selected. All other functions and their set-
tings can therefore be remote controlled and stored.
The front panel is subdivided into sections.
On the top, immediately to the right of the CRT screen,
the following controls and LED indicators are placed:
(1) POWER
- Pushbutton and symbols for
ON (I)
and
OFF
(O)
.
After the oscilloscope is switched on, all LEDs are lit and
an automated instrument test is performed. During this
time the
HAMEG
logo and the software version are
displayed on the screen. After the internal test is com-
pleted succesfully, the overlay is switched off and the
normal operation mode is present. Then the last used
settings become activated and one LED indicates the ON
condition.
Some mode functions can be modified
(SETUP)
and/or
automated adjustment procedures (CALIBRATE) can be
called if the
“MAIN MENU”
is present.
For further
information please note “MENU”
.
(2) AUTO SET
-
Briefly depressing this pushbutton (
please note “AUTO
SET”
) automatically selects Yt mode. The instrument is
set to the last used Yt mode setting (CH I, CH II or DUAL).
Even if alternating timebase mode or B timebase mode
was active before, the instrument is switched automati-
cally to A timebase mode.
Please note “AUTO SET”
.
Automatic CURSOR supported voltage measurement
If CURSOR voltage measurement is present, the CUR-
SOR lines are automatically set to the positive and
negative peak value of the signal. The accuracy of this
function decreases with higher frequencies and is also
influenced by the signal‘s pulse duty factor.
