12
Subject to change without notice
onscreen. If calibrated measurements are desired it will be
necessary to use a probe if the signal becomes
>
40 V
pp
. Check
the probe specifi cations in order to avoid overstressing. If the
time base is set too fast the trace may become invisible, then
reduce the time base speed.
If no probe is used at least screened cable should be used,
such as HZ32 or HZ34. However, this is only advisable for low
impedance sources or low frequencies (
<
50 kHz). With high
frequencies impedance matching will be necessary.
Non sinusoidal signals particularly require impedance matching,
preferably at both ends. At the scope input, a 50 Ω termination is
selectable with a maximum load of 0.5 Watt (5 V
rms
, or in case of
sine wave signals, 14.7 V
pp
). If proper terminations are not used,
sizeable pulse aberrations will result. Also sine wave signals
of
>
100 kHz should be properly terminated. Most generators
control signal amplitudes only if correctly terminated.
For higher loads (up to 1 Watt; 7 V
rms
or 20 V
pp
) HAMEG offers
the external 50 Ω termination HZ22.
For probes terminations are neither required nor allowed, they
would ruin the signal.
Probes feature very low loads at fairly low frequencies: 10 MΩ
in parallel to a few pF, valid up to several hundred kHz. How-
ever, the input impedance diminishes with rising frequency to
quite low values. This has to be borne in mind as probes are,
e.g., entirely unsuitable to measure signals across high impe-
dance high frequency circuits such as bandfi lters etc.! Here
only FET probes can be used. Use of a probe as a rule will also
protect the scope input due to the high probe series resistance
(9 MΩ). As probes cannot be calibrated exactly enough during
manufacturing individual calibration with the scope input used
is mandatory! (See Probe Calibration).
Passive probes will, as a rule, decrease the scope bandwidth
resp. increase the rise time. We recommend to use HZ200 pro-
bes in order to make maximum use of the combined bandwidth.
HZ200 features 2 additional hf compensation adjustments.
Whenever the DC content is
>
250 V
DC
coupling must be used in
order to prevent overstressing the scope input capacitor. This is
especially important if a 100:1 probe is used as this is specifi ed
for 1200 V
DC
+ peak AC.
AC coupling of low frequency signals may produce tilt.
If the DC content of a signal must be blocked it is possible to
insert a capacitor of proper size and voltage rating in front of the
probe, a typical application would be a ripple measurement.
When measuring small voltages the selection of the ground
connection is of vital importance. It should be as close to voltage
take-off point as possible, otherwise ground currents may de-
teriorate the measurement. The ground connections of probes
are especially critical, they should be as short as possible and
of large size.
STOP
If a probe is to be connected to a BNC connector use
a probe tip to BNC adapter.
If ripple or other interference is visible, especially at high sen-
sitivity, one possible reason may be multiple grounding. The
scope itself and most other equipment are connected to safety
ground, so ground loops may exist. Also, most instruments will
have capacitors between line and safety ground installed which
conduct current from the live wire into the safety ground.
First time operation and initial adjustments
Prior to fi rst time operation the connection between the instru-
ment and safety ground must be ensured, hence the plug must
be inserted fi rst.
Use the red pushbutton POWER to turn the scope on. Several
displays will light up. The scope will then assume the set-up,
which was selected before it was turned off. If no trace and
no readout are visible after approximately 20 sec, push the
AUTOSET button.
As soon as the trace becomes visible select an average inten-
sity with INTENS, then select FOCUS and adjust it, then select
TRACE ROTATION and adjust for a horizontal trace.
With respect to crt life use only as much intensity as necessary
and convenient under given ambient light conditions, if unused
turn the intensity fully off rather than turning the scope off and
on too much, this is detrimental to the life of the crt heater.
Do not allow a stationary point to stay, it might burn the crt
phosphor.
With unknown signals start with the lowest sensitivity 5 V/cm,
connect the input cables to the scope and then to the measu-
ring object which should be deenergized in the beginning. Then
turn the measuring object on. If the trace disappears, push
AUTOSET.
Trace rotation TR
The crt has an internal graticule. In order to adjust the defl ected
beam with respect to this graticule the Trace Rotation control
is provided. Select the function Trace Rotation and adjust for a
trace which is exactly parallel to the graticule.
Probe adjustment and use
In order to ensure proper matching of the probe used to the
scope input impedance the scope contains a calibrator with
short rise time and an amplitude of 0.2 Vpp ± 1 %, equivalent
to 4 cm at 5 mV/cm when using 10:1 probes.
The inner diameter of the calibrator connector is 4.9 mm and
standardized for series F probes. Using this special connec-
tor is the only way to connect a probe to a fast signal source
minimizing signal and ground lead lengths and to ensure true
displays of pulse signals.
1 kHz – adjustment
This basic adjustment will ensure that the capacitive at-
tenuation equals the resistive attenuation thus rendering the
attenuation of the probe independent of frequency. 1:1 probes
can not be adjusted and need no such adjustment anyway.
F i r s t t i m e o p e r a t i o n a n d i n i t i a l a d j u s t m e n t s
incorrect
correct
incorrect
