Mhz Adjustment; Operating Modes Of The Vertical Amplifi Er - Hameg HM1000 Manual

Prior to adjustment make sure that the trace rotation adjust-
ment was performed.
Connect the 10:1 probe to the input. Use dc coupling. Set
the VOLTS/DIV to 5 mV/cm and TIME/DIV to 0.2 ms/cm, both
calibrated. Insert the probe tip into the calibrator connector
PROBE ADJ.
You should see 2 signal periods. Adjust the compensation ca-
pacitor (see the probe manual for the location) until the square
wave tops are exactly parallel to the graticule lines (see picture
1 kHz). The signal height should be 4 cm ±1.6 mm (3% oscillo-
s-cope and 1% probe tolerance). The rising and falling portions
of the square wave will be invisible.

1 MHz adjustment

The HAMEG probes feature additional adjustments in the
compensation box which allow to optimise their hf behaviour.
This adjustment is a precondition for achieving the maximum
bandwidth with probe and a minimum of pulse aberrations.
This adjustment requires a calibrator with a short rise time
(typ. 4 ns) and a 50 Ω output, a frequency of 1 MHz, an amplitude
of 0.2 V . The PROBE ADJ. output of the scope fulfi ls these
pp
requirements.
Connect the probe to the scope input to which it is to be adjusted.
Select the PROBE ADJ. signal 1 MHz. Select dc coupling and 5
mV/cm with VOLTS/DIV. and 0.1 us/cm with TIME/DIV., both ca-
librated. Insert the probe tip into the calibrator output connector.
The screen should show the signal, rise and fall times will be
visible. Watch the rising portion and the top left pulse corner,
consult the manual for the location of the adjustments.
incorrect correct
The criteria for a correct adjustment are:
– short rise time, steep slope.
– clean top left corner with minimum over- or undershoot,
fl at top.
After adjustment check the amplitude which should be the
same as with 1 kHz.
It is important to fi rst adjust 1 kHz, then 1 MHz. It may be ne-
cessary to check the 1 kHz adjustment again.
Please note that the calibrator signals are not calibrated with
respect to frequency and thus must not be used to check the
time base accuracy, also their duty cycle may differ from 1:1.The
probe adjustment is completed if the pulse tops are horizontal
and the amplitude calibration is correct.
O p e r a t i n g m o d e s o f t h e v e r t i c a l a m p l i f i e r
Operating modes of the vertical amplifi er
The controls most important for the vertical amplifi er are:
VERT/XY
containing the operating modes and the parameters of the
individual channels.
Changing the operating mode is described in the chapter:
"Controls and Readout".
Remark:
Any reference to "both channels" always refers to channels
1 and 2.
Usually oscilloscopes are used in the Yt mode.The amplitude
of the measuring signal will defl ect the trace vertically while a
time base will defl ect it from left to right.
The vertical amplifi ers offer these modes:
– One signal only with CH1.
– One signal only with CH2.
– Two signals with channels 1 and 2 (DUAL trace mode)
In DUAL mode both channels are operative. The method of
signal display is governed by the time base (see also "Controls
and Readout"). Channel switching may either take place after
each sweep (alternate) or during sweeps with a high frequency
(chopped).
The normal choice is alternate, however, at slow time base set-
tings the channel switching will become visible and disturbing,
when this occurs select the chopped mode in order to achieve
a stable quiet display.
In ADD mode the two channels 1 and 2 are algebraically ad-
ded (±CH1 ±CH2). With + polarity the channel is normal, with
– polarity inverted. If + Ch1 and – CH2 are selected the difference
will be displayed or vice versa.
incorrect
Same polarity input signals:
Both channels not inverted: = sum
Both channels inverted:
Only one channel inverted:
Opposite polarity input signals:
Both channels not inverted: = difference
Both channels inverted:
One channel inverted:
Please note that in ADD mode both position con-
trols will be operative. The INVERT function will not
affect positioning.
Often the difference of two signals is to be measured at signal
STOP
take-offs which are both at a high common mode potential.
While this one typical application of the difference mode one
important precaution has to be borne in mind: The oscillosco-
pe vertical amplifi ers are two separate amplifi ers and do not
constitute a true difference amplifi er with as well a high CM
rejection as a high permissible CM range! Therefore please
observe the following rule: Always look at the two signals in
the one channel only or the dual modes and make sure that
they are within the permissible input signal range; this is the
case if they can be displayed in these modes. Only then switch
to ADD. If this precaution is disregarded grossly false displays
, CH1 , CH2 . They give access to the menus
= sum
= difference
= difference
= sum.
Subject to change without notice
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