35
Subject to change without notice
STOP
Please
note:
The sensitivity control is always active, i.e. also if
CH2 is not selected. CH2 may then still be used e.g.
as a trigger source.
17.2 Variable control
This function can be activated by pressing the CH2 VAR push-
button
33
and selecting On by the “Variable“ function key.
The the CH2 VAR pushbutton
33
lights and indicates that the
VOLTS/DIV–SCALE–VAR knob
17
now serves as Variable control.
Thereafter the defl ection coeffi cient can be changed continuous-
ly between 1 mV/cm and
>
5 V/cm the range is (automatic probe)
factor or (manual probe setting) dependent) and thus the the
signal display height.
If uncalibrated, the defl ection coeffi cient will be displayed as
e.g. “...
>
5mV...“ and correspondingly the results of cursor
voltage measurement. In calibrated conditon e.g. “...:5mV...“
will be displayed.
If variable “off“ is activated in the CH2 menu, the defl ection
coeffi cient becomes calibrated, the CH2 VAR pushbutton
33
does not light any longer and the VOLTS/DIV–SCALE–VAR knob
17
returns to 1-2-5 sequence.
17.3 Scaling the FFT display
(digital mode only)
17.3.1
Preliminary note:
To avoid erroneous spectrum displays, it must be checked before
switching over to FFT, that the Yt (time base) signal display is sui-
ted for calculation in FFT. This means that the time base setting
(sampling rate) must enable the display of minimum one signal
period; in case of complex signals this is regarding the signal with
the lowest frequency. On the other hand the sampling rate must
not be too low (too many signal periods) to avoid so called aliasing.
The signal display height should be between 5 mm (0.5 div.) and
8 cm (8 div.). Signal display heights
>
8 cm, cause the danger
that the dynamic range is exceeded, so that signals deformed
by limiting effects to square wave form, become digitised and at
least show spectrum displays spectra that do not exist in reality.
If the sampling rate is too low the readout displays “ALS“; if the
signal is too high “overrange ±“ will be displayed.
Such problems can be avoided, by pressing the AUTOSET push-
button
11
before switching over to FFT or during FFT mode.
17.3.2
Scaling:
In FFT mode the VOLTS/DIV–SCALE–VAR knob
17
only chan-
ges the scaling of the spectrum display; this means that the
spectrum (including noise) is displayed in double height after
switching over from 20 dB/cm to 10 dB/cm. The previously in Yt
mode selected Y defl ection coeffi cient is thereby not affected.
If dBV is set in the FFT menu, the scaling is switched over from
5dB/cm to 500dB/cm in 1-2-5 sequence by the VOLTS/DIV–SCA-
LE–VAR knob
16
; at V
(rms)
the range is from 5mV/cm to 20V/cm
also switched in 1-2-5 sequence. Please note that in contrast
to Yt- and XY mode signal display, no peak to peak values but
rms values are displayed.
18
AUTO MEASURE
(pushbutton)
AUTO MEASURE can not be called if XY or FFT mode is pre-
sent.
On condition that the AUTO MEASURE function was switched
off, it will be switched on by pressing the AUTO MEASURE
pushbutton and simultaneously the AUTO MEASURE measuring
results are displayed in the top right position of the readout
below trigger information.
Pressing the AUTO MEASURE pushbutton for the second time,
opens the menu “Measure“ and a selection box. Additionally
the FOCUS TRACE MENU pushbutton light, indicating that the
INTENS knob
2
now has a function related to the menu item
selected in the “Measure“ menu.
The measuring result is displayed by the readout in top right
position, one line below trigger source, slope and coupling.
Dependent on the mode, different measurements are offered
in this menu, all relate to the trigger signal.
In principle the following conditions must be met:
a) Trigger conditions must be present if frequency or period
time measurement is performed. For signals under 20 Hz
normal triggering is required. Please note that very low fre-
quency signals require several seconds measuring time.
b) DC input and DC trigger coupling must be present if DC
voltages or the DC content of signals which contain DC and
AC the DC content are to be measured.
Please note:
– Due to the frequency response of the trigger amplifi er the
measuring accuracy decreases at higher frequencies.
– Related to the signal display there are deviations originating
from the different frequency response of the Y measuring
amplifi er and the trigger amplifi er.
– The measuring result follows the signal form when low
frequency (
<
20 Hz) voltages are measured.
– Measuring pulse shaped voltages cause deviations between
the real and the displayed values. The deviation height de-
pends on the pulse ratio and the selected trigger slope.
– The signal to be measured must be displayed within the
graticule limits to avoid measuring errors.
– On condition the variable function is switched on the … VAR
pushbutton is lit, the defl ection coeffi cient and/or the time
base are/is uncalibrated and a “
>
“ sign is displayed by the
readout in front of the defl ection coeffi cient. The results of
voltage and/or time/frequency measurement are labelled
in the same way.
STOP
Attention!
Due to the danger of mismeasurement, complex
signals should be measured by aid of the cursors.
C o n t r o l s a n d R e a d o u t
FFT-
Marker
VAR
x10
TIME / DIV
SCALE
·
VAR
X-POS
LEVEL A/B
50s
2ns
LC/AUX
FFT
HORIZONTAL
DELAY
MODE
FILTER
SOURCE
TRIG
’
d
NORM
HOLD OFF
TRIGGER
HOR
MAG
POWER
MENU
OFF
19
26
27
20
23
21
24
28
22
25
29
30
