Subject to change without notice
12
The adjustment sequence must be followed in the order
described, i.e. first at 1kHz, then at 1MHz. The calibrator
frequencies should not be used for timebase calibration. The
pulse duty cycle deviates from 1:1 ratio.
Prerequisites for precise and easy probe adjustments, as well
as checks of deflection coefficients, are straight horizontal
pulse tops, calibrated pulse amplitude, and zero-potential at
the pulse base. Frequency and duty cycle are relatively
uncritical. For interpretation of transient response, fast pulse
risetimes and low-impedance generator outputs are of
particular importance.
Providing these essential features, as well as switch-
selectable output-frequencies, the calibrator of the HM304
can, under certain conditions, replace expensive squarewave
generators when testing or compensating wideband-
attenuators or -amplifiers. In such a case, the input of an
appropriate circuit will be connected to one of the
CAL.
-
outputs via a suitable probe.
The voltage provided at a high-impedance input (1M
Ω
II 15-
30pF) will correspond to the division ratio of the probe used
(10:1 = 20mVpp, 100:1 = also 20mVpp from 2V output).
Suitable probes are HZ51, 52, 53, and 54.
Operating modes of the vertical
amplifiers in Yt mode.
The vertical amplifier is set to the desired operating mode by
using the 2 pushbuttons
CH I
and
CH II
(for
CH I
,
CH II
,
DUAL
and
ADD
mode) in the Y field of the front panel. The
different modes are indicated by LED‘s in the
channel I
and
channel II
VOLTS/DIV
sections and the
ADD LED
in ADD
mode.
If only
CH II
is active to switch to CH I mode, first press the
CH I
pushbutton to switch on channel I. Now the oscilloscope
is in
DUAL
mode where LED‘s in both
VOLTS/DIV
sectors
are lit. Then the CH II pushbutton must be depressed once
to switch off channel II. It is not possible to operate the
oscilloscope with both channels switched off. That is why
the required channel must first be switched on and then the
unwanted channel must be switched off.
To switch from CH I to CH II mode, first switch on CH II and
then switch off CH I. If internal triggering is selected (EXT
LED near the
TRIG. INP.
socket extinguished), the trigger
source indicator LED‘s (
TR I
and
TR II
) will be switched over
simultaneously.
DUAL
mode is selected if a LED is lit in each
VOLTS/DIV
sectors. As mentioned before, one channel is always present
and so the other channel must be switched on for DUAL
mode operation.
In
DUAL
mode both channels are working. Two signals can
be displayed together in alternate or chopped mode. The
alternate mode is not suitable for displaying very slow-running
processes. The display then flickers or appears to jump.
Therefore the instrument automatically switches over from
alternate to chopped mode if
TIME/DIV
settings from 0.5ms/
div to 0.5s/div are used. If in chopped DUAL mode, both
channels are switched over constantly at a high frequency
within a sweep period. Low frequency signals below 1kHz,
or with periods longer than 1ms are then displayed without
flicker. Conversely in
DUAL
alternate mode, the displayed
channel switches over from channell I to channel II and vice
versa after each sweep period.
In DUAL mode the internal trigger source can be switched
over from channel I to channel II and vice versa if the
TRIG.
pushbutton is depressed for a short time. Depressing the
TRIG.
pushbutton in DUAL mode for a longer time switches
over to alternate triggering and consequently both TR I and
TR II LED‘s are lit. As alternate triggering is not possible in
combination with DUAL chopped mode, the instrument
automatically switches over to the alternate mode if DUAL
chopped mode was active before. Alternate triggering can
be switched off by depressing the
TRIG.
pushbutton for a
short time. Then just one TR LED is lit.
DUAL
chopped mode is also automatically switched off when
TV-F (television frame triggering) is selected to avoid
interference.
In combination with delay and triggered delay mode, DUAL
chopped mode can also be switched to DUAL alternate mode
by simultaniously depressing both pushbuttons marked with
< and > arrows in the TIME/DIV sector. Any change in the
delay mode time base setting reverts to the DUAL chopped
mode.
ADD mode is selected by simultaneously depressing both
CH I
and
CH II
pushbuttons which causes the
ADD LED
between both pushbuttons to light.
In
ADD
mode the signals of both channels are algebraically
added (±I ±II) and displayed as one signal. Whether the
resulting display shows the sum or difference is dependent
on the phase relationship or the polarity of the signals and on
the invert function indicated by the
INV LED‘s
for each
channel. To quit the
ADD
mode, depress the pushbutton for
the required channel or depress both CH I and CH II
pushbuttons for a short time to switch back to DUAL mode.
As alternate triggering is not available in ADD mode, the
instrument switches over from ADD mode to alternate DUAL
mode if the TRIG pushbutton is depressed for a longer time.
In
ADD
mode the following combinations are possible for
In-phase input voltages:
• Both INV (invert) function CH.I and
INV (invert) function CH.II active
• released or depressed = sum.
• Only one INV (invert) function active = difference.
Antiphase input voltages:
• Both INV (invert) function active
or inactive = difference.
• INV (invert) function CH.I or INV
(invert) function CH.II active = sum.
In the
ADD
mode the vertical display position is dependent
upon the
Y-POS.
setting of both channels. The same Y
deflection coefficient is normally used for both channels with
algebraic addition.
Please note that the Y-POS. settings are also added
but are not affected by the INV setting.
Differential measurement techniques allow direct
measurement of the voltage drop across floating components
(both ends above ground). Two identical probes should be
used for both vertical inputs. In order to avoid ground loops,
use a separate ground connection and do not use the probe
ground leads or cable shields.
X-Y Operation
For X-Y operation, the pushbutton in the X field marked XY
must be depressed. Then the XY LED in the
TIME/DIV
sector
is lit and the time coefficient indication is switched off. The X
signal is then derived from the
INPUT CH II (X)
. The
calibration of the X signal during X-Y operation is determined
by the setting of the Channel II Y deflection coefficient and
variable control.
This means that the sensitivity ranges and input impedances
