21
Subject to change without notice
(27) TRIG. MODE
- Pushbutton with double function and
indicator LEDs.
Pressing the upper or lower pushbutton selects the
trigger coupling
. The actual setting is indicated by a
LED and by the readout (“
TR: source, slope, AC
”).
Each time the lower
TRIG. MODE
pushbutton is pressed
the trigger coupling changes in the sequence:
AC
(DC content suppressed),
DC
(peak value detection inactive),
HF
(high-pass filter cuts off frequencies below
approx. 50kHz)
trigger point symbol switched off,
NR
(high frequency noise rejected),
LF
(low-pass filter cuts off frequencies above
approx. 1.5kHz),
TVL
(TV signal, line pulse triggering)
trigger point symbol switched off,
TVF
(TV signal, frame pulse triggering)
trigger point symbol switched off.
~
(line/mains triggering) trigger point symbol and
TRIG.
LEDs
(24)
switched off.
The readout displays
“TR:
~
”
. The
~
symbol can
be changed by 180° by using the trigger slope
function (
NM/AT - (16))
.
Please note:
In delay trigger mode (B time base) the instrument
is automatically set to DC trigger coupling. This set-
ting can not be changed with the TRIG. MODE push-
buttons.
In some trigger modes such as alternate triggering, some
trigger coupling modes are automatically disabled and
can not be selected.
This trigger mode is present if the trigger coupling information
in the trigger point symbol is inactive in line/main trigger
mode as there is no direct amplitude relationship between
the trigger voltage and the signal voltage.
(28) DEL.POS.
HO
–LED - Control knob with two functions and
associated LED.
The function of this control knob depends on the time
base mode.
HO
(hold off)
In A time base mode, the control knob applies to the
hold off time setting. If the
HO
-LED associated with the
knob is dark, the hold off time is set to minimum.
Turning the control knob clockwise switches the LED
on and extends the hold off time until the maximum is
reached (please note “Hold Off-time adjustment”). The
hold off time is automatically set to minimum (LED dark),
if the A time base setting is changed. The last hold off
time setting is stored if alternate (A and B) or B time
base mode is selected.
DEL.POS.
In
alternate
(A and B) and
B
time base modes, the knob
controls the delay time setting. Under alternate time
base mode conditions, the delay time is visible on the A
trace, beginning at the trace start and ending at the start
of the intensified sector. In the free run condition (delay
trigger not active) of the
B
time base, an approximate
value is displayed in the readout (
“Dt:...”
). This is an aid
to find the position of the intensified sector which may
be very small.
If only the
B
time base is being operated, the delay time
can be varied, but there is no intensified sector as the A
trace is not visible.
STORAGE MODE ONLY
The HOLD OFF function is not available in storage mode.
(29) TIME/DIV.
- Control knob with two functions.
The following description applies to the time base switch
function (
VAR
LED dark).
ANALOG MODE
Turning the control knob clockwise reduces the deflec-
tion coefficient in a 1-2-5 sequence and increases it if
turned in the opposite direction (ccw.). The time coef-
ficient(s) is (are) displayed in the readout.
In
A
time base mode, time deflection coefficients
between 500ms/div and 50ns/div can be chosen in 1-2-
5 sequence, if the X-MAG. x10 function is not activated.
During alternate
(A and B)
and
B
time base operation,
the control knob changes the B time base setting in 1-2-
5 sequence. The available deflection coefficient range
is from 20ms/div up to 50ns/div (without X-MAG. x10)
but the availability depends on the
A
time base setting.
The internal control of the oscilloscope prevents the
B
time deflection coefficient from becoming higher than
the
A
deflection coefficient, as such an operation
condition would make no sense. If the
A
time base
setting is 200µs/div the
B
time base range from 20ms/
div up to 500µs/div is not available and the maximum
time deflection coefficient for
B
would be 200µs/div. In
the last named condition the change of the
A
time base
from 200µs/div to 100µs/div switches the
B
time base
also to 100µs/div. However the
B
time base setting
remains unchanged if the
A
time base is set to 500µs/
div.
As already mentioned under
DUAL (23)
the channel
switching depends on the time deflection coefficient
setting. In the time base ranges from 500ms/div to
500µs/div chopped
(CHP)
channel switching is auto-
matically selected, through which the switching occurs
constantly during the time base sweeps. Alternate
(ALT)
channel switching is automatically used in all other time
deflection coefficient settings (200µs/div - 50ns/div). In
the latter case the active channel is switched off and
the previously inactive channel is switched on after the
completion of each time base sweep. To avoid inter-
ference in chopped mode, or to make both channels
appear simultaneously visible, the actual setting
(ALT
Controls and Readout
A
