Hameg HM 1004-3 Series, Manual

Page: 17 / 36

17
Subject to change without notice
Controls and Readout
In A timebase mode, time deflection coefficients be-
tween 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 timebase operation, the
control knob changes the B timebase 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 timebase 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 timebase setting is 200µs/div the B timebase
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 timebase from 200µs/div to 100µs/div switches the B
timebase also to 100µs/div. However the B timebase
setting remains unchanged if the A timebase is set to
500µs/div.
As already mentioned under DUAL (18) the channel
switching depends on the time deflection coefficient
setting. In the timebase ranges from 500ms/div to 500µs/
div chopped (CHP) channel switching is automatically
selected, through which the switching occurs constantly
during the timebase 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 timebase sweep. To avoid interference in chopped
mode, or to make both channels appear simultaneously
visible, the actual setting (
ALT or CHP ) displayed in the
readout can be overwritten and changed to the opposite
mode. This is carried out by simultaneously pressing and
holding the
CHI (17) and the DUAL (18) pushbuttons.
(25)A/ALT - B - Pushbutton for timebase mode selection.
The instrument contains two timebases designated A
and B. With the aid of the B timebase, signal parts
displayed by the A timebase can be expanded in X-
direction. The expansion ratio depends on the time de-
flection coefficient ratio of both timebases (e.g. “A:
100µs”, “B:1µs” = 100). With higher expansion ratios the
B timebase trace intensity reduces.
Each time the A/ALT pushbutton is briefly pressed, the
timebase mode changes in the sequence A - alternate A
and B - A. The actual setting is displayed in the readout.
A:
In A timebase mode the TIME/DIV. (24) control knob is
operative only for this timebase. The readout then only
displays the A time coefficient. The timebase settings for
this condition are stored if the timebase mode is changed.
ALT:
If alternate (A and B = ALT) timebase mode is selected,
the
TIME/DIV (24) knob only controls the B timebase
switch or vernier function. The alternate timebase mode
is a subfunction of the B timebase mode where both
timebase traces are displayed. Consequently the readout
displays both time deflection coefficients (e.g. “A:100µs
B:1µs”). Unlike the former A timebase mode, an intensi-
fied sector is also visible on the A trace. This sector
indicates the signal part which is displayed by the B
timebase.
The intensified segment can be shifted horizontally by the
DEL. POS. (23) control knob continuously (if the B
timebase is operated in free run conditions). The differ-
ence between the start of the A timebase trace and the
beginning of the intensified sector shows the delay time.
This information is also displayed in the readout as an
approximative value (e.g. “
∆
t:2.5ms”) related on the
calibrated A time coefficient (uncalibrated e.g.
“
∆
t>2.5ms”). The width of the segment decreases when
the B time coefficient is set to a lower value (higher time
deflection speed).
For better reading, the vertical position of the B trace
position can be shifted (
please note “TRS” (8) ).
Alternate timebase mode causes the display to alter
between A and B timebase after each sweep. In alternate
DUAL mode the sequence is channel I with A timebase,
channel I with B timebase, channel II with A timebase and
channel II with B timebase.
B:
Pressing and holding this button switches over from A or
alternate timebase mode to B timebase mode. If B
timebase mode is selected, pressing and holding selects
alternate timebase mode. Briefly pressing this button
switches over from B timebase mode to A timebase
mode.
In B timebase mode the display of the A trace(s), the
intensified sector(s) and the A time coefficient display in
the readout are disabled. As the trace separation
(TR) is
no longer required under this circumstances, this func-
tion is switched off too. Consequently only the B time
coefficient is displayed by the readout.
If after switching on the B timebase (alternate or only B)
whether free run or triggered B operation is present
depends on the previous setting.
(26) DEL.TRIG. - VAR. - Pushbutton with two functions.
DEL. TRIG.:
Each time the pushbutton is briefly pressed, the instru-
ment switches between free run (untriggered) and trig-
gered B timebase, if alternate (A and B) or B timebase
mode is present.
The actual setting is displayed in the readout. Instead of
the approximate delay time (
“
∆∆∆∆∆
t:...” ) in free run mode,
the readout displays “
∆∆∆∆∆
Tr: slope, DC (trigger coupling)”