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PRINCIPLE OF OPERATION
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Each channel can be switched on/off with the ON key and bandwidth can be
limited to 20 MHz via BW LIMIT ’on’ in the VERT MENU.
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Trigger source selection for MTB and DTB is done via the keys TRIG1 ...
TRIG4 and the menu under the DTB key. PM3370B/80B/90B offer trigger
source selection via TRIG1, TRIG2 and EXT TRIG.
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The vertical signal position of each channel can be adjusted with a POS
control.
The FINAL VERTICAL AMPLIFIER drives the vertical deflection system of the
Cathode Ray Tube (CRT). The TRACE SEPARATION key pair adjusts the vertical
distance between MTB and DTB display, when in Alternate Timebase Mode.
2.4
HORIZONTAL DEFLECTION
The horizontal deflection consists of the blocks TRIGGERING, TIMEBASE and
FINAL VERTICAL AMPLIFIER. TRIGGERING and TIMEBASE are both split up
in sections for MTB and DTB; these sections are almost identical.
Triggering can be done via CH1 ... CH4 (PM3370B/80B/90B; CH1, CH2, EXT
TRIG) or a signal derived from the line voltage. The following controls adjust the
triggering:
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COUPLING permits selection between ac, dc, lf-reject, hf-reject and noise
suppression.
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SLOPE permits triggering on positive- or negative-going signal edges.
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LEVEL adjusts the signal level where the timebase is started.
The output of the TRIGGERING generates a pulse that starts the TIMEBASE.
The TIMEBASE generates a so-called sawtooth signal that gives a time linear
horizontal display on the CRT. The following controls influence the timebase:
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MTB/VAR and DTB adjust the horizontal time scale of MTB and DTB. The best
MTB time scale is selected automatically if AUTO RANGE is active.
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The TB MODE key permits selection between auto (free run), trig(gered) and
single (shot) mode of MTB. The SINGLE RESET key resets the MTB when in
single shot mode.
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The DTB key permits selection of the operating modes of the DTB.
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The HOLD OFF control adjusts the period of time that the MTB does not start
upon receipt of a trigger.
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The DELAY control adjusts the time delay between start of MTB and DTB.
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X POS controls the horizontal position of the signal display.