Philips PM3320 Operating Manual page 131

VERTICAL
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4.41
4.4.2
PRINCIPLE OF OPERATION
In-this section, the principles of operation bre discussed at block diagram level, with special
emphasis being applied to those parts ofthe|circuit that differ from normal oscilloscope practice;
ie, the digital storage and control facilities.
GENERAL |
|
This digital storage oscilloscope comprises the following sections:
]
— asignal acquisition section which can be divided in a vertical section, a trigger section anda
conversion and processing section.
- a storage section H
- a display section |
— a control section |
- a front section }
- a power supply section
The signal acquisition section
Vertical section
The input signal(s) to be displayed can be applied to the BNC input sockets A (and) or B.
if the probe delivered with the oscilloscope is used, the attenuator setting of the oscilloscope is
adapted to the attenuator factor ofthe probe via the PROBE DETECTION contacts adjacent to the
BNC input connectors A and B.
The channels A and B are identical so only channel A is described.
The applied input signal is fed to the VERTICAL SIGNAL CONTROL via ATTENUATOR A.
In ATTENUATORA , the vertical sensitivity is determined, controlled by the AMPL/DIV button via
the CONTROL SECTION (indicated with C -->).
With the pushbutton COUPLING, a softkey menu is activated which makes selection of the
following functions possible:
- input coupling selection : AC-DC-GROUND
- input impedance selection: 1 MOhm -| 50 Ohm
- OFFSET selection (via preselected values)
The attenuation can be continuously aaa by the frontpanel VARIABLE contro! and when
active the UNCAL led will be on.
Vertical shift of the trace is determined in the VERTICAL SIGNAL CONTROL by the frontpane!
SHIFT control.
I
The pushbutton MODE makes via the softkeys selection of the following functions possible:
: invetsion of input signal - INVERT A (8)
— VERTICAL DISPLAY MODES
— BW UMIT
— MIN / MAX
:B
: bandwidth limiter
: minimum / maximum mode
tA; : only channel A
:A and B : channels A and B
: ADI : A and B added
¢ only channel B
The VERTICAL DISPLAY MODE is selected in the VERTICAL CHANNEL SWITCH which also
contains peak detectors to perform the softkey selectable MIN / MAX function.
The selected vertical input signal is then fed to the CONVERSION AND PROCESSING SECTION,