Philips PM3350A - Page 57

4-24
4 APPLICATIONS
In the following part the already mentioned time-base modes will be explained:
ROLL MODE
Lower frequency signals, such as reference voltage drift in an amplifier over
periods of several hours, car now be captured and stored in the memory. The
signal is built up point-by-point at the right-hand side of the screen and moves to
the left. The ROLL segment on the LCD indicates that the ROLL mode is
operative.
The ROLL mode is usually started with the release of the RESET knob, but is
also started when changing the triggering or amplitude control.
The TRIGGER DELAY defines the amount of the stored signal in the memory
before and after the trigger. As an example: In case a trigger delay of 0 is
selected, the ROLL mode stops when the startpoint of the acquisition has
reached the far left vertical graticule line (the extreme left of the CRT). Exactly
one screen Is filled this way. If a TRIGGER DELAY of -3 -s selected, the ROLL
mode stops when the startpoint of the acquisition has reached the fourth
graticule line (related to the left of the CRT).
The following TRIGGER MODE conditions can be applied, selectable with the TB
TRIG MODE button:
- AUTO
- TRIG
- SINGLE
- MULTI
The stop condition of the ROLL mode in auto trigger is not the
trigger level crossing point, but that point in time where tne
ROLL mode was first activated.
The stop condition is now defined by the actual trigger point, so
trigger source, trigger coupling, slope and level become valid.
After receiving the trigger pulse, the acquisition is then copied
to the display memory.
In this case the single shot acts identical to the TRIGger mode.
The principle of operation is a‘so identical to the TRIGger mode.
The first acquisition is copied to the selected register memory
(R1 or R2 or R3), the second acquisition is copied to the display
memory (RO), see also page 4-30. This mode is not selectable if
one of the PROCESS functions (ENVELOPE or AVERAGE) is
active (see page 4.40).
ATTENTION: Take note that the lower transition point oi the bandwidth for
TRiGger COUPLing P-P is limited to 20 Hz. So the peak-to-peak is
not applicable for the ROLL mode. The trigger coupling should be
set to DC.
4.2 USE AS A DIGITAL STORAGE OSCILLOSCOPE