Gould 4070 - Page 9

Operation
Section 1
sample
illusory
image
Figure 1.1.6 Alias Generation
Operating Hints
The following list gives some of the more commonly met
problems in operating digital oscilloscopes, how to correct
them, and a brief explanation
of what was wrong.
You may need to consult later sections
of the manual as not
all
the operating features have been discussed so far.
Problem: No trace visible.
Trace intensity
too low
No stable trigger
Too much vertical shift
- Correct with Trace Intensity
Control.
Turn on other trace.
- Select Auto Trigger until
trace found.
- correct with
tht. \'ertical
Position
paddle.
Too much post storage shift- cancel post storage shift.
Input has large
DC offset - AC couple input signal.
- correct with position paddle.
- use a less sensitive range.
Problem: Trace not being acquired.
Trigger level incorrect - select AC coupling,
AUTO
Trigger source on the
wrong input
Trigger coupling on an
unsuitable setting
Hold on
Timebase on very slow
acquisition
and AC trigger, then adjust
the level control until the
trigger level 'bars' are lined up
with the centre
of the trace.
- change trigger source.
- change trigger coupling.
- release Hold.
- adjust timebase speed.
Insufficient
sjgnal to
trigger on
Instrument in single
capture mode
- use Auto Trigger.
- press Continuous.
Problem: Trace is unstable even when triggered.
Alias - check for alias with max-min
glitch detect and select a
faster timebase range.
Noisy input - select
DCLP or ACLP trigger
Trigger on
AUTO
Input non-repetitive
Input has many non-
identical trigger points
coupling.
- select bandwidth limit.
- adjust trigger level.
- With low frequency inputs,
below
40Hz, AUTO trigger
will
not work correctly.
Select Normal trigger.
- Select
NORM trigger mode
andS/Shot.
- use divide by N.
Problem: Trace has a very flat top or bottom.
Trace captured when in
limit and post storage
shift has been used.
- adjust pre-storage shift.
- use less sensitive range.
Problem: Trace is very 'dotty'.
Too much horizontal
expansion
- decrease expansion.
- use linear
or sine
interpolation.
- re-capture on a faster
timebase range.
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