FUNCTION AND RANGE HINTS AND COMMENTS
The normal trigger level of the AC-coupled Input-A is
0 V. This is ideal for symmetrical signals like sine-
waves, since their average DC component is 50 % of
Vp-p.
Non-symmetrical signals however, might fail to trigger
if the trigger level is 0 V. Therefore there are three
trigger level settings available; one for small duty fac-
tors, one for symmetrical wave forms and one for
large duty factors.
It is often possible for the counter to trigger on
unsymmetrical signals even though the symmetrical
triggering is selected, provided that the sensitivity is
high enough. This however, gives poor noise
immunity.
If you don’t know the duty factor of the input signal,
select Auto. If that does not work (too low input
frequency) do as follows;
a) Set the sensitivity to max.
b) Select Trigger level .
c) Reduce the sensitivity until the gate indicator stops
blinking.
d) Check if trigger level or makes the gate
indicator start blinking again. If it does, leave the
trigger level in that position, otherwise return to trigger
level .
e) Turn the sensitivity down until the gate indicator
stops
blinking, then up slightly until it starts again. The
trigger
level is now correct.
When set to Auto the counter first tries the trigger
level for symmetrical signals. If that does not work, it
tries the other settings.
Auto does not work if TOT A is selected.
Range: Auto works with input frequencies from 100
Hz and up.
Use this setting if the duty factor is below 25 %.
A positive offset voltage is added to the trigger level.
Use this setting if the duty factor is between 25 %
and 75 %.
The trigger level is 0 V.
Use this setting if the duty factor is below 75 %.
A negative offset voltage is added to the trigger level.
Each digit that is blanked out is removed and re-
placed by a -. The numerical value on the display is
not rounded off. The blanking is cleared by reset,
changing settings or when all digits are blanked and
you press the BLANK DIGITS key once more.
This function is used to blank the display of irritating,
unstable digits.
OPERATING INSTRUCTIONS Page: 15
PM 6669 - OPERATORS MANUAL
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