Philips pm2521 - Page 46

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6.4.1. JO. Time measurements (s)
GENERAL
The time measurements in the PM 2521 are made in conjunction with the trigger level function. Each time the
input signal exceeds the trigger level the PM 2521 is triggered. As the trigger level can be adjusted it is.
important to know where the trigger level is and if triggering takes place before time measurements are made.
*
The orfler for time measurement is as follows:
. — Selection of the sensitivity ranges
— Selection of the trigger ievel
— Time measurements
The time measurements function has two trigger modes viz.:
— Normal trigger mode
Signals which are higher or lower than the circuit zero of the PM 2521 (0 terminal) can be triggered with
the + or — trigger level respectively. In + trigger level mode the PM 2521 triggers on positive crossing of
the trigger level. In — trigger level mode the PM 2521 triggers on negative crossings of the trigger level.
TRIGGER POINTS (++) TRIGGER POINTS)--)
+TRIGGER i-
LEVEL o
ST 3015
820226
Fig. 17. Normal mode trigger level selection in function s.
— Special trigger mode with DATA HOLD PROBE PM 9263 (Start and stop on inversed slopes).
In data hold mode of the PM 9263 the PM 2521 triggers in + trigger level mode at a positive and negative
crossing of the trigger level. In — trigger level mode the PM 2521 triggers at a negative and a positive
crossing of the trigger level.
TRIGGER P0INTS(H—)
+TRIGGER
LEVEL 0
TRIGGER POINTS(- + )
-TRIGGER
LEVEL
ST 3016
820226
Fig. 18. Special mode trigger level selection in function s.
Remark:
The minimum width of a signal to measure time is 10 ms.