Philips PM2521 Operating Manual page 45

Selection of the trigger level
— Select the + or — trigger level by depressing pushbutton +/—.
Remark:
Signals which are higher or lower than the circuit zero of the PM 2521 (0 terminal) can be triggered with
respectively the + or — trigger level. In + trigger level mode the PM 2521 triggers on positive crossings of the
trigger level. In — trigger level mode the PM 2521 triggers on negative crossings of the trigger level.
TRIGGER POINTS (+ +) TRIGGER POINTS!--)
+ TRIGGER
LEVEL 0
rrm
_i
-TRIGGER
LEVEL
Fig. 16. Trigger leva! selection in function Hz.
ST 3015
820226
— Adjust the trigger level with the thumbwheel until the GATE indication on the display is ignited.
Remark:
The trigger level can be adjusted between zero and end of range.
The voltage reading on the display indicates the height of the trigger level.
If the input signal cannot be triggered, proceed as follows:
— Select another trigger level polarity by depressing pushbutton +/- and try to trigger again.
— Check whether the input signal is lower than 7,5 % of the end of range value of the selected trigger level
range. Signals lower than 7,5 % cannot be triggered accurately.
— Select a higher trigger level range by depressing pushbutton UP and try to trigger again.
Measurement of the frequency
— Select function Hz with the function selector.
The PM 2521 will now display the frequency of the input signal.
Remark:
The PM 2521 is switched to automatic ranging mode.
The available ranges in the Hz function are
RANGE
RANGING MODES GATE TIME
10 kHz MANUAL* only 10 s
100 kHz
AUTO or 1 s
1 MHz
MANUAL * 100 ms
10MHz 10 ms
Manual ranging mode can be selected by depressing pushbutton AUTO/MAN*.
By depressing either pushbutton UP or DOWN the ranges are selected.
If the measured value exceeds, the range end value (> 99999), overload (OL) will be displayed.
During measuring the GATE indication is ignited. This only means that the gate is open. It does not mean that
the PM 2521 triggers.
— If the display shows an unstable or a zero reading, check the sensitivity and the trigger level again.