Operating Instructions—Type 324
Loading.
Use a 10X probe whenever possible. It pro
vides more accurate waveform observation by reducing the
loading effect on the signal source. Deflection factors indi
cated by the VOLTS/DIV switch must be multiplied by 10
when a 10X probe is in use.
Phase and Polarity Relationships.
When internal trigger
ing is used, the signal slope displayed at the beginning of
the sweep is dependent upon the trigger slope selected by
the operator. If a comparison of phase or polarity is re
quired, use external triggering and the same trigger source
for the entire sequence of phase or polarity comparisons.
The examples in Fig. 2-13(B) use + internal triggering and
show the positive spike coincident with the rising portion
of the square wave. The examples given in Fig. 2-13(A)
both use the same + external trigger source and show that
the square wave actually goes negative at the time the posi
tive spike occurs.
External triggering is extremely useful in measuring
phase difference between signals. The circuit in Fig.
2-14(A) is used to demonstrate this feature.
(A ) Ground loop not completed.
(B) Ground loop completed.
Fig. 2-11. Ground loop effect.
Connect the reference waveform to the external trigger
ing and the vertical input connectors. Select negative slope
external triggering and adjust the triggering and horizontal
controls so that one cycle of the reference signal covers 9
divisions of horizontal trace, passing through 0° at the
intersection of the graticule center lines as in Fig. 2-14(B).
This causes each division of horizontal base line to display
40° of the waveform being applied.
Disconnect the reference waveform from the vertical in
put. Connect the shifted waveform to the vertical input
connector and measure the amount of separation between
the graticule center vertical line and the waveform 0° point
as in Fig. 2-14(C). Convert the amount of separation to
degrees, using the 40°/div value which was established pre
viously. If the 0° point has moved to the left, the waveform
leads the reference. If it has moved to the right, the wave
form lags the reference.
(A ) Ground loop completed through power supply common
ground.
(B) Probe ground lead connected to equipment ground.
Fig. 2-12. Reducing ringing caused by ground loop.
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2-19