Hitachi V-355 Operation Manual page 24

This me ans that CH 1 is used as the triggering signal when
investigating the le ngth of time by which the signal of CH2
is delayed from the signal of CH 1 . CH2 is used in the
reversed case . In other words, the signal leading in phase is
sele cted as the triggering signal source .
If this process is reversed , the portion to be measured may
sometimes not appear on the screen. Thereafter , equalize
the amplitudes of the two signals appearing on the screen or
superimp ose one on another.
Read the time difference by the interval between 50% am­
plitude points of the two signals .
Some times the superimposing method is more conve nient
from the point of view of procedure .
0
difference Equalize
by VAR
- ---- J�
( a) Equal amplitude
measuring method
<CAUTIONS >
Since the pulsed wave contains many high-frequency wave
components (higher harmonics) depending on its width or
(b) Suerposition
measuring method
period, pay the same attention as give n to high frequency
signals when handling it . Accordingly, use a probe or coax­
ial cable and shorte n the earth lead wire as much as possible .
(5) Measurement of rise (fall) time
To measure the rise time pay attention not only to the
aboveme ntioned items but also to me asureme nt error.
The following relationship exists between the rise time Trx
of the waveform to be me asured, the rise time Trs of oscil­
loscope , and the rise time Tro displayed on the screen.
+
Trs2
Tro Trx2
When the rise time of the pulse going to be measured is
sufficiently lo nger than the rise time of the oscilloscope
(7ns in our case), the effect of the rise time of the oscil­
loscope on the me asurement can be neglected . However, if
both a re close to each other, measureme nt error may be
caused .
The true rise time i s give n b y
Trx Tro2 - Trs2
=
Moreover, in general, in a circuit free from waveform dis­
tortion such as overshoot and sag , the following relation­
ship is established between frequency band and rise time .
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