Hitachi V-209 Operation Manual page 28

This means that CHI is used as the triggering signal when
investigating the length 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
selected 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
superimpose one on another.
Read the time difference between 50% amplitude points
of the two signals.
Sometimes the superimposing method is more convenient
from the point of view of procedure.
Time
difference Equalize
=>
"'
- ---- J
by V AR
( a ) Equal amplitude
measuring method
<CAUTIONS>
Since the pulsed wave contains many high-frequency wave
components (higher harmonics) depending on its width or
24
(b)
Suerposition
measuring method
period, pay the same attention as given to high frequency
signals when handling it. Accordingly, use a probe or coax­
ial cable and shorten the earth lead wire as much as possible.
Measurement rise (fall) time
(5)
of
To measure the rise time, pay attention not only to the
abovementioned items but also to measurement error.
The following equation is provided for the relation among
the rise time Trx of the wavefom1 to be measured, the rise
time Trs of oscilloscope, and the rise time Tro displayed on
the screen.
Tro Trx2 Trs2
+
When the rise time of the pulse going to be measured is
sufficiently longer than the rise time of the oscilloscope
(17.S ns in our case),the effect of the rise time of the oscil­
loscope on the measurement can be neglected. However, if
both are close to each other, measurement error may be
caused.
The true rise time is given by
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.