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(6) Precautions on Direct Connection and Using a
Probe
Two different methods are available for applying
signals.
One is to connect a lead wire to the
input terminal of the oscilloscope directly,
and another is to use a probe.
When viewing a small signal in a circuit having
high signal source impedance, error may occur
in measurement due to the effect of parallel
capacity or induced noise in the input cable.
The following precautions should be observed
to avoid false readings.
Generally, with the
exception of a low-impedance circuit, the use
of a lead wire should be avoided.
If a lead wire other than the probe or shielded
wire is used, make the lead as short as pos
sible.
When using a shielded wire in a circuit
having high impedance, attention should be p'aid
to the loading effects of the sum of the input
capacitance of the oscilloscope and the dis
tributed capacitance of the probe or shielded
wire on the signal source.
The input terminal
of the oscilloscope has a capacitance of about
30pF in parallel with lMf2.
If the effect of
this parallel capacitance on the high impedance
signal source cannot be ignored, the use of the
low capacitance xlo probe is recommended.
(7) Low-capacitance probe
To avoid the ill effects by direct connection,
use a low-capacitance probe (xiO) whenever pos
sible.
When this probe is used, input impedance
is lOMH, 22pF, making it possible to reduce the
loading effects upon the signal source to a
great extent.
However, when the probe is used at xio, the
input signal is attenuated to 1/10.
This must
be taken into account in all measurements.
(8) Ground Connection
When using a probe, connect to a ground point
close to the signal source and use the probe
ground wire.
Triggering on waveforms
The most important factor in operating to lock
and display waveforms properly before measuring
them with the oscilloscope.
(9) How to provide synchronization
o Select the position of the SOURCE switch @
according to the connector where sync signal is
supplied.
Also select the position of the MODE
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