Hitachi V-209, Руководство по эксплуатации

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In general. tt tS safe to avoid measunng with non­
shielded connecting wire. When using a shieldmg wire,
connect one end of the shield to the earth terminal of
the oscilloscope and the other end to the grounding of
the circuit to be measured. It is deirable to use a coaxtal
cable with
B C
type connector.
The following cautions must be observed when per­
forming a wide band measurement. It ts necessary to
terminate with the characteristic impedance of the cable
when measuring a rapid nsing waveform or a high fre­
quency wave.
Especially when using a long cable. the absence of
a
terminating resistor will necessarily lead to a measure­
ment error derived from ringing phenomenon. Some
measunng circutls require a term mating reststor equal to
the charactensttc unpedance of the cable also on the
measurement terminal stde.
B C type terminating reststor (50 Q) ts conveniently
used for this purpose.
c In order to perform measurement with the measuring
circuit put in proper operating state, it is sometimes
necessary to terminate the cable with an impedance
which corresponds to the circuit to be measured.
o T h e stray capacity of the shield wire must be taken in 10
account when performing measurement with a long
shield wire. Since the shield wire normally in use has
a capacity of about I
00
pF per meter. its effect on the
circutt to be measured cannot be ignored. Use a probe to
minimize the cffection the circuit.
When the length of the shield wire is used or when the
length
of the non-terminated cable reaches I 4 wave
length or its multiples within the band of V-:!09 type
(I 4 wave length is about 3 meter when using a coaxial
cable at
}0 MHz),
oscillation may be caused near 5 mV
DIY range.
This is caused by the resonance between the externally
connected high-0 inductance and the input capacity
and can be avoided by reducing the Q.
Connect the cable or shield wire to the input connector
by way of a senally connected I
OOU
to
I n
reststor, or
perform measurement at other VOLT/DIY range.
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