Hioki ST4030, Instruction Manual

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Affects on Measurements According to the Length of the Test Lead
15.9 Affects on Measurements According to the
Length of the Test Lead
Even if measuring the same workpiece, the length of the test lead changes the waveform.
Following are waveforms with test lead lengths of 1.5 m, 3.0 m, and 5.0 m.
1.5 m
3.0 m
5.0 m
Using a longer test lead increases the cable capacity (C).
According to
T
=2 π √
LC, the longer the lead, the longer the oscillation period.
Because the cable’s parasitic inductance and parasitic capacitance increase with the length of the
test leads, the rising portion of the waveform is more likely to exhibit ringing.
Following are impulse response waveforms for the same workpiece (a coil of xx mH), measured
using 1.5 m test leads and 5.0 m test leads.
Voltage calibration is performed using the maximum voltage, including ringing. When extending the
standard 1.5 m test leads, arrange equipment so that the cables are as short as possible.
1.5 m cable
5.0 m cable