4.10 Applying the DC Bias Voltage
4-46 ZM2376
through the protection circuit of L
CUR
/L
POT
terminal, it is possible that the actual settling time can be
less than T
S
.
When the current enters the limited current range during charging/discharging, it will converges for
the settling time Tstl[s], which is determined by the output impedance Rd[] and capacitance C[F] of
DUT.
Tstl[s] 7.13×C×Rd .
Actions when there is a leak current or it takes time for charge/discharging
When the leak current is large due to a low insulation resistance of DUT, when the charging current
runs for a long time due to the dielectrics absorbing, or when charging takes a long time due to a
large capacitance, the measurement may be impossible by the following reasons:
• DC cancel becomes insufficient due to a leak current and output impedance to cause the voltage
sensing section to saturate.
• The peak value of the signal current exceeds the permissible range of measurement range.
• Auto selection of measurement range does not work properly.
Even in these situations, the measurement may be possible as follows.
Hold the measurement range to the range accepting measurement range.
Try changing the measurement range once.
However, it is afraid that the measurement accuracy may go down while exceeding the
recommended measurement range.
Increase the measurement signal level
Permissible range of the voltage and current measurement increases.
In the DC bias setting menu, select TRACK
Since DC cancel amount is adjusted following variation of the bias voltage actually applied to the
DUT, the voltage sensing section becomes less likely to saturate when measuring low impedance.
However, the current sensing section may saturate due to a leak current. When the current sensing
section saturates, adjust with the measurement range and measurement signal level as described
above.
ZM2376 fine adjusts the DC cancel amount at the voltage sensing section in the range of the DC bias
voltage ± 0.25V when the auto DC cancel function is enabled. However, it takes time to adjust. When
the auto DC cancel function is disabled, the cancel amount is equal to the set value of the bias
voltage.
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