Current Measurements And Capacitive Loads - Keithley 6430 Instruction Manual

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Current measurements and capacitive loads

When measuring current in a test circuit that has high capacitance, ringing may occur. Ring-

ing is the ﬂuctuation of current readings that is initiated by a voltage step. This ﬂuctuation

eventually decays to a settled current reading. The higher the capacitance, the more ringing that

Table 3-5 lists the maximum capacitive loads that the Model 6430 can accommodate effec-

tively. For the higher current ranges (1nA range and higher), the listed values represent the larg-

est capacitance in which ringing created by a voltage step will decay in less than one power line

cycle. For the lower current ranges (100pA and lower), the listed values represent the largest

capacitance that causes ringing that will settle in a reasonable amount of time.

Current measurements can be performed for higher capacitive loads as long as the increased

ringing can be tolerated. Ringing can be reduced by adding a resistor in a series with the load at

the expense of longer settling times. See Source capacitance in Appendix F for more

information .

Maximum capacitive loads

Current range

Capacitive Load

Basic Source-Measure Operation

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