Cable Compensation - Keithley 4200A-SCS Reference Manual

Appendix B: Using a Model 590 C-V Analyzer

Cable compensation

Signal pathways through the test cables, switch matrix, test fixture, and prober contribute unwanted
capacitances that may adversely affect the measurement.
To correct for these unwanted capacitances, you should do cable compensation before measuring
the capacitance of DUT. In general, you do cable compensation by connecting precisely known
capacitance sources in place of the DUT and then measuring them. The 590 then uses these
measured values to make corrections when measuring the DUT.
During cable compensation:
1. The 590 calculates the compensation parameters based on the comparison between the given
and measured values.
2. The 590 makes a probe-up offset measurement and suppresses any remaining offset
capacitance. This step is done every time a new measurement is made.
Typically, cable compensation is done for all measurement ranges (2 pF, 20 pF, 200 pF, and 2 nF) of
the 590. Once cable compensation is done, it does not have to be done again unless the connections
to the DUT are changed or power is cycled.
For each measurement range of the 590, you must use a low-capacitance source and a high-
capacitance source. The following table lists the Keithley Instruments Model 5909 capacitance
sources that can be used for each 590 range.
5909 capacitance sources
590 range
2 pF
20 pF
200 pF
2 nF
Cable compensation user modules
The 4200A-SCS KI590ulib user library includes the following user modules for cable
compensation:
•
SaveCableCompCaps590: Enter and save capacitance source values: The user enters the
actual capacitance values of the capacitance sources. When the test is executed, the
capacitance values are stored in a file at a user-specified directory path.
•
DisplayCableCompCaps590: Places capacitance values into the Analyze spreadsheet:
When this test is executed, the capacitance values saved by SaveCableCompCaps82 are
placed into the Analyze spreadsheet.
•
CableCompensate590: Performs cable compensation: The user specifies the ranges and test
frequencies for cable compensation. When this test is executed, on-screen prompts guide you
through the cable compensation process.
•
LoadCableCorrectionConstants: This function reads the cable compensation parameters for
the range and frequency specified from the cable compensation file and sends these parameters
to the 590.
Details on all user modules for the 590 are provided in
B-4
Low capacitance source
0.5 pF
4.7 pF
47 pF
470 pF
Model 4200A-SCS Parameter Analyzer Reference Manual
High capacitance source
1.5 pF
18 pF
180 pF
1.8 nF
KI590ulib user library
4200A-901-01 Rev. C / February 2017
(on page 6-312).