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Keysight Technologies
Impedance Measurement Handbook
A guide to measurement technology and techniques
4th Edition
Application Note
i | Keysight | Impedance Measurement Handbook, A guide to measurement technology and techniques, 4th Edition - Application Note
Table of Contents
1.0
Impedance Measurement Basics
1.1 Impedance ........................................................................................................................ 1-01
1.2 Measuring impedance ..................................................................................................... 1-03
1.3 Parasitics: There are no pure R, C, and L components .................................................. 1-03
1.4 Ideal, real, and measured values ..................................................................................... 1-04
1.5 Component dependency factors ..................................................................................... 1-05
1.5.1 Frequency .............................................................................................................. 1-05
1.5.2 Test signal level ..................................................................................................... 1-07
1.5.3 DC bias................................................................................................................... 1-07
1.5.4 Temperature........................................................................................................... 1-08
1.5.5 Other dependency factors....................................................................................... 1-08
1.6 Equivalent circuit models of components........................................................................ 1-08
1.7 Measurement circuit modes ............................................................................................. 1-10
1.8 Three-element equivalent circuit and sophisticated component models ...................... 1-13
1.9 Reactance chart................................................................................................................ 1-15
2.0
Impedance Measurement Instruments
2.1 Measurement methods .................................................................................................... 2-01
2.2 Operating theory of practical instruments ...................................................................... 2-04
LF impedance measurement
2.3 Theory of auto balancing bridge method ....................................................................... 2-04
2.3.1 Signal source section ............................................................................................ 2-06
2.3.2 Auto-balancing bridge section ............................................................................. 2-07
2.3.3 Vector ratio detector section................................................................................. 2-08
2.4 Key measurement functions ............................................................................................ 2-09
2.4.1 Oscillator (OSC) level ............................................................................................ 2-09
2.4.2 DC bias .................................................................................................................. 2-10
2.4.3 Ranging function .................................................................................................. 2-11
2.4.4 Level monitor function .......................................................................................... 2-12
2.4.5 Measurement time and averaging ....................................................................... 2-12
2.4.6 Compensation function ........................................................................................ 2-13
2.4.7 Guarding ............................................................................................................... 2-14
2.4.8 Grounded device measurement capability .......................................................... 2-15
RF impedance measurement
2.5 Theory of RF I-V measurement method ......................................................................... 2-16
2.6 Difference between RF I-V and network analysis measurement methods ...................... 2-17
2.7 Key measurement functions ............................................................................................ 2-19
2.7.1 OSC level ............................................................................................................... 2-19
2.7.2 Test port ................................................................................................................ 2-19
2.7.3 Calibration ............................................................................................................ 2-20
2.7.4 Compensation ....................................................................................................... 2-20
2.7.5 Measurement range ............................................................................................. 2-20
2.7.6 DC bias .................................................................................................................. 2-20
ii | Keysight | Impedance Measurement Handbook, A guide to measurement technology and techniques, 4th Edition - Application Note
3.0
Fixturing and Cabling
LF impedance measurement
3.1 Terminal configuration ..................................................................................................... 3-01
3.1.1 Two-terminal configuration ................................................................................... 3-02
3.1.2 Three-terminal configuration ................................................................................ 3-02
3.1.3 Four-terminal configuration .................................................................................. 3-04
3.1.4 Five-terminal configuration ................................................................................... 3-05
3.1.5 Four-terminal pair configuration ........................................................................... 3-06
3.2 Test fixtures ...................................................................................................................... 3-07
3.2.1 Keysight-supplied test fixtures.............................................................................. 3-07
3.2.2 User-fabricated test fixtures.................................................................................. 3-08
3.2.3 User test fixture example....................................................................................... 3-09
3.3 Test cables ....................................................................................................................... 3-10
3.3.1 Keysight supplied test cables ............................................................................... 3-10
3.3.2 User fabricated test cables .................................................................................. 3-11
3.3.3 Test cable extension ............................................................................................. 3-11
3.4 Practical guarding techniques ........................................................................................ 3-15
3.4.1 Measurement error due to stray capacitances ..................................................... 3-15
3.4.2 Guarding techniques to remove stray capacitances ............................................ 3-16
RF impedance measurement
3.5 Terminal configuration in RF region ................................................................................ 3-16
3.6 RF test fixtures ................................................................................................................. 3-17
3.6.1 Keysight-supplied test fixtures ............................................................................. 3-18
3.7 Test port extension in RF region....................................................................................... 3-19
4.0 Measurement Error and Compensation
Basic concepts and LF impedance measurement
4.1 Measurement error .......................................................................................................... 4-01
4.2 Calibration ........................................................................................................................ 4-01
4.3 Compensation .................................................................................................................. 4-03
4.3.1 Offset compensation ............................................................................................ 4-03
4.3.2 Open and short compensations ........................................................................... 4-04
4.3.3 Open/short/load compensation .......................................................................... 4-06
4.3.4 What should be used as the load? ...................................................................... 4-07
4.3.5 Application limit for open, short, and load compensations ................................ 4-09
4.4 Measurement error caused by contact resistance ......................................................... 4-09
4.5 Measurement error induced by cable extension ............................................................ 4-11
4.5.1 Error induced by four-terminal pair (4TP) cable extension .................................. 4-11
4.5.2 Cable extension without termination .................................................................... 4-13
4.5.3 Cable extension with termination ......................................................................... 4-13
4.5.4 Error induced by shielded 2T or shielded 4T cable extension ............................. 4-13
4.6 Practical compensation examples .................................................................................. 4-14
4.6.1 Keysight test fixture (direct attachment type) ...................................................... 4-14
4.6.2 Keysight test cables and Keysight test fixture ...................................................... 4-14
4.6.3 Keysight test cables and user-fabricated test fixture (or scanner) ...................... 4-14
4.6.4 Non-Keysight test cable and user-fabricated test fixture .................................... 4-14
iii | Keysight | Impedance Measurement Handbook, A guide to measurement technology and techniques, 4th Edition - Application Note
RF impedance measurement
4.7
Calibration and compensation in RF region .................................................................. 4-16
4.7.1 Calibration ........................................................................................................... 4-16
4.7.2 Error source model .............................................................................................. 4-17
4.7.3 Compensation method ....................................................................................... 4-18
4.7.4 Precautions for open and short measurements in RF region ............................ 4-18
4.7.5 Consideration for short compensation ............................................................... 4-19
4.7.6 Calibrating load device ....................................................................................... 4-20
4.7.7 Electrical length compensation .......................................................................... 4-21
4.7.8 Practical compensation technique ..................................................................... 4-22
4.8
Measurement correlation and repeatability .................................................................. 4-22
4.8.1 Variance in residual parameter value ................................................................. 4-22
4.8.2 A difference in contact condition ........................................................................ 4-23
4.8.3 A difference in open/short compensation conditions ........................................ 4-24
4.8.4 Electromagnetic coupling with a conductor near the DUT ............................... 4-24
4.8.5 Variance in environmental temperature .............................................................. 4-25
5.0 Impedance Measurement Applications and Enhancements
5.1
Capacitor measurement ................................................................................................ 5-01
5.1.1 Parasitics of a capacitor ....................................................................................... 5-02
5.1.2 Measurement techniques for high/low capacitance .......................................... 5-04
5.1.3 Causes of negative D problem ............................................................................. 5-06
5.2
Inductor measurement ................................................................................................... 5-08
5.2.1 Parasitics of an inductor ...................................................................................... 5-08
5.2.2 Causes of measurement discrepancies for inductors ......................................... 5-10
5.3
Transformer measurement ............................................................................................. 5-14
5.3.1 Primary inductance (L1) and secondary inductance (L2) ................................... 5-14
5.3.2 Inter-winding capacitance (C) ............................................................................. 5-15
5.3.3 Mutual inductance (M) ......................................................................................... 5-15
5.3.4 Turns ratio (N)....................................................................................................... 5-16
5.4
5.5
5.6
5.7
5.8
5.9
Diode measurement ....................................................................................................... 5-18
MOS FET measurement ................................................................................................. 5-19
Silicon wafer C-V measurement .................................................................................... 5-20
High-frequency impedance measurement using the probe ......................................... 5-23
Resonator measurement ................................................................................................ 5-24
Cable measurements ..................................................................................................... 5-27
5.9.1 Balanced cable measurement ............................................................................. 5-28
5.10 Balanced device measurement ..................................................................................... 5-29
5.11 Battery measurement ..................................................................................................... 5-31
5.12 Test signal voltage enhancement .................................................................................. 5-32
5.13 DC bias voltage enhancement ...................................................................................... 5-34
5.13.1 External DC voltage bias protection in 4TP configuration ................................ 5-35
5.14 DC bias current enhancement ....................................................................................... 5-36
5.14.1 External current bias circuit in 4TP configuration ............................................. 5-37
5.15 Equivalent circuit analysis function and its application ................................................ 5-38
iv | Keysight | Impedance Measurement Handbook, A guide to measurement technology and techniques, 4th Edition - Application Note
Appendix A: The Concept of a Test Fixture’s Additional Error
.......
A.1 System configuration for impedance measurement ......................................................
A.2 Measurement system accuracy........................................................................................
A.2.1 Proportional error ..................................................................................................
A.2.2 Short offset error ...................................................................................................
A.2.3 Open offset error...................................................................................................
A.3 New market trends and the additional error for test fixtures ...........................................
A.3.1 New devices ...........................................................................................................
A.3.2 DUT connection configuration ..............................................................................
A.3.3 Test fixture’s adaptability for a particular measurement ......................................
A-01
A-01
A-01
A-02
A-02
A-03
A-03
A-03
A-04
A-05
B-01
C-01
D-01
E-01
Appendix B: Open and Short Compensation
.........................................
Appendix C: Open, Short, and Load Compensation
.............................
Appendix D: Electrical Length Compensation
.......................................
Appendix E: Q Measurement Accuracy Calculation
.............................

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