Agilent Solutions for Measuring Permittivity and Permeability with
Contents
1. END M P Figure 30 Measurement procedure flowchart for the 16454A 3 4 6 Special considerations When measuring a magnetic mate rial with a high permittivity near 10 or above precise measurements cannot be performed near 1 GHz Permeability is derived from the inductance value of the combined impedance of the MUT and the fixture The measured impedance should be composed of inductance and a negligible amount of capaci tance When the magnetic material s permittivity is high current flows through the space between the MUT and the fixture This is equivalent to a capacitor connected in paral lel to the inductor of the MUT This parallel LC circuit causes an impedance resonance at a destined frequency The higher the permittiv ity the lower the resonant frequency will be and precise measurements will be difficult 3 4 7 Sample measurements Frequency characteristic measure ment results of a ferrite core are shown in Figure 31 The E4991B and the 16454A were used to obtain the results in Figure 31 4 Conclusion In this application note permittiv ity and permeability measurement methods using impedance measure ment technology were discussed The discussions covered various test fixtures structures applicable MUT sizes operation methods and special considerations By using this application note as a reference a measurement solution that satisfies measurement needs and2. Pa cres o SN me H viv p ij Zsm E4991B E4990A Ho h Cc b M Eie Zsm 2T p n m ER S Jopo hls Relative permeability Measured impedance with toroidal core Measured impedance without toroidal core Permeability of free space Height of MUT material under test Outer diameter of MUT Inner diameter of MUT Figure 27 Structure of the 16454A and measurement concept 3 4 4 Principal specifications Table 9 Principal specifications of the 16454A Frequency 1 kHz to 1 GHz Max dc bias current 500 mA Operating temperature 55 C to 150 C Terminal configuration 7mm Compensation Short Principal specifications of the 16454A are shown in Table 9 above Figures 28 and 29 show the mea surement accuracy when either the E4991B or the E4990A are used 3 4 5 Operation method Figure 30 displays the flowchart when using the 16454A for permeability measurements Each step of the flowchart is described here Step 1 Calibrate the measurement instrument When using the E4991B calibrate at the 7 mm terminal When using the E4990A perform SETUP on the 7 mm terminal of the 429424 Step 2 Connect the 16454A Connect the 16454A to the measurement instrument s 7 mm terminal When using the E4991B select the perme ability measurement mode Step 3 Compensate the residual impedance of the 16454A Insert only the MUT holder and perform short compensation St
3. c s 0 01 001 40 100 1k 10k 100 k 1M 10M 30M Frequency Hz Ns Figure 13 Loss tangent measurement accuracy supplemental data When using the 4285A or E4990A above 5 MHz it is necessary to perform load compensation in addition to open and short compensation For more details please refer to Section 2 4 5 Operation method 2 4 5 Operation method Figure 14 displays the flowchart when using the 16451B for permit tivity measurements Each step in the flowchart is described here Step 1 Prepare the dielectric material Fabricate the MUT to the appropriate size Use Figures 7 through 10 as references If the contacting electrode method with thin film electrodes is employed apply thin film electrodes to the surfaces of the MUT Step 2 Attach the guarded electrode Select the appropriate electrode and fit it into the 16451B Step 3 Connect the 16451B Connect the 16451B to the unknown termi nals of the measurement instrument Step 4 Cable length compensation Set the measurement instrument s cable length compensation function to 1 m Refer to the measurement instrument s operation manual for the setting procedure Step 5 Compensate the residual impedance of the 16451B Use the furnished attachment to perform open and short compensation at a specified frequency This is necessary before adjusting the guarded and unguarded electrodes to be parallel to each other Step 6 Adjust the electrodes To
4. Agilent o Solutions for Measuring Permittivity e09 9 and Permeability with LCR Meters and Impedance Analyzers CELL Se tuu eo tree Ce Cr tete CE ce pag CL 4m Ch em ae ae Gi Anticipate Accelerate Achieve ria Agilent Technologies Solutions for Measuring Permittivity and Permeability with LCR Meters and Impedance Analyzers Application Note 1369 1 1 Introductionz x ico liiibesbeiebenk daub PR Ge A Deb PR RISRERECRON Babb Reed E NR IE dae ra der 3 2 Petinittivity Evaluation ssi ree pex pe px Ru naa PENERE E crX god raeXciekRe x4 rre fos verveaqepPeurgdgpgu 4 2 1 Definition OF DekTlttlVItys esaet comae atts etra m caede Rea en O Run eal GSES asl Tee Me ankles hoe Rat ne oe 4 2 2 Parallel plate measurement method 0 n 5 2 3 Permittivity measurement system isiissssssssssssss esse ea n a 8 2 4 Measurement system using the 16451B dielectric test fixture issssssssssss eee eee eee e ees 8 2 5 Measurement system using the 16453A dielectric test fixture 0 eee eee eee ee eee eee e eee 13 3 Permeability Evaluation si 04 lt sseickeceies nag eta c eR Be See een eek dad Bhd bedded Babe cede SE M ELE CR 17 3 1 Definition of permeability ode tak Rer eR E RRPUPIS ORC PbirbrvueRbnetideiecerumRorrrcqusfeeped 17 3 2 Inductance measurement method oie ere me pe ER Ra Dea Seda PE ee GER Ere Bae TE REG EE Ed 17 3 3 Permeability measurement systeM 0 0 2 esa
5. enhance the measurement perfor mance a mechanism is provided to adjust the guarded and unguarded electrodes to be parallel to each other By performing this adjustment the occurrence of the airgap when using the contacting electrode method is minimized and an airgap with uniform thickness is created when using the non contacting electrode method The adjustment procedure is discussed in the operation manual of the 16451B Step 7 Set the measurement condi tions Measurement conditions such as frequency and test voltage level are set on the measurement instru ment Refer to the measurement instrument s operation manual for the setting procedure Step 8 Compensate the residual impedance of the 16451B Use the furnished attachment to perform open and short compensation of the measurement conditions set in Step 7 When using the Agilent 4285A or E4990A above 5 MHz it is necessary to perform load compensation also This is because for high frequency measurements it is difficult to disregard the residual impedance which cannot be removed by open and short compensation In order to compensate the frequency response of the 16451B a measured value at 100 kHz is used as a standard value and load compensation is performed at high frequencies The air capacitance formed by creating an airgap between the electrodes with nothing inserted is adopted as the load device for the 16451B Table 7 lists the recommended capacitance v
6. A was assembled properly measure the shorting plate at 1 MHz and check if the value falls within the prescribed range Perform this verification before short compensa tion For further details refer to the Operation Manual provided with the 16452A Step 5 Set the measurement conditions Measurement conditions such as frequency and test voltage level are set on the measurement instrument The measurement parameter should be set to Cp Rp Refer to the measurement instru ment s operation manual for the setting procedure Step 6 Perform short compensa tion Perform short compensation with the shorting plate inserted between the electrodes Step 7 Measure the air capacitance Remove the shorting plate and insert the appropriate spacer required for the sample liquid volume The air capacitance that exists between the electrodes is measured with the parameter Cp Rp Step 8 Pour liquid in Pour the liq uid into the inlet of the fixture Step 9 Measure liquid Perform a Cp Rp measurement with the liquid in the fixture Step 10 Calculate permittivity Permittivity and loss factor is calcu lated using the following equations L C m 1 MU uag Cp Equivalent parallel capacitance of MUT F Co Equivalent parallel capacitance of air F Rp Equivalent parallel resistance of MUT 0 o 2r f frequency Step 11 Drain liquid out Drain the liquid out from the outlet of the fixture A 1 6 Special conside
7. E4991B solves edge capacitance effect Open short and load compensation Direct readouts of complex permittivity are possible with the Option E4991B 002 material measurement software internal firmware in the E4991B Temperature characteristics measurements are possible from 55 C to 150 C with Options E4991B 002 and E4991B 007 For temperature response evaluation Option E4991B 007 temperature characteristic test kit is required A Microsoft Excel VBA sample program is pre installed in the E4991B that provides chamber control and measurement setup functions The sample program can be copied to an external PC OG ec Ct amp GG we cc cA 3 Eti Sa E im cc Applicable measurement instruments E4991B Option E4991B 002 2 5 2 Applicable MUT The applicable dielectric material is a solid sheet that is smooth and has equal thickness from one end to the other The applicable MUT size is shown in Figure 15 2 5 3 Structure The structure of the 16453A can be viewed in Figure 16 The upper elec trode has an internal spring which allows the MUT to be fastened between the electrodes Applied pressure can be adjusted as well The 16453A is not equipped with a guard electrode like the 16451B This is because a guard electrode at high frequency only causes greater residual impedance and poor fre quency characteristics To lessen the effect of edge capacitance a correction f
8. SO 9001 2008 Quality Management System Agilent Channel Partners www agilent com find channelpartners Get the best of both worlds Agilent s measurement expertise and product breadth combined with channel partner convenience www agilent com For more information on Agilent Technologies products applications or services please contact your local Agilent office The complete list is available at www agilent com find contactus Americas Canada 877 894 4414 Brazil 11 4197 3600 Mexico 01800 5064 800 United States 800 829 4444 Asia Pacific Australia 1 800 629 485 China 800 810 0189 Hong Kong 800 938 693 India 1800 112 929 Japan 0120 421 345 Korea 080 769 0800 Malaysia 1 800 888 848 Singapore 1 800 375 8100 Taiwan 0800 047 866 Other AP Countries 65 375 8100 Europe amp Middle East Belgium 32 0 2 404 93 40 Denmark 45 45 80 12 15 Finland 358 0 10 855 2100 France 0825 010 700 0 125 minute Germany 49 0 7031 464 6333 Ireland 1890 924 204 Israel 972 3 9288 504 544 Italy 39 02 92 60 8484 Netherlands 31 0 20 547 2111 Spain 34 91 631 3300 Sweden 0200 88 22 55 United Kingdom 44 0 118 927 6201 For other unlisted countries www agilent com find contactus BP 09 27 13 Product specifications and descriptions in this document subject to change without notice Agilent Technologies Inc 2013 2014 Published in USA May 28 2014 5980 2862EN ES Agilent Technologies
9. T The mea surement result will appear on the display The data can be analyzed using the marker functions 2 5 6 Special considerations As with the previous measurement system an airgap which is formed between the MUT and the electrodes can be a primary cause of measure ment error Thin materials and high k materials are most prone to this effect Materials with rough surfaces Figure 20 can be similarly affected by airgap Airgap Electrode Electrode M P Figure 20 Rough surfaced dielectric material There is a technique to apply a thin film electrode onto the surfaces of the dielectric material in order to eliminate the airgap that occurs between the MUT and the electrodes This technique is shown in Figure 21 and 22 An electrode the exact shape and size to fit the 16453A is fabricated onto the dielectric material using either high conductivity silver pastes or fired on silver The MUT should be shaped as in Figure 21 with the thin film electrode thinner than the dielectric material In this case it is vital to appropriately position the fabricated thin film electrode onto the MUT to precisely contact the electrodes of the 164534 Figure 22 Following this process will ensure a more accurate and reliable measurement In addition if the MUTs are very thin for example close to 100 um it is possible to stack 3 or 4 other MUTs and then make the measurement This
10. Table 5 Applicable MUT sizes for electrodes C and D Electrode type Material diameter Material thickness Electrode diameter C 56 mm t 10 mm 5 to 50 mm D 20 mm to 56 mm t lt 10 mm 5 to 14 mm ff C N The gap width shall be as small as practical Note signifies diameter Dimensions are in millimeters N 2 Figure 9 Electrode C dimensions Diameter of applied thin film electrodes on surfaces of dielectric material O71 Test material The gap width shall be as small as practical Note signifies diameter Dimensions are in millimeters Y Figure 10 Electrode D dimensions 2 4 3 Structure In order to eliminate the measurement error caused by edge capacitance a three terminal configuration includ ing a guard terminal is employed The structure of the 16451B is shown in Figure 11 The electrodes in the 16451B are made up of the following 1 Unguarded electrode which is connected to the measurement instrument s high terminal 2 Guarded electrode which is connected to the measurement instrument s low terminal 3 Guard electrode which is connected to the measurement instrument s guard terminal the outer conductor of the BNC connectors The guard electrode encompasses the guarded or main electrode and absorbs the electric field at the edge of the electrodes making accurate permittivity measurements possible 2 4 4 Pri
11. UT and without it Figure 6 Theoretically the electrode gap tg should be a little bit larger than the thickness of the MUT tm In other words the airgap tg tm should be extremely small when compared to the thickness of the MUT tm These requirements are necessary for the measurement to be performed appropriately Two capacitance measurements are necessary and the results are used to calculate permittivity The equation is shown at right Cs Capacitance without MUT inserted F Cs2 Capacitance with MUT inserted F Di Dissipation factor without MUT inserted D2 Dissipation factor with MUT inserted ty Gap between guarded guard electrode and unguarded electrode m tm Average thickness of MUT m Equations E j a i oa 1 x bm Cio t m t tan D x D D x G 1 when tan lt lt 1 Guarded electrode d g Guard electrode M Unguarded electrode Figure 6 Non contacting electrode method Table 3 Comparison of parallel plate measurement methods Method Contacting electrode Non contacting electrode Contacting electrode without thin film electrode with thin film electrode Accuracy LOW MEDIUM HIGH Application MUT Solid material with a flat and Solid material with a flat and Thin film electrode must be smooth surf
12. ace smooth surface applied onto surfaces Operation 1 measurement 2 measurements 1 measurement 2 3 Permittivity measurement system Two measurement systems that employ the parallel plate method will be discussed here The first is the 16451B dielectric test fixture which has capabilities to measure solid materials up to 30 MHz The latter is the 16453A dielectric mate rial test fixture which has capabili ties to measure solid materials up to 1 GHz Details of measurement systems described in this note will follow the subheadings outlined below 1 Main advantages 2 Applicable MUT 3 Structure 4 Principal specifications 5 Operation method 6 Special considerations 7 Sample measurements 2 4 Measurement system using the 16451B dielectric test fixture 2 4 1 Main advantages Precise measurements are possible in the frequency range up to 30 MHz Four electrodes A to D are provided to accommodate the contacting and non contacting electrode methods and various MUT sizes Guard electrode to eliminate the effect of edge capacitance Attachment simplifies open and short compensation Can be used with any impedance measuring instrument with a 4 terminal pair configuration Applicable measurement instruments E4990A 4285A E4980A and E4981A 2 4 2 Applicable MUT The applicable dielectric material is a solid sheet that is smooth and has equal thickness from one end to the other The applicable
13. alues that are obtained by adjusting the height of the air gap between the electrodes It is assumed that the air capacitance has no frequency dependency no loss and has a flat response The capacitance value Cp at 100 kHz G is assumed to be zero is used for load compensation Step 9 Insert MUT Insert the MUT between the electrodes Step 10 Cp D measurement The capacitance Cp and dissipation fac tor D is measured When employing the non contacting electrode method two Cp D measurements are per formed with and without the MUT Step 11 Calculate permittivity As previously discussed in Section 2 2 use the appropriate equation to calculate permittivity START M P N 1 Prepare the dielectric material 2 Attach the guarded electrode J 3 Connect the 16451B J 4 Cable length compensation J 5 Compensation for adjustment of electrodes J 6 Adjust the electrodes 7 Set the measurement conditions J 8 Compensate the residual impedance Tie A J 9 Insert the MUT J 10 Cp D measurement J 11 Calculate permittivity J END Ns A Figure 14 Measurement procedure flowchart for the 16451B Table 7 Load values Electrode Recommended capacitance A 50 pF 0 5 pF B 5 pF 0 05 pF C D 1 5 pF 0 05 pF Measured Cp value at 100 kHz 2 4 6 Special considerations As m
14. asure vector components of capacitance C and dissipation D and a software program would calculate permittivity and loss tangent The flow of the electrical field in an actual measurement is shown in Figure 3 When simply measuring the dielectric material between two electrodes stray capacitance or edge capacitance is formed on the edges of the electrodes and consequently the measured capacitance is larger than the capacitance of the dielectric material The edge capacitance causes a measurement error since the current flows through the dielec tric material and edge capacitor A solution to the measurement error caused by edge capacitance is to use the guard electrode The guard electrode absorbs the electric field at the edge and the capacitance that is measured between the electrodes is only composed of the current that flows through the dielectric material Therefore accurate measurements are possible When the main elec trode is used with a guard electrode the main electrode is called the guarded electrode r Electrodes Area A Equivalent ro ia Solid thickness t Liquid Figure 2 Parallel plate method Y G jwCp e e e Co Air capacitance _ Cp 6G amp j 3 Co t Cp A g t g icu Edge capacitance stray Guard electrodes Electrical field Electrical field Figure 3 Effect of guard electrode Contacting electrod
15. asurement error is determined by the equation shown in Figure 5 Measurement error is a function of the relative permittivity er of the MUT thickness of the MUT tm and the airgap s thickness ta Sample results of measurement error have been calculated in Table 2 Notice that the effect is greater with thin materials and high x materials tm A Cy Ex g T Capacitance of dielectric material m A z T Capacitance of airgap a Measured capacitance Cor 1 1 Ser Eo te _ C C Measured error 1 fen 2 amp 1 due to airgap e Figure 5 Airgap effects Table 2 Measurement error caused by airgap Ne 2 5 10 20 50 100 t t 1 Kil 0 4 0 1 0 0 5 0 0 0 005 0 5 2 4 9 20 33 0 01 1 4 8 16 33 50 0 05 5 16 30 48 7096 8396 0 1 896 2196 4596 6396 8296 90 This airgap effect can be eliminated by applying thin film electrodes to the surfaces of the dielectric material An extra step is required for material preparation fabricating a thin film electrode but the most accurate measurements can be performed Non contacting electrode method This method was conceptualized to incorporate the advantages and exclude the disadvantages of the contacting electrode method It does not require thin film electrodes but still solves the airgap effect Permittivity is derived by using the results of two capacitance measure ments obtained with the M
16. conditions can be selected easily 20 ur 20 00 Ref 60 00 10 00 Ref 30 00 rq 160 0 1 25 958762 MHz 131 12 1 25 958762 MHz 24 287 140 0 120 0 100 0 80 00 60 00 40 00 20 00 0 000 20 00 40 00 x 1 Stare 1 MHz 0SC 100 mV stop 1 GHz SSH STEM Figure 31 Frequency response of ferrite core p 120 Appendix A Permittivity Evaluation of Liquids Permittivity measurements are often used for evaluation of liquid characteristics Permittivity mea surements do not change the liquid physically and can be conducted rather simply and quickly As a result they are utilized in a wide array of research areas Here the 16452A liquid test fixture which employs the parallel plate method will be discussed as a permittivity measurement system for liquids A 1 Measurement system using the 16452A liquid test fixture A 1 1 Main advantages Wide frequency range from 20 Hz to 30 MHz Plastic resins oil based chemical products and more can be measured Measurement is possible with a small volume of test liquid so MUT is not wasted Temperature characteristic measurements are possible from 20 C to 125 C Can be used with any impedance measuring instrument that has a 4 terminal configuration A 1 2 Applicable MUT The sample liquid capacity is depen dent upon which spacer is used The spacer adjusts the gap between the electrodes and causes the air capaci ta
17. dielectric material s size is determined by the measurement method and type of electrode to be used Electrodes A and B are used for the contact ing electrode method without the fabrication of thin film electrodes Electrodes C and D are used for the contacting electrode method with the fabrication of thin film electrodes When employing the non contacting electrode method electrodes A and B are used In this method it is recommended to process the dielectric material to a thickness of a few millimeters The difference between electrodes A and B is the diameter the same difference applies to electrodes C and D Electrodes A and C are adapted for large MUT sizes and electrodes B and D are adapted for smaller MUT sizes The applicable MUT sizes for each electrode are shown in Tables 4 and 5 The dimensions of each electrode are shown in Figures 7 through 10 Table 4 Applicable MUT sizes for electrodes A and B Electrode type Material diameter Material thickness Electrode diameter A 40 mm to 56 mm t 10 mm 38 mm B 10 mm to 56 mm t 10 mm 5 mm C b Electrode A Test material 40 to 56 Note signifies diameter Dimensions are in millimeters A Figure 7 Electrode A dimensions L JJ Electrode B Test material Note signifies diameter Dimensions are in millimeters Mu Figure 8 Electrode B dimensions
18. e measurement conditions 4 Connect the 16453A D Y 5 Input thickness of load device v G A 6 Calibrate the measurement plane J Y 7 Insert the MUT D Y 8 Measure the MUT END M Figure 19 Measurement procedure flowchart for the 16453A Frequency Mz Figure 17 Permittivity measurement accuracy supplemental data tiin 2 Tr80 5 tan 6 error 0001 1000k 10M Frequency Hz er m 10 Figure 18 Loss tangent measurement accuracy supplemental data Step 1 Select the measurement mode Select permittivity measure ment in E4991B s utility menu Step 2 Input the thickness of MUT Enter the thickness of the MUT into the E4991B Use a micrometer to measure the thickness Step 3 Set the measurement condi tions of the E4991B Measurement conditions such as frequency test voltage level and measurement parameter are set on the measurement instrument Step 4 Connect the 16453A Connect the 16453A to the 7 mm terminal of the E4991B Step 5 Input the thickness of load device Before compensation enter the furnished load device s PTFE board thickness into the E4991B Step 6 Calibrate the measurement plane Perform open short and load calibration Step 7 Insert MUT Insert the MUT between the electrodes Step 8 Measure the MU
19. e method This method derives permittivity by measuring the capacitance of the electrodes contacting the MUT directly see Figure 4 Permittivity and loss tangent are calculated using the equations below Cp Equivalent parallel capacitance of MUT F D Dissipation factor measured value tm Average thickness of MUT m A Guarded electrode s surface area m d Guarded electrode s diameter m y Permittivity of free space 8 854 x 10 F m Equations tm XC E bm X C T Axe 2 E 2 tan D The contacting electrode method requires no material preparation and the operation involved when measuring is simple Therefore it is the most widely used method However a significant measure ment error can occur if airgap and its effects are not considered when using this method When contacting the MUT directly with the electrodes an airgap is formed between the MUT and the electrodes No matter how flat and parallel both sides of the MUT are fabricated an airgap will still form Guarded electrode E S Hi M Guard electrode MUT Unguarded electrode Figure 4 Contacting electrode method This airgap is the cause for measure ment error because the measured capacitance will be the series connection of the capacitance of the dielectric material and the airgap The relationship between the airgap s thickness and me
20. entioned before to reduce the effect of the airgap which occurs between the MUT and the electrodes it is practical to employ the contacting electrode method with thin film electrodes Refer to Section 2 2 Electrodes C and D are provided with the 16451B to carry out this method Materials under test that transform under applied pressure cannot keep a fixed thickness This type of MUT is not suitable for the contacting electrode method Instead the non contacting method should be employed When the non contacting method is employed the electrode gap tg is required to be at most 10 larger than the thickness of the MUT It is extremely difficult to create a 10 electrode gap with thin film materials Therefore it is recommended that only materials thicker than a few millimeters be used with this method The micrometer on the 16451B is designed to make a precise gap when using the non contacting electrode method Accurate measurements of the thickness of MUT cannot be made when employing the contacting elec trode method This is because the micrometer scale is very dependent upon the guard and the unguarded electrodes being parallel Using a separate micrometer for measuring thickness is recommended 2 5 Measurement system using the 16453A dielectric material test fixture 2 5 1 Main advantages Wide frequency range from 1 MHz 1 GHz Option E4991B 002 material measurement software internal firmware in the
21. ep 4 Input size of MUT Enter the size of the MUT into the measurement instrument s menu Use a micrometer to measure the size Step 5 Insert MUT Insert the MUT with the holder into the 16454A Step 6 Set the measurement condi tions Measurement conditions such as frequency test signal level and measurement parameter are set on the measurement instrument C 5 hin 10 mm 3000 2500 2000 5 2500 1000 sok 20 0 1k 10k 100k 1M 10M 10M 1G Frequency Hz V J Figure 28 Permeability measurement accuracy supplemental data gt h In 10 mm 1 00 E 01 1 00 E 00 areo LAO 00 E 00 fs lio tan error Ea 00 E 00 E Ios 00 E 00 1k M 10k 100k 1M Frequency Hz 10M 100M 1G Figure 29 Loss tangent measurement accuracy supplemental data Step 7 Measure the MUT The measurement result will appear on the display The data can be analyzed using the marker functions Internal firmware comes standard with the material measurement func tion when using the E4991B Option E4991B 002 For more details refer to the Operation Manual of the E4991B f HN START i i 1 Calibrate the instrument T 2 Connect the 16454A Y a E N 3 Compensate the residual impedance Y 4 Input the size of the MUT Y 5 Insert the MUT Y C 6 Set the measurement conditions J Y 7 Measure the MUT
22. eraction of a material with a magnetic field It is the ratio of induction B to the applied magnetizing field H Complex relative permeability ur consists of the real part ur that represents the energy storage term and the imaginary part ur that represents the power dissipation term It is also the complex permeability u relative to the permeability of free space uo as shown in Figure 24 The inefficiency of magnetic material is expressed using the loss tangent tan 6 The tan 6 is the ratio of j to jr The term complex relative permeability is simply called per meability in technical literature In this application note the term permeability will be used to refer to complex relative permeability 3 2 Inductance measurement method Relative permeability of magnetic material derived from the self induc tance of a cored inductor that has a closed loop such as the toroidal core is often called effective permeability The conventional method of measur ing effective permeability is to wind some wire around the core and evaluate the inductance with respect to the ends of the wire This type of measurement is usually performed with an impedance measuring instrument Effective permeability is derived from the inductance mea surement result using the following equations 7 Leg uo N A 5o IR Ri 1 us N oA u _ Hr 7 Mp ju real part B Ww H tan B g
23. l test fixture 3 4 1 Main advantages Wide frequency range from 1 kHz to 1 GHz Simple measurements without needing a wire wound around the toroid Two fixture assemblies are provided for different MUT sizes Direct readouts of complex permeability are possible with the E4991B Option E4991B 002 material measurement software or with the E4990A For temperature response evaluation Option E4991B 007 temperature characteristic test kit is required A Microsoft Excel VBA sample program is pre installed in the E4991B that provides chamber control and measurement setup functions The sample program can be copied to an external PC The E4990A does not have a high temperature test head i 2 Applicable instruments E4991B Option E4991B 002 E4990A and 42942A Temperature characteristic measurements are possible from 55 C to 150 C with the E4991B Options E4991B 002 and E4991B 007 3 4 2 Applicable MUT The applicable magnetic material can only be a toroidal core The applicable MUT size is shown in Figure 26 3 4 3 Structure The structure of the 16454A and the measurement concept are shown in Figure 27 When a toroidal core is inserted into the 164544 an ideal 85mm Small size Large size M Figure 26 Applicable MUT size single turn inductor with no flux leakage is formed Permeability is derived from the inductance of the toroidal core with the fixture
24. lly used to express the relative lossiness of a material The term dielectric constant is often called permittivity in technical literature In this application note the term permittivity will be used to refer to dielectric constant and complex relative permittivity K 2zg E Real part XN r Ee X Imaginary part tan T Real tan D Dissibation factor K Dielectic constant i Complex relative permitivity Permitivity of 1 9 free a X 10 F m g j c Eo Eo Imaginary r 36x Figure 1 Definition of relative complex permittivity zr 2 2 Parallel plate measurement method of measuring permittivity When using an impedance measuring instrument to measure permittivity the parallel plate method is usually employed An overview of the parallel plate method is shown in Figure 2 The parallel plate method also called the three terminal method in ASTM D150 involves sandwiching a thin sheet of material or liquid between two electrodes to form a capacitor Note Throughout the remainder of this document materials under test whether the material is a solid or a liquid will be referred to as MUT The measured capacitance is then used to calculate permittivity In an actual test setup two electrodes are configured with a test fixture sandwiching dielectric material The impedance measuring instrument would me
25. lutions for measuring permittivity and permeability Agilent literature number 5965 9430E Application Note 380 1 Dielectric constant measurement of solid materials using the 16451B dielectric test fixture Agilent literature number 5950 2390 Accessories Selection Guide for Impedance Measurements Agilent literature number 5965 4792E Agilent 16451B Operation and Service Manual PN 16451 90020 Agilent 16452A Operation and Service Manual PN 16452 90000 Agilent 16454A Operation and Service Manual PN 16454 90020 Web resources Please visit our website at www agilent com find impedance for more information about impedance test solutions www agilent com find Icrmeters for more information about Icr meters For more information about material analysis visit www agilent com find materials e LXI WARRANTY myAgilent www agilent com find myagilent A personalized view into the information most relevant to you www lxistandard org LAN eXtensions for Instruments puts the power of Ethernet and the Web inside your test systems Agilent is a founding member of the LXI consortium Three Year Warranty www agilentcom find ThreeYearWarranty Beyond product specification changing the ownership experience Agilent is the only test and measurement company that offers three year warranty on all instruments worldwide www agilent com quality Agilent Electronic Measurement Group DEKRA Certified I
26. mittivity and permeability parameters Measurement parameter Measurement technology Measurement method Impedance analysis Parallel plate Network analysis Reflection wave Permittivity S parameters Cavity Free space Impedance analysis Inductance Permeability Network analysis Reflection wave S parameters Cavity 2 Permittivity Evaluation 2 1 Definition of permittivity Permittivity describes the interaction of a material with an electric field The principal equations are shown in Figure 1 Dielectric constant x is equivalent to the complex relative permittivity er or the complex permittivity relative to the permittivity of free space 9 The real part of complex relative permit tivity er is a measure of how much energy from an external field is stored in a material gr gt 1 for most solids and liquids The imaginary part of complex relative permittivity Cer is called the loss factor and is a measure of how dissipative or lossy a material is to an external field sr is always gt 0 and is usually much smaller than The loss factor includes the effects of both dielectric loss and conductivity When complex permittivity is drawn as a simple vector diagram as shown in Figure 1 the real and imaginary components are 90 out of phase The vector sum forms an angle with the real axis er The tangent of this angle tan 6 or loss tangent is usua
27. n 18 3 4 Measurement system using the 16454A magnetic material test fixture 18 4 IARE 20 Un qM IL 21 A Permittivity Evaluation of Liquids iisissiiessssssse he 21 A 1 Measurement system using the 16452A liquid test fixture sssssssssssss IRR 21 ATA Main advantages ssi is dber x ee ror etie ep akna r i EN TEE ped wa ganes REA te Pek een anges dated dass 21 Wine m 21 ANS Struc sooo edo vender eee Id ORE RS ERAN S UR RENNES Au S Abas aes e dd en ws 21 ATA Principal specrfiCatloris us sachets enddhed beau Mises tibia wisi angi etin awh bbe eat oo See RISO 22 A 1 5 Operation method ssc nbn RR aa tine bec peREDRRPURERPUERRRMERDRU REEF ak ecdons deme eee DNE PEU RS 23 A 1 6 Special considerations 0 0c mrina esas hn hh hh ka en nee teense ten m rea 23 References oere noci DIRE e dea whee heb bes dd oi dae eb a ds ead denen bee eh ep eh eee 2 Pa bead ERES 24 1 Introduction Recently electronic equipment technology has dramatically evolved to the point where an electronic component s material characteristics becomes a key factor in a circuit s behavior For example in the manu facture of high capacitance multi layer ceramic capacitors MLCCs which are being used more in digital media appliances employing high K dielectric constant material is required In addition various elect
28. nce to be altered as well Table 10 lists the available spacers and the corresponding sample liquid capacities A 1 3 Structure The structure of the 16452A is shown in Figure 32 Three liquid inlets simplify pouring and draining and the fixture can be easily disas sembled so that the electrodes can Applicable instruments E4990A and E4980A Table 10 Relationship between spacers and liquid capacity Sample liquid capacity 3 4 ml 3 8 ml 4 8 ml 6 8 ml Air capacitance no liquid present 34 9 pF 21 2 pF 10 9 pF 5 5 pF 25 15 10 10 Spacer thickness 1 3 mm 1 5 mm 2mm 3mm Figure 32 Structure of the 16452A A 1 m cable is required for connect ing to the measurement instrument Appropriate cables are listed in Table 11 Table 11 1 m cables for the 16452A Temperature Part number 0 C to 55 C 16048A 20 C to 125 C 16452 61601 20 C to 125 C 16048G E4990A only 21 A 1 4 Principal specifications Table 12 Principal specifications of the 16452A Frequency 20 Hz to 30 MHz Max voltage t42V Operating temperatures 20 C to 125 C Terminal configuration 4 terminal pair SMA Compensation Short The principal specifications of the 16452A are shown in Table 12 and the measurement error is calculated using the following equation Measurement accuracy A B C Error A see Table 13 Error B when gr 1 see Figure 33 Error C err
29. ncipal specifications Table 6 Principal specifications of the 16451B Guard terminal Unguarded electrode Hcur Frequency lt 30 MHz Max voltage 42 V Operation temperature 0 C to 55 C Terminal configuration 4 terminal pair BNC Cable length 1m Compensation Open short The principal specifications are shown in Table 6 Figures 12 and 13 show the measurement accuracy when Agilent s E4990A is used Further details about the measurement accuracy can be obtained from the Accessories Selection Guide for Impedance Measurements literature number 5965 4792E a Hpot 4 terminal ae Lput pair Lcur M E Figure 11 Structure of the 16451B Electrode A t2 1 mm 50 45 af X 35 w 30 er 50 25 LMS 1 010 A A A ee er 20 p 20 manitis er 10 9 ap PEro dare 0 77 er 5 lt n e er 2 10 prr Eee Ele eee edet 5 E HITM EHE BB HER m Hnc ever 0 shit Eee ere BN ee ee g 40 100 1k 10 100 k 1M 10M 30M Frequency Hz V P Figure 12 Permittivity measurement accuracy supplemental data 4 Y i Electrode A t 1 mm 1 a S o 01
30. or of measurement instrument Table 13 Error A Spacer thickness mm B 1 3 0 005 x MRP 1 5 0 006 x MRP 2 0 0 008 x MRP 3 0 0 020 x MRP M R P is measurement relative permittivity 22 Error B 10 0 1 0 0 1 20 25 0 2 0 15 500k 2M 5M 15M 20M 10k 100k 1M 10M 30M Frequency Hz Figure 33 Relative measurement accuracy supplemental data A 1 5 Operation method Figure 34 displays the flowchart when using the 16452A for permittivity measurements of liquids Each step of the flowchart is described here Step 1 Assemble the 16452A and insert the shorting plate While attaching the high and low elec trodes insert the shorting plate between them Next prepare the 16452A for measurement by con necting the SMA BNC adapters to the terminals of the fixture and putting the lid on the liquid outlet Step 2 Connect the 16452A to the measurement instrument Select the appropriate 1 m cable depending on the operating temperature and the measurement instrument Connect the 16452A to the UNKNOWN ter minals of the measurement instru ment Step 3 Compensate the cable length Set the measurement instrument s cable length compensation function to 1 m Refer to the measurement instrument s operation manual for the setting procedure Step 4 Check the short residual of the 16452A To verify whether the 16452
31. rations There is a high possibility that liquids with bulk conductivity such as salt Na Cl or ionic solutions cannot be measured This is due to the electrode polarization phenomenon which causes incorrect capacitance measurements to occur for these types of liquids Even for low frequency measurements of liquids that do not have bulk conductivity such as water there is a high possi bility that electrode polarization will occur START v 1 Assemble the 16452A and insert the shorting plate Y 2 Connect the 16452A d 3 Cable length compensation Y 4 Check the short residual 5 Set the measurement conditions J Y 6 Perform short compensation Y 7 Measure the air capacitance a 8 Pour the liquid in T 9 Measure the liquid Y 10 Calculate permittivity k 11 Drain the liquid am zz ac END M T Figure 34 Measurement procedure flowchart for the 16452A 23 References 24 ASTM Test methods for A C loss characteristics and permittivity dielectric constant of solid electrical insulating materials ASTM Standard D 150 American Society for Testing and Materials ASTM Test methods for D C resistance or conductance of insulating materials ASTM Standard D 257 American Society for Testing and Materials Application Note 1297 So
32. rical performance evaluations such as frequency and temperature response must be performed before the materials are selected In fields outside of electronic equipment evaluating the electrical characteristics of materials has become increasingly popular This is because composition and chemical variations of materials such as solids and liquids can adopt electrical char acteristic responses as substituting performance parameters A material evaluation measurement system is comprised of three main pieces These elements include precise measurement instruments test fixtures that hold the material under test and software that can calculate and display basic material parameters such as permittivity and permeability Various measurement methods for permittivity and perme ability currently exist see Table 1 However this note s primary focus will be on methods that employ impedance measurement technology which have the following advantages Wide frequency range from 20 Hz to 1 GHz High measurement accuracy Simple preparations fabrication of material measurement setup for measurement This note begins by describing measurement methods systems and solutions for permittivity in Section 2 followed by permeability in Section 3 The resistivity measure ment system and the permittivity measurement system for liquids are described later in the appendix Table 1 Measurement technology and methods for per
33. t W i uo e imaginary part Up imaginary faa Ur real Complex relative permeability Permeability of free space 4x X 107 H m Figure 24 Definition of complex permeability m Rer Equivalent resistance of magnetic core loss including wire resistance Lef Inductance of toroidal coil Rw Resistance of wire only Lw Inductance of air core coil inductance N Turns Average magnetic path length of toroidal core m A Cross sectional area of toroidal core m O 2r f frequency Lp 4n x 107 H m Equivalent circuit Depending on the applied magnetic field and where the measurement is located on the hysteresis curve permeability can be classified in degree categories such as initial or maximum Initial permeability is the most commonly used parameter among manufacturers because most industrial applications involving magnetic material use low power levels This application note focuses on effective permeability and initial permeability derived from the inductance measurement method Figure 25 Method of measuring effective permeability Some manufacturers use initial permeability even for magnetic materials that are employed at high power levels 3 3 Permeability measurement system The next section demonstrates a permeability measurement system using the 16454A magnetic material test fixture 3 4 Measurement system using the 16454A magnetic materia
34. unction based on simula tion results is used in the E4991B Option E4991B 002 material measurement firmware Also residual impedance which is a major cause for measurement error cannot be entirely removed by open and short compensation This is why PTFE is provided as a load compensation device i13 d 215mm 0 3 mm lt t lt 3mm M x Figure 15 Applicable MUT size 16453A rey M P Figure 16 Structure of the 16453A 2 5 4 Principal specifications Table 8 Principal specifications of the 16453A 1 MHz to 1 GHz 42 V Frequency Max voltage Operating temperature 55 C to 150 C Terminal configuration 7 mm Compensation Must be accompanied by the E4991B with Options E4991B 002 and E4991B 007 Open short and load The principal specifications are shown in Table 8 Figures 17 and 18 show the measurement accuracy when the E4991B is used Further details about the measurement accuracy can be obtained from the operation manual supplied with the instrument 2 5 5 Operation method Figure 19 displays the flowchart when using the 16453A and E4991B for permittivity measurements The steps in the flowchart are described here For further details please refer to the Quick Start Guide for the E499 1B START v r gt 1 Select the measurement mode J v 2 Input thickness of MUT v f oy 3 Set th
35. will reduce the airgap and increase measurement precision The MUT must be smooth and not transform under applied pressure f N 4 eiu rh MMC t gt t Cut out for the positioning of the thin film electrode Electrode 97 Back Dielectric q p material Electrode 319 Front FA T Pn 245 13 NE l T fug cos p ae 70 Unit mm L J Figure 21 Fabricated thin film electrode s size C NW N J Figure 22 Positioning of the fabricated thin film on the MUT Another point to consider is the adjusting mechanism of the upper electrode s spring pressure The spring s pressure should be as strong as possible in order to minimize the occurrence of the airgap between the MUT and the electrodes However MUTs which transform under extreme pressure cannot be measured correctly since the thickness is affected To achieve stable measurements the spring pressure should be set at a level that does not transform the MUT 2 5 7 Sample measurements As shown in Figure 23 a measure ment result for glass epoxy frequency characteristic can be obtained by using the E4991B with the 16453A 100 0 Ref 4 500 Pun IER Qoo V Ref 30 00 m 5 000 1 100 00000 MHz 4 5208 1 100 00000 MHz 16 096 m 1 Star Hr Oscso0mv Figure 23 Frequency response of glass epoxy e 4 5 3 Permeability Evaluation 3 1 Definition of permeability Permeability describes the int
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