PRECISION HADDAD-TYPE CALCULABLE RESISTORS J. Kucera, E. Vollmer, - - PowerPoint PPT Presentation

1 CPEM 2008 Precision Haddad-type calculable resistors

PRECISION HADDAD-TYPE CALCULABLE RESISTORS

• J. Kucera, E. Vollmer, J. Schurr

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Motivation

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Calculable resistor

• Calculable frequency dependence simple construction

– Coaxial resistors

• Resistance versus length of resistor

– Bifilar, quadrifilar, octofilar resistors

• Short time stability
• Low Temperature coefficient and Load coefficient

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Haddad type resistor

• Coaxial model – boundary conditions
• Transmission line effect
• Skin effect in the inner conductor
• Thin high-resistive wire
• Thick low-resistive support
• Skin effect and eddy currents in the outer conductor

Haddad’s resistor

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Construction of the new resistor

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Connections in the inner conductor

Available technology:

• Spot welding

– No local change of metallurgy

• Hard soldering + soft tin-soldering

– Silver layer added, aggressive flux used – cleaning – Linear frequency dependence?

• Electrogalvanization + soft tin-soldering

– Silver layer added, aggressive liquid used during process

• Crimping

– Materials not melted, higher contact resistance (up to 250 mOhm)

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Spot welding IsaOhm 20 um & IsaOhm 100 um

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Spot welding IsaOhm 100 um & Brass tube 1 mm

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Hard soldered silver IsaOhm 100 um

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Galvanized silver IsaOhm 100 um

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Frequency dependence of the connection point

Contact resistance as a function of freq = 1 … 100 kHz

0.2 mOhm ~ 0.2 ppm for 1 kOhm

• 5

5 10 15 20 25 1000 100000 Frequency (Hz) delta R(f) - R(f=1000Hz) (mOhm) 10x 100 um IsaOhm crimped 2x 20 um Isaohm hard-soldered 2x 20 um IsaOhm hard-soldered, 3.5 Ohm contact resistance Slope 0.2 mOhm / 1 kHz

0.2 mOhm / 1 kHz

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Rnominal = 1290,64… Ohm

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Results of comparison measurements

• AC coaxial ratio bridge
• Measurement Ra/Rb -1, uncertainty 1.8x10-8
• Frequency range 1 to 5 kHz
• HR 1000 and HRC 1000 compared with

– Bifilar 1 kOhm

– Vishay 1 kOhm

HR 1000 – hard-soldered and spot-welded HRC 1000 – crimped and spot-welded

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Comparison of BIF, HR, HRC

BIF – Bifilar hard soldered, HR – Haddad hard soldered, HRC – Haddad crimped

• 0.1

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1000 2000 3000 4000 5000 6000 Frequency (Hz) BIF1000/HRC1000 HR1000/HRC1000 Ra/Rb-1 x10-6 (-)

large linear freq. dependence: Haddad type or BIF 1000?

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Comparison of Vishay, HR, HRC

Vishay – CTU in Prague, HR – Haddad hard soldered, HRC – Haddad crimped no significant frequency dependence for HR 1000 and HRC 1000 found

• 0.03
• 0.02
• 0.01

0.00 0.01 0.02 0.03 1000 2000 3000 4000 5000 6000 Frequency (Hz) Ra/Rb-1 x10-6 (-) CTU 1k / HRC 1000 CTU 1k / HR 1000 CTU 1k / HRC 1000 repeat

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Characteristics of new Haddad resistors

HR 1000 HRC 1000 HR 1290.6

Nominal value R (Ω)

1000 1000 1290.64

Resistance wire diameter (µm)

20 20 20

Resistance wire length (mm)

225 225 291

Temperature coefficient Tc (ppm/K), in air

• 0.26±0.07
• 1.74±0.07
• 0.52±0.17

Load coefficient Lc (.10-9/mW), in air

• 384±21
• 343±21
• 389±82.4

Frequency dependence dc-1.592 kHz, in air

4.09e-010 4.09e-010 4.15e-010

Frequency dependence dc-1.592 kHz, in sil. oil

4.38e-010 4.38e-010 4.96e-010

Measured values Calculations between potential ports plains

17 CPEM 2008 Precision Haddad-type calculable resistors delta_R_o / R verursacht durch Wirbelstrom und Skin-Effekt im Außenleiter eines koaxialen, berechenbaren Widerstands (ANSYS für e = 0 und Beitrag nach Carter für e = 1 mm)

1.0E-15 1.0E-13 1.0E-11 1.0E-09 1.0E-07 1.0E-05 1.0E-03 1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 Frequenz in Hz delta_R_o / R e = 0 mm e = 1 mm

Excentricity of the inner conductor

Eckhard Vollmer

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Conclusion

• Modified Haddad resistor designed to have these advantages:

– negligible freq. dependence – easily adjusted – can be dismantled

• Two 1 kOhm and one 1.29064 kOhm resistors realized

– with crimped, spot-welded and hard-soldered connection

• Frequency dependence comparison with Bifilar 1 kOhm

– large linear freq. dep. found in the bifilar resistor

• Frequency dependence comparison with Vishay 1 kOhm

– small freq.dep. of HR 1000 and HRC 1000 verified

• Load and temperature coefficient determined
• Frequency dependence of connection points tested

– crimped, hard-soldered, spot-welded connections – no significant frequency dependence found

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Acknowledgment

• Thanks for helpful support and comments:
• J. Schurr, E. Vollmer, G. Muchow, P. Warnecke, V. Bürkel, P. Hinze,
• J. Kopton, B. H. Schumacher, G. Ramm, F. J. Ahlers, Bryan Kibble and others.
• Financial and technical support:
• PTB in Braunschwieg, Department 2.6
• Leonardo da Vinci programme "GOAL-S 2005-2007"

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