100 μ  1  100  10 k  1 G  100 T  1 T  1 M  A Bridge for Scaling to High Resistance from the QHR Rand Elmquist (presenter) and Dean Jarrett (co-author) NIST Electronics and Electrical Engineering Laboratory, Gaithersburg, MD

Introduction  Overview of NIST resistance scaling  Cryogenic current comparator (CCC) bridges  High resistance CCC bridges  Design  Results  Verification Uses with 1 M  special tests/comparisons, improved NIST standards up to 1 T , and Warshawsky bridge

Current comparators Hamon-type transfer standards ▪ N -to- n (commercial) ▪ 10-to-1 and 100-to-1 (NIST-built) Quantized Hall resistance (QHR) with the Cryogenic current comparator (CCC) for most resistance ranges 1  to 1 M  100 μ  1  100  10 k  1 G  100 T  1 T  1 M  Summary: NIST Scaling 2003 Active-arm Bridge

1  Thomas standards based 1  Bank (Thomas) 10 k  100  1 M  100 M  0.1 m  to 1 k  1 G  to 1 T  10 M  1 k  to 100 k  DCC bridges Hamon transfer devices Hamon transfer devices Hamon transfer devices NIST resistance scaling (up to 1990)

QHR-based scaling – 4-terminal Cryogenic Current Comparator bridges QHR standard =  100  standards (Four-terminal) 1  (51130C) 10 k  (51131C) 100  (51138C) CCC bridges CCC bridge QHR SQUID NSNS NPNP NFNF RFRF RSRS D DVM CCC magnetic shield Primary current source Secondary current source 4-terminal bridge

QHR standard =  1 M  standards (Two-terminal) 100  standards (Four-terminal) 1  (51130C) 10 k  (51131C) 100  (51138C) 1 M  (51142C) 100 M  (51145C) 0.1 m  to 1 k  (51132C to 51138C) 1 G  to 100 T  (51147C & others) 10 M  (51143C) 1 k  to 100 k  (51139C to 51141C) DCC automatic bridge Hamon devices Hamon devices, Active-Arm Bridge Hamon devices CCC bridges CCC bridge Scaling Paths for NIST Resistance Calibration Services (2003)

R U or R S RDRD E 2 (B) E 1 (A) D Active-arm bridge Two-terminal CCC RURU RSRS Winding 1 S Winding 2 CCC analog with single ramping source two current detectors Active-arm bridge with two active sources one current detector L. C. Henderson, “A new technique for the automated measurement of high valued resistors,” J. Phys., Electron., Sci. Instrum., vol. 20, pp , Sept R. F. Dziuba, B. F. Field, and T. F. Finnegan, “Cryogenic voltage comparator system for 2e/h measurements,” IEEE Trans. Instrum. Meas., vol. 23, pp , “New” High Resistance Bridges

NSNS NPNP NFNF RPRP RFRF Single ramping current source QHR Superconductor dc SQUID Copper wire Phosphor-bronze wire Two-terminal Cryogenic Current Comparator Bridge CCC shield R 2 ≈ 3  R 1 ≈ 3 

RSRS R H /2 RSRS RSRS RSRS RSRS RSRS RSRS RSRS Magnetic Field I A = I – I B – I C I B ≈ I ×(R S /R H ) I C ≈ I ×(R S /R H ) 2 Two-terminal (Multiple-connection) QHR equivalent circuit R S = Contact and Lead Resistance QHR R H /2

Hamon 10 k  /1 M  Comparison, NIST Hamon H100KA Trend Chart

NIST Reference #701 NIST Hamon HD1M Measurement Uncertainty Type A : <0.05 ppm Type B : ≈ 0.02 ppm 1 M  vs. NIST QHR standard

1 M  Reference Resistor S/N 702: Trend Chart

1 M  / 100 M  Hamon Device J/8 Trend Chart at 1 M 

The CCC can calibrate any 1 M  standard for use as transfer, working, or check standard.  Hamon devices used at high resistance levels 10 M  and 100 M   Warshawsky bridge standards at 1 M   Special-test customer standards  Laboratory comparison transport standards Primary Benefits – 1M  CCC Hermetically Sealed NIST standards and high-value Hamon devices

Substitution method – Active-arm bridge replaces TeraOhmmeter, and 1 M  Warshawsky bridge replaces 6-position Ring Method cancels errors Improved air-type standards for 1 M  and high resistance levels better predictability Cryogenic current comparator  fixed or Hamon standards referenced directly to QHR Improved Methods for 1M  and higher resistance QHR standard =  1 M  standards (Two-terminal) 100  standards (Four-terminal) CCC bridge