towards uniformity of dc voltage metrology within sim
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VIII SEMETRO
Towards Uniformity of DC Voltage Metrology within SIM
Yi-hua Tang Quantum Electrical Metrology Division
National Institute of Standards and Technology Gaithersburg, MD 20899
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OutlineDC voltage metrology status within SIMJVS Comparison
MAPIndirect comparisonDirect comparison
Summary Future perspective
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Lab / Country No. of JVS
NIST / USA 4 (20)
NRC / Canada 1
CENAM / Mexico 1
INMETRO / Brazil 1
INTI / Argentina 1
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Principle of JVS
V = nf / KJ-90
f: frequency
KJ-90 = 2e/h = 483 597.9 GHz/V Josephson constant
n: integer
BIPM.EM-K10.a JVS at 1.018VBIPM.EM-K10.b JVS at 10 VBIPM.EM-K11.b Zener at 10 VSIM.EM.BIPM-K11.a Zener at 1.018 VSIM.EM.BIPM-K11.b Zener at 10 V SIM.EM.BIPM-K10.b JVS at 10V
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MAP Example 1: NIST-BIPM JVS comparison at 10 V
3 system comparison:BIPMNIST-GaithersburgNIST-BoulderOct. 1998 – Jan. 1999BIPM.EM-K11.b
Pressure corrections applied.
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d (μV) uc (μV) (k = 1)
NIST(G) - BIPM 0.26 0.14
NIST(B) - BIPM 0.22 0.17
NIST(G) – NIST(B) 0.04 0.13
Results of BIPM.EM-K11.b
Uncertainty: 1 - 2 parts in 108
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INMETRO JVS system
Established in 1998
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y = -0.00565391x + 295.00550325
97.1
97.2
97.3
97.4
97.5
97.6
9/3 9/8 9/13 9/18 9/23 9/28 10/3 10/8 10/13
Off
set f
rom
1.0
18V
(μV)
Date
Z3 INMETRO
NIST
Linear (INMETRO)
y = -0.02007355x + 827.94375914
125.6
125.8
126.0
126.2
126.4
126.6
9/3 9/8 9/13 9/18 9/23 9/28 10/3 10/8 10/13
Off
set f
rom
1.0
18V
(μV)
Date
Z5 INMETRO
NIST
Linear (INMETRO)
y = 0.01066458x - 280.46730707
92.1
92.2
92.3
92.4
92.5
92.6
9/3 9/8 9/13 9/18 9/23 9/28 10/3 10/8 10/13
Off
set f
rom
1.0
18V
(μV)
Date
Z6
INMETRO
NIST
Linear (INMETRO)
y = 0.00224443x + 35.74730979114.0
114.1
114.2
114.3
114.4
114.5
9/3 9/8 9/13 9/18 9/23 9/28 10/3 10/8 10/13
Off
set f
rom
1.0
18V
(μV)
Date
Z7INMETRO
NIST
Linear (INMETRO)
INMETRO-NIST JVS Comparison at 1.018VSept. to Oct. 1999Protocol: MAP SIM.EM.BIPM-K11.a
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Source Uncertainty (μV)Pooled Type A of INMETRO, uA
INMETRO 0.003Pooled Type A of NIST, uA
NIST 0.006Standard deviation of mean of four Zener differences uB
INMETRO -NIST0.011
Type B uncertainty from INMETRO and NIST JVS systems, uB
INMETRO, NIST0.016
Expanded uncertainty (k = 2) 0.049
cu = 2 2AINMETRO(u ) + 2
ANIST(u ) +
2
B
INMETRO−NIST(3.18
2 u ) + 2BINMETRO, NIST(u )
Z3 Z5 Z6 Z7
INMETRO - NIST 0.023 0.052 0.001 0.013
Δ(INMETRO− NIST ) =(Vi(predict) − Vi(NIST )[ ]
13∑
13
VNISTINMETROMean μ022.0)( =−
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Question:
Is MAP good enough for JVS comparison?Answer:
No
Why?1. JVS uncertainty: few parts in 1010
MAP uncertainty: few parts in 108
2. Uncertainty using MAP limited by Zener characteristicsEnvironmental effects• Pressure• Temperature• Relative humidity
Zener intrinsic noiseShipping impact
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Question:
How can we improve the situation?Answer:
Develop a transportable JVS
8.5”
Net weight: 50 lbGross weight: 120 lb
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NIST-CENAM SIM.EM.BIPM-K11.bNIST CJVS in CEMETRO, March 2006
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Dionisio HernándezEnrique Navarrete David AvilésYi-hua Tang
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Results of NIST-CENAM SIM.EM.BIPM-K11.b
No pressure correction needed.
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d (μV) uc (μV)
CENAM - NIST -0.035 0.043
NIST - BIPM 0.26 0.28
CENAM - BIPM 0.23 0.28
DCENAM-BIPM = (dNIST-BIPM + dCENAM-NIST )
UCENAM-BIPM = (UNIST-BIPM2 + UCENAM-NIST
2)1/2
To establish a link between CENAM and BIPM
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Question:
Is indirect JVS comparison good enough?Answer:
No
Why?JVS uncertainty: few parts in 1010
Indirect JVS comparison uncertainty: few parts in 109
Uncertainty limited by Zener noise
Environmental effects• Pressure• Temperature• Relative humidityZener intrinsic noiseShipping impact
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Question:
How can we improve the situation?Answer:
Do not use Zener as transfer standards. Make direct JVS comparison.
Protocol:
BIPM JVS comparison Option a; BIPM JVS comparison Option b;Alternative protocols
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An alternative protocol
Step 1 Step 2
Step 3 Step 4
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NIST-NRC SIM.EM.BIPM-K10.b
Barry Wood of NRC
NIST CJVS at NRC August 2007
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Link between NIST and BIPM via NRC
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-11
-9
-7
-5
-3
-1
1
3
5
7
9
11
0 5 10 15 20 25 30 35 40
Meas. number
U (N
IST)
- U
(BIP
M) /
nV #1 to #5#6 to #8#9 to #10#11 to #15#16 to #25#26 to #30#31#32 to #37
NIST-BIPM JVS comparison BIPM.EM-K10.b
BIPM protocol Option B
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Histogram of the JVS comparison
BIPM protocol Option B
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-10
-8
-6
-4
-2
0
2
4
6
8
10
12
0 5 10 15 20
Measurements
U(N
IST)
- U
(BIP
M) /
nV
#1 to #11#12 to #22
NIST-BIPM JVS comparison BIPM.EM-K10.b
BIPM protocol Option A
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Option B Measured by NIST
Option A Measured by BIPM
Difference (nV) -0.074 -1.53
Type A (nV) 0.68 0.75
Type B (nV) 0.93 0.77
Combined uncertainty (nV) 1.15 1.07
U (NIST) – U (BIPM) / nV
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Direct link between NIST and BIPM
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BIPM JVS in NIST March 2009
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Stephane Solve Regis ChayramyYi-hua Tang
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Vd = Va1 – Va2 = (N1 f1 – N2 f2 ) / KJ-90
Vd - Vm = Vo + mt + Vn + δ
δ
= Vd – Vm – Vo – mt – Vn
Model of NIST protocol
Automatic JVS direct comparison
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Automatic JVS direct comparison
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Example: automatic comparison
nominal voltage: 9.997 V
217 points in 14 h. U (NIST) – U (BIPM) / nV ua / nV
0.02 0.24
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Not listed in BIPM KCDB
BIPM.EM-K10.b
SIM.EM.BIPM-K11.bSIM.EM.BIPM-K10.b
BIPM.EM-K10.a
BIPM.EM-K11.b
Summary
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MAP(Indirect)
CJVS(Indirect)
JVS vs. JVS(Direct)
PJVS vs. PJVS(Future)
Voltage range Up to 10 V Up to 10 V Up to 10 V Up to 10 V
Uncertainty 2 x 10-8 2 x 10-9 1 -
7 x 10-10 parts x 10-11
Limiting factor Zener Zener(1/f noise)
Null detector Null detector
Time needed Weeks Days Hours Hours
Expense Low High High Potentially low
Comparison of various protocols
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Future perspective
Coming soon: new 10 V PJVS
Expected uncertainty: few parts in 1011
at 10 V
Detection of small system error is possible
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