© The Institution of Electrical Engineers
The situation with regard to the basic electrical SI units has changed remarkably over the past five years. Emphasis has shifted from the definition of the ampere and its realisation using a current balance to realisation of the electrical watt in terms of the mechanical watt, or the volt in terms of mechanical potential energy, because these latter routes offer sub-part-per-million accuracy. Measurements of fundamental constants which involve a mixture of electrical and mechanical units have provided another accurate way of relating electrical units to the metre, kilogram and second. Moreover, once they have been realised in these new ways, the electrical units can be maintained, using the Josephson and quantum Hall effects, with 1 in 108 precision. The paper describes the hundredfold improvement in the accuracy with which the electrical SI units can now be realised, conserved and disseminated and which culminated in the change in the values of the maintained reference standards which took place on 1st January 1990.
References
-
-
1)
-
M. Samuel
.
(1988)
Phys. Rev. Lett..
-
2)
-
B.P. Kibble
.
New amps for old.
Electron. & Power
,
136 -
139
-
3)
-
W.K. Clothier ,
G.J. Sloggett ,
H. Bairnsfather ,
M.F. Currey ,
D.J. Benjamin
.
A determination of the volt with improved accuracy.
Metrologia
,
9 -
46
-
4)
-
E.R. Cohen ,
B.N. Taylor
.
The 1986 adustment of the fundamental physical constants.
Rev. Mod. Phys.
,
1121 -
1148
-
5)
-
Kaarls, R., Kibble, B.P., Taylor, B.N., Witt, T.J.: `Report to the CCE from the working group on the Josephson effect', Rapport BIPM-88/7, August 1988.
-
6)
-
P. Seyfried ,
R. Balhorn ,
M. Kochsiek ,
A.F. Kozdon ,
H.-J. Rademacher ,
H. Wagenbreth ,
A.M. Peuto ,
A. Sacconi
.
The Avogadro constant — recent results on the molar volume of silicon.
IEEE Trans. Instrum. Meas.
,
161 -
165
-
7)
-
B.D. Josephson
.
(1962)
Phys. Lett..
-
8)
-
V.T. Funck ,
V. Sienknecht
.
Darstellung der Spannungseinheit Volt mit der PTB-Spannungswaage.
Elecktrizitäts-wirtschaft
,
104 -
106
-
9)
-
Delahaye, F., Endo, T., Jones, O.C., Kose, V., Taylor, B.N., Wood, B.M.: `Report to the CCE from the working group on the quantum Hall effect', Rapport BIPM-88/8, August 1988.
-
10)
-
I.A. Robinson ,
B.P. Kibble ,
J.H. Belliss ,
L.C.A. Henderson
.
Towards a transportable voltage standard based on a mercury cell.
IEEE Trans. Instrum. Meas.
-
11)
-
N. Elnekave ,
A. Fau ,
F. Delahaye
.
(1976)
, Evaluation provisoire du coefficient 2e/h à partir de la dètermination absolue devolt.
-
12)
-
B.N. Taylor
.
The possible role of the fundamental constants in replacing the kilogram.
IEEE Trans. Instrum. Meas.
-
13)
-
P. Vigoureux
.
A determination of the gyromagnetic ratio of the proton.
Proc. Roy. Soc.
,
72 -
79
-
14)
-
I.K. Harvey
.
A precise low temperature DC ratio transformer.
Rev. Sci. Inst.
,
1626 -
1629
-
15)
-
C.A. Hamilton ,
R.L. Kautz ,
R.L. Steiner ,
F.L. Lloyd
.
A practical Josephson voltage standard at 1 V.
IEEE Device Lett.
,
623 -
625
-
16)
-
Delahaye, F.: `Technical guidelines for reliable measurements of the quantized Hall resistance', Rapport BIPM-88/9, August 1988.
-
17)
-
E.R. Williams ,
G.R. Jones ,
J.-S. Song ,
W.D. Phillips ,
P.T. Olsen
.
Report on the new NBS determination of the proton gyromagnetic ratio.
IEEE Trans. Instrum. Meas.
,
163 -
167
-
18)
-
A. Hartland
.
Quantum standards for electrical units.
Contemp. Phys.
,
477 -
498
-
19)
-
B.P. Kibble ,
G.J. Hunt
.
A measurement of the gyromagnetic ratio of the proton in a strong magnetic field.
Metrologia
,
5 -
30
-
20)
-
B.P. Kibble ,
G.H. Rayner
.
(1984)
, Coaxial AC bridges.
-
21)
-
I.A. Robinson
.
An optical-fibre ring interface bus for precise electrical measurement.
Meas. Sci. and Technology
-
22)
-
C.H. Dix ,
A.E. Bailey
.
Electrical standards of measurement. Part 1. DC and low-frequency standards.
Proc. IEE
,
1018 -
1036
-
23)
-
B.P. Kibble
.
Electrical standards.
J. Phys. E.
,
373 -
379
-
24)
-
K. Von Klitzing ,
G. Dorda ,
M. Pepper
.
New method for high accuracy α determination based on quantised Hall resistance.
Phys. Rev. Lett.
,
494 -
497
-
25)
-
J.C. Gallop
.
Developments in HTS devices.
Supercond. Sc. Technol.
,
20 -
25
-
26)
-
A.H. Cook
.
A determination of the density of mercury.
Phil. Trans. Roy. Soc.
,
125 -
154
-
27)
-
B.P. Kibble
.
A modification to a precision balance incorporating substitution weighing and feedback control which gives improved accuracy and convenience.
Metrologia
,
1 -
5
-
28)
-
B.V. Hamon
.
A 1–1000 ohm built-up resistor for the calibration of standard resistors.
J. Sci. Instrum.
,
450 -
453
-
29)
-
V. Bego ,
J. Butorac ,
G. Gasljevic ,
K. Poljancic
.
Volt balance realisation of the volt at ETF in Zagreb.
IEEE Trans.
,
185 -
189
-
30)
-
J. Niemeyer ,
J.H. Hinken ,
R.L. Kautz
.
Microwave-induced constant-voltage steps at one volt from a series array of Josephson junctions.
Appl. Phys. Lett.
,
478 -
480
-
31)
-
B.W. Petley ,
B.P. Kibble
.
A proposed method of measuring γP' in terms of the quantum of magnetic flux: a route to α.
Metrologia
,
167 -
170
-
32)
-
T.J. Quinn
.
News from the BIPM.
Metrologia
,
69 -
74
-
33)
-
P.T. Olsen ,
V.E. Bower ,
W.D. Phillips ,
E.R. Williams ,
G.R. Jones
.
The NBS absolute ampere experiment.
IEEE Trans. Instrum. Meas.
,
175 -
181
-
34)
-
B.P. Kibble ,
I.A. Robinson ,
J.H. Belliss
.
A realisation of the SI watt by the NPL moving-coil balance.
Metrologia
,
173 -
192
-
35)
-
T. Kinoshita
.
Accuracy of the fine-structure constant.
IEEE Trans. Instrum. Meas.
,
172 -
174
http://iet.metastore.ingenta.com/content/journals/10.1049/ip-a-3.1991.0027
Related content
content/journals/10.1049/ip-a-3.1991.0027
pub_keyword,iet_inspecKeyword,pub_concept
6
6