EUROMET Comparison of a 10 mH Inductance Standard at 1 kHz

EUROMET Comparison
of a 10 mH Inductance Standard at 1 kHz
EUROMET.EM-K3
Final Report
by
Axel Kölling
Physikalisch-Technische Bundesanstalt
Bundesallee 100, D-38116 Braunschweig, Germany
May 2011
Summary
This report describes the organization, the equipment and the results of a EUROMET comparison of a
10 mH inductance standard at a frequency of 1 kHz which took place in 2006. The participants were
PTB (Germany), INM (Romania) and NCM (Bulgaria). Comment: NCM is now BIM, Bulgarian Institute
of Metrology
The participation of PTB made it possible to have a link to the key comparison CCEM-K3.
Although the methods of measurement differed in all participating laboratories, an agreement within
the respective limits of uncertainty could be achieved by all participants. The results of each participant
are referred to the Key Comparison Reference Value (KCRV), stated in the CCEM-K3 final report.
PTB Germany
EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
Contents
Contents...................................................................................................................................................2
Introduction..............................................................................................................................................3
1. Participants and organization...............................................................................................................3
1.1 Participants.........................................................................................................................................3
1.2 Co-coordinator....................................................................................................................................3
1.3 Time schedule.....................................................................................................................................4
1.4 Transportation.....................................................................................................................................4
2. Travelling standard...............................................................................................................................4
2.1 Description of the standard.................................................................................................................4
2.2 Quantities to be measured..................................................................................................................6
2.3 Measurement instructions...................................................................................................................6
3. Description of measuring methods.......................................................................................................6
3.1 Measuring method at PTB..................................................................................................................6
3.2 Reference standard and the traceability to the SI at PTB..................................................................7
3.3 Measuring method at INM...................................................................................................................8
3.4 Reference standard and the traceability to the SI at INM...................................................................8
3.5 Measuring method at NCM.................................................................................................................8
3.6 Reference standard and the traceability to the SI at NCM.................................................................8
4. Measurement results............................................................................................................................8
4.1 Results of the participants and degree of equivalence with respect to CRV......................................8
4.2 Link to the CCEM-K3 and degree of equivalence with respect to KCRV...........................................9
4.3 Correlation.........................................................................................................................................10
5. Measurement uncertainty...................................................................................................................10
6. Conclusion..........................................................................................................................................10
7. Reference............................................................................................................................................10
Appendix A Summary of uncertainty budgets........................................................................................11
Appendix B Technical protocol...............................................................................................................16
Page 2 of 20
Introduction
The comparison was organized within the framework of Phare 2002 Project BG0201.12
“Strengthening of the National Conformity Assessment System – Technical Assistance for
Standardization and Metrology”, EUROPE Aid/116486/D/SV/BG.
The comparison was linked to the corresponding CCEM comparison CCEM-K3 [1].
Three national metrology institutes took part in this comparison: PTB (Germany), NCM (Bulgaria) and
INM (Romania).
PTB acted as the pilot laboratory and in this function was responsible for providing the travelling
standard, the evaluation of the measurement results and the final report. NCM was responsible for the
protocol.
The comparison was accomplished in accordance with the EUROMET Guidelines on Conducting
Comparisons and CCEM Guidelines for Planning, Organizing, Conducting and Reporting Key,
Supplementary and Pilot Comparisons.
1.
Participants and organization
1.1
Participants
PTB (DE)
Contact persons:
Names:
Jürgen Melcher, Axel Kölling
Address:
Physikalisch-Technische Bundesanstalt (PTB) Bundesallee 100
D-38116 Braunschweig
Germany
Telephone:
+49 (531) 5 92 2100
Fax:
+49 (531) 5 92 2105
e-mail:
Juergen.Melcher@PTB.DE
Axel.Koelling@PTB.DE
NCM (BG)
Contact person:
Names:
Petya Aladzhem, Georgy Simeonov
Address:
BIM - National Centre of Metrology (NCM) 52-B G.M.Dimitrov blvd.
1040 Sofia
BULGARIA
Telephone:
+359 2 9702 747
Fax:
+359 2 9702 735
e-mail:
p.aladzhem@bim.government.bg
INM (RO)
Contact person:
Name:
Anca Nestor
Address:
National Institute of Metrology (INM) sos. Vitan Barzesti 11 sector 4
042122 Bucuresti
ROMANIA:
Telephone:
+40 21 334 48 30
Fax:
+40 21 334 55 33
e-mail:
Anca.Nestor@INM.RO
1.2
Co-coordinator
Name:
Address:
Telephone:
Axel Kölling
Physikalisch-Technische Bundesanstalt (PTB) Bundesallee 100
D-38116 Braunschweig
Germany
+49 (531) 5 92 2115
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
Fax:
e-mail:
1.3
+49 (531) 5 92 2105
Axel.Koelling@PTB.DE
Time schedule
Starting date:
First measurements at PTB:
Measurements at INM:
Measurements at NCM:
Final measurements at PTB:
1.4
April 2006
From 16 to 20 February 2006
From 12 June to 7 July 2006
From 24 July to 4 August 2006
September 2006
Transportation
The travelling standard was taken as carry-on luggage by aeroplane from Germany to Romania. An
NCM car was used for transportation from Romania to Bulgaria. Transportation of the standard back to
Germany by car was organized by NCM. The standard was accompanied by an ATA – carnet in order
to solve custom formalities.
2.
Travelling standard
The travelling standard was an inductance standard with a nominal value of 10 mH. It is a General
Radio 1482-H 10 mH inductance standard encased by a temperature-regulated enclosure.
The thermostated device together with a power supply unit guarantees a constant operating
temperature during the transportation . A set of batteries (2 pieces, 6 V lead storage battery) or the
car’s supply system of 12 volt (in the case of transportation by car) was used.
2.1
Description of the standard
Table 1: Description of the standard
Type
Manufacturer
Serial number
Nominal value of inductance
Relative instability of inductance
Nominal thermostatic temperature
GR 1482-H Inductance Standard
General Radio, enclosure ASMW
№01
10 mH ± 0.1%
< 1 µH/H per year
30.0 °C± 0.2 K
Instability of thermostatic temperature with an instability of
the ambient air temperature of 0.5 K
± 0.01 K per year
Dependence of the value of inductance on the ambient air
temperature in the range from 18 °C to 28 °C
≤ 0.3 ppm per K
Measuring frequency
Measuring voltage
1 000 Hz
≤ 0.5 V
Effective resistance (DC) of the coil at an ambient air
temperature of 23.0 °C ± 0.1 K
8.671 Ω
Width of the HIGH and LOW connecting terminals
19 mm
Connection system
Two terminals (case is internally
connected with LOW terminal)
Power supply of thermostat:
• power supply unit (230 V ± 10%; 50 Hz);
• set of batteries (2 x 6 V);
• 12 V supply system of a car
0.5 A at 12 V (DC)
Power cable
Red plug to be connected to plus,
blue plug to be connected to minus
Dimensions of leather bag
Total mass
470 mm x 300 mm x 400 mm
Approx. 38 kg
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EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
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EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
2.2
Quantities to be measured
The quantities to be measured were:
− L: inductance of the standard (two terminals);
− R: DC resistance of the inductor coil;
− f: measurement frequency;
− Text: the temperature (°C) of the environment where the standard is measured.
2.3
Measurement instructions
The measurements should be performed under the following conditions:
− Measurement frequency: 1000 Hz;
− Measuring voltage: <0.5 V (rms);
− Temperature of the environment: 23°C ± 1°C;
− Relative humidity: between 30 % and 70 %.
3.
Description of measuring methods
3.1
Measuring method at PTB
Inductance measurements at PTB are carried out with a Maxwell-Wien Bridge. This bridge has the
advantage, that to a first order the bridge equation (1) is independent of frequency. But measurements
at a frequency of 1 kHz require an investigation of higher order effects, i.e., lumped impedances must
be taken into account.
H
RW1
CW1
R1
C1
R2
C1A
T
DW
LW3
G
D
H
RW3
LX
R3
C4
RX
CW3
L
L
Page 6 of 20
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
The main arms of the bridge contain, besides the DUT, represented by the element LX and RX, the
fixed capacitor C1, the variable capacitor C1A, the two fixed resistors R2 and R3 and the variable resistor
R1 .
The main bridge balance (equ. (3)) is achieved with components C1A and R1.
The bridge is adapted to the value of inductor LX by exchanging C1, R2 and R3.
LX ≈ C1 ⋅ R2 ⋅ R3
(1)
The impedance of the resistors can be characterized by
Zn ≈ Rn (f ) ⋅ (1 + jωτ n )
(2)
With the impedances Z2 and Z3 the bridge equation leads to
R X + jωLX =
Z2Z3 (1 + jω (C1 + C1A )Z1 )
Z1 − jωC4 Z 2Z3 (1 + jω(C1 + C1A )Z1 )
(3)
The capacitance C4 characterizes only the stray capacitance at the bridge terminals. The inherent
parallel capacitance of the inductor is not included in C4.
To eliminate the main effects of the time constants τn, a zero-substitution method is employed:
Inductor LX is replaced by a relatively small inductor LX0, and C1 is removed. The value C1A0 for C1A is
obtained to balance the bridge. The Value C40 can be different to C4 because of different connection to
the main measurement.
This procedure results in the model equation that approximates LX within the uncertainties of the
calibration.
LX = (C1 + C1A )R2 R3 − C1A0 R2 R3 + LX0
− ω 2 R 2 R3C1τ 2τ 3
2
− ω 2 R22 R32(C4(C1 + C1A )2 − C40C1A0
)
(4)
R22 R32
+ (C4 − C40 )
R12
A potential problem in Maxwell-Wien Bridge circuits is that of stray capacitance between either
connecting point of the null detector and ground potential. The best solution for solving this problem is
to insert a Wagner earth. This voltage divider is designed to have the same voltage ratio and phase
shift as each side of the bridge. These circuit elements have the index “W”. Because the midpoint of
the Wagner divider is directly grounded, the Wagner balance forces the null detector to be at virtual
ground potential, without a direct connection between the detector and the ground.
3.2
Reference standard and the traceability to the SI at PTB
The reference standards are represented by the components C1, R2 and R3. The capacitor C1 is traceable to the Thompson-Lampard Capacitor of PTB. The two resistors are traceable to the quantized
Hall resistance via calculable AC/DC transfer resistors of PTB.
Page 7 of 20
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
3.3
Measuring method at INM
The equivalent series inductance of the standard inductor is measured in two-terminal connection by
substitution against the equivalent series inductance of one 10 mH reference standard using a digital
LCR-meter, type HP 4284 A.
The DC resistance of the inductor coil is measured directly in four-terminal connection using a digital
multimeter, type Keithley 2001.
This procedure results in the model equation that approximates LX within the uncertainties of the
calibration.
LX = (LS + ∆LScurrent + δLSdrift + δLST ) ⋅ K ⋅ K C − δLXT
3.4
1
(5)
Reference standard and the traceability to the SI at INM
The 10 mH reference standard (serial number 8602) used is an inductor built in INM in 1986.
This inductor is included in the group of transfer standards used to provide traceability on a regular
basis. The last external calibration of this standard was performed in December 2005 in INRIM, Italy.
3.5
Measuring method at NCM
A 1:1 substitution method with inductance bridge model GR 1632 A is used. The travelling and
reference standards (L and LS) are measured in turn in two-wire connection using five decades of the
bridge. The last digit of the measured values (missing in the uncertainty budget table) is estimated by
de-balancing the bridge with a step of the last decade in plus and in minus. The measurements are
made at 1000 Hz.
This procedure results in the model equation that approximates LX within the uncertainties of the
calibration.
L = (LS + δLD + δLTS ) ⋅ l K ⋅ l − δLT *
(6)
All conditions mentioned in section 4 “Measuring instructions” from the Technical Protocol are
observed.
3.6
Reference standard and the traceability to the SI at NCM
The reference standard (LS) model GR 1482 H, Ser. № 17982, is part of the national group standard.
The value of the national standard is traceable to PTB. The last calibration was in 2003.
4.
Measurement results
4.1
Results of the participants and degree of equivalence with respect to CRV
Table 2 reports the measured inductance and uncertainty given by NCM, INM and PTB, along with the
degrees of equivalence Di and their expanded uncertainty UDi for the participants NCM and INM.
The drift of the travelling standard was neglected, because the change between the first and second
measurement in PTB was very small, especially compared with the uncertainties claimed by NCM and
INM. In the following calculations, the mean value of the first and second PTB result, PTBmean, was
taken into account. For the associated expanded uncertainty, the two PTB results were looked at, as if
they were the results of two different measurements with a correlation coefficient of 1.
The degree of equivalence Di is given with respect to the PTBmean value, which is taken as the
comparison reference value (CRV):
Di = Li − LPTBmean
1
See a description of the single components in Appendix A
Page 8 of 20
(7)
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
with the expanded uncertainty :
2
U Di = U i + U PTB
(8)
2
Table 2: Results of the participants
measured
inductance,
LX
expanded
uncertainty, U(LX)
degree of
equivalence,
D
expanded
uncertainty,
UD
mH
mH
µH/H
mH
PTB1st
10.00456
6.4 ·10-5
NCM
10.0044
40 ·10-5
-12.5
40 ·10-5
INM
10.0043
60 ·10-5
-22.5
60 ·10-5
PTB2nd
10.00449
5.1 ·10-5
PTBmean
10.004525
5.7 ·10-5
participants
4.2
-
-
Link to the CCEM-K3 and degree of equivalence with respect to KCRV
The link for NCM and INM results to the key comparison reference value of CCEM-K3 is made via the
PTB measurements, as PTB or PTB (ASMW) respectively participated in both comparisons. The
applied travelling standard was one of the two standards that are used in the CCEM-K3 comparison.
In the meantime this standard was always kept under thermostated condition. PTB has a history of the
measurement values of this standard from the first measurements at ASMW up to now. The actual
measuring system of PTB achieves lower uncertainties (see table 2) then the systems of ASMW and
PTB that are used during the CCEM comparison. Measurements based on the mentioned standard
history shows that this PTB system has an exact accordance with the old ASMW measuring system.
To compare the results of NCM/INM with results of the participants in the key comparison CCEM-K3,
the Key Comparison Reference Value (KCRV), stated in the CCEM-K3 final report was referred to.
The degree of equivalence DK3,NCM/INM and expanded uncertainty UK3,NCM/INM of NCM/INM with respect to
KCRV is calculated as follows:
DK3,NCM/INM = DNCM/INM + DK3,PTB
(9)
UK3,NCM/INM = UD2NCM/INM + UD2K3/PTB
(10)
where DK3,PTB and UK3,PTB are the degree of equivalence and its expanded uncertainty of PTB (ASMW)
with respect to KCRV. The degree of equivalence and expanded uncertainty of NCM/INM with respect
to KCRV are given in Table 3.
Table 3: Degree of equivalence and expanded uncertainty of NCM/INM with respect to KCRV
participants
degree of
equivalence,
DK3,NCM/INM in µH/H
expanded
uncertainty,
UK3,NCM/INM
µH/H
in
degree of
equivalence,
DK3,PTB in µH/H
expanded
uncertainty,
UK3,PTB in µH/H
NCM
-16
41
-3
8
INM
-26
61
-3
8
Page 9 of 20
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
4.3
Correlation
The result of INM is correlated to the KCRV (section 5.1), because the reference standard of INM was
calibrated at INRIM, Italy (IEN at the time of CCEM-K3).
The result of NCM is correlated to the CRV and the KCRV, because the reference standard of NCM
was calibrated at PTB.
The uncertainties of the INM and NCM reference values are the largest contributions to the uncertainty
budgets. They are traced back via the INRIM and PTB standards to the SI. The reason for the large
uncertainties is that these standards are not thermostated, so that the temperature coefficient of the
standards which is not correlated with the INRIM or PTB measurements had the biggest influence on
the uncertainties. Therefore, the effect of correlation was neglected.
5.
Measurement uncertainty
A detailed uncertainty analysis and an uncertainty budget in accordance with the ISO Guide to the
Expression of Uncertainty in Measurement is given in Appendix A.
6.
Conclusion
The comparison EUROMET.EM-K3 was organized with the main objective of showing the international
equivalence of the as-maintained units of inductance at NCM and INM. To calculate the degree of
equivalence of the results of NCM and INM they were linked to CCEM-K3. The results obtained show
very good agreement with the reference value within the expanded uncertainties.
7.
Reference
[1] H. Eckhard, “Final Report of CCEM-K3: International Comparison of 10 mH Inductance Standards
at 1 kHz”, published online in the Key Comparison Data Base: http://kcdb.bipm.fr
Page 10 of 20
Appendix A Summary of uncertainty budgets
Acronym of institute: PTB
Date: September 2006
Remarks: Because of the two measurement periods we have to give two different groups of results.
Model equation
LX,A/B = (C1H − C1A0 )R2R3 + LX0 + TypBT
− ω 2R 2 R3C1(k2 + k3 − τ 2τ 3 )
2
− ω 2R22R32(C4HC1H − C40C1A0
)
2
R22R32
+ (C4H − C40 )
R12
C1H = C1 + C1A
ω = 2π f
C1A = c1A( 1 + TypBC )
C1A0 = c1A0( 1 + TypBC )
R1 = r1( 1 + TypBR1 )
LX0 = l X0( 1 + TypBL )
Definition of quantities
quantity
unit
definition
LXA/B
H
inductance of travelling standard
C1
F
capacitance of capacitor C1
C1A
F
capacitance of capacitor C1A
c1A
F
observations of capacitor C1A
C1A0
F
entire capacitance of zero-substitution
c1A0
F
observations of capacitor C1A0
C1H
F
entire capacitance of main measurement
C40
F
capacitance of bridge terminals in the zero-substitution
C4H
F
capacitance of bridge terminals in the main measurement
f
Hz
frequency of measurement
s
2
frequency coefficient of resistor R2
k3
s
2
frequency coefficient of resistor R3
Lx0
H
inductance of small air coil LX0
lxO
H
observations of small air coil LX0
R1
Ω
value of decade resistor R1
r1
Ω
observations of decade resistor R1
R2
Ω
value of resistor R2
R3
Ω
value of resistor R3
k2
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
quantity
unit
definition
TypBC2
TypBL
TypBR1
TypB
takes into account the uncertainty of the capacitance meter
1
takes into account the uncertainty of the inductance meter
1
1
T
ω
takes into account the uncertainty of the decade resistor R1
H
takes into account the uncertainty of the temperature stability of the
travelling standard
s-1
radian frequency of measurement
π
time constant of resistor R2
τ2
s
time constant of resistor R3
τ3
s
frequency coefficient of resistor R3
Uncertainty budget of the first measurement period
quantity
value
standard
uncertainty
C1
1.000023240·10-9 F
276·10-18 F
C1A
c1A
C1A0
c1A0
C1H
1.19118·10
-12
1.12176·10
-12
1.12176·10
-12
-15
C4H
200·10-15 F
k3
F
F
F
1.00121442·10 F
100·10
k2
F
-9
C40
f
F
100.0·10
-18
100.0·10
-18
s
2
s
2
0.8 %
10·106
17·10-9 H
8.9 %
-10·106
-21·10-9 H
22.2 %
1.73·10
F
4
2.06·10
-15
F
4
2.06·10
-15
F
4
1.75·10
-15
F
4
-15
F
∞
-76
-44·10-12 H
0.0 %
577·10-15 F
∞
-3900
-2.2·10-9 H
0.5 %
0.289 Hz
∞
57.7·10
-18
57.7·10
-18
s
2
∞
s
2
∞
∞
lX0
4.07·10-6 H
2.07·10-24 H
4
R1
1.148560·106 Ω
664 Ω
∞
r1
1.1485600·10 Ω
24.5 Ω
4
R2
999.94214 Ω
1.42·10 Ω
R3
10000.14037 Ω
9.82·10 Ω
-9
-3
-3
5200
1200
-1.4·10
-12
400·10
3
400·10
3
10·10
1.0·10
-6
∞
-15·10-12
-9
5.77·10 H
∞
H
0.0 %
23·10
-12
H
0.0 %
0.0 %
-6
4.1·10
577·10-6
23·10
-320·10-18 H
∞
0.0
0.0 %
-13·10-18
∞
TypBR
H
-12
0.0 %
-3
1.44·10
-410·10
0.0 H
57.7·10
0.0
-15
0.0
-6
TypBL
0.0 H
2.8·10-9 H
4
5.87·10 H
TypBT
10·106
F
4.07000·10 H
0.0
index
-15
LX0
6
uncertainty
contribution
1.73·10
577·10
1000.500 Hz
sensitivity
coefficient
-15
-6
TypBC
690·10
-9
-6
-9
35.8 %
-9
24.7 %
14·10 H
9.8·10 H
40·10
-12
H
0.0 %
5.9·10 H
3.6 %
-8.8·10-15 H
0.0 %
-9
-9
1.0
5.8·10 H
3.5 %
ω
6286.33 s
π
3.1415926535898
τ2
800·10-12 s
2.02·10-9 s
∞
-320·10-6
-640·10-15 H
0.0 %
τ3
800·10-12 s
2.02·10-9 s
∞
-320·10-6
-640·10-15 H
0.0 %
LA
2
1.19118·10
-12
degrees
of
freedom
26
-1
0.0100045577 H
1.81 s
-1
-9
30.9·10 H
∞
49
The quantity (value = 0) does not make a contribution to the value of LS but rather to the uncertainty.
Page 12 of 20
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
Uncertainty budget of the second measurement period
degrees
standard
quantity
value
of
uncertainty
freedom
C1
1.000023240·10-9 F 276·10-18 F
26
C1A
c1A
C1A0
c1A0
C1H
C40
C4H
f
1.20880·10
-12
1.20880·10
-12
1.15363·10
-12
1.15363·10
-12
F
F
F
F
-9
1.00123204·10 F
100·10
-15
200·10
-15
F
2
1.18·10
F
2
1.32·10
-15
F
2
1.32·10
-15
F
2
1.22·10
-15
F
2
-15
F
∞
F
∞
-15
577·10
1000.500 Hz
s
F
-15
577·10
F
-18
1.19·10
-15
2
∞
0.289 Hz
100.0·10-18 s2
57.7·10-18 s2
∞
LX0
4.05500·10-6 H
6.53·10-9 H
52
lX0
4.05500·10 H
2.89·10 H
2
R1
1.149537·10 Ω
664 Ω
∞
r1
1.1495367·10 Ω
19.2 Ω
2
R2
999.94562 Ω
1.41·10 Ω
R3
10000.19615 Ω
9.82·10 Ω
6
10·106
2.8·10-9 H
1.2 %
10·106
17·10-9 H
-4.5 %
-10·106
-13·10-9 H
4.9 %
-76
-44·10-12 H
0.0 %
-9
-3900
-1.4·10
-2.2·10 H
-12
400·10
k3
6
index
∞
100.0·10
-9
s
uncertainty
contribution
2
k2
-6
57.7·10
-18
sensitivity
coefficient
-3
-3
5200
1200
3
0.0 %
1.0
2.9·10-9 H
0.9 %
-13·10-18
-250·10-18 H
0.0 %
10·10
1.0·10
-6
-6
∞
550·10
-9
TypBL
0.0
1.44·10-3
∞
4.1·10-6
0.0
-6
577·10
∞
-12
-9
∞
5.77·10 H
ω
6286.33 s
π
3.1415926535898
τ2
800·10-12 s
τ3
LB
-12
800·10
-1
s
0.0100044907 H
-15·10
32·10
-12
H
0.0 %
5.9·10-9 H
5.2 %
-8.7·10
-15
H
0.0 %
5.0 %
-640·10-15 H
0.0 %
∞
-320·10-6
-9
∞
-6
-9
2500
Page 13 of 20
35.6 %
9.8·10 H
5.8·10 H
2.02·10-9 s
25.7·10 H
51.0 %
-9
14·10 H
1.0
∞
2.02·10 s
-9
-9
1.81 s
-1
0.0 %
23·10-12 H
57.7·10
0.0 H
H
400·103
-6
23·10
-12
0.0 %
0.0
TypBT
-410·10
0.8 %
H
TypBC
TypBR
-15
-320·10
-15
-640·10
H
0.0 %
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
Acronym of institute: INM
Date: July 2006
Remarks:
Model equation
LX = (LS + ∆LScurrent + δLSdrift + δLST ) ⋅ K ⋅ K C − δLXT
Definition of quantities
quantity
unit
definition
LS
H
certificate value of the reference standard
∆LScurrent
H
correction for the different measurement current of the reference
standard
δLSdrift
H
time drift of the reference standard
δLST
H
correction for the temperature variation of the reference standard
δLXT
H
correction for the temperature variation of the unknown inductance
Kc
correction factor given by systemic effects of the measurement circuit
(finite resolution of the LCR-meter, undesired couplings, variation of
inductance of the measurement cables, etc.)
K
ratio between the indicated value of the unknown inductance and the
indicated value of the reference standard inductor
H
LX
Uncertainty budget
quantity
estimate
inductance of travelling standard
standard
probability
degrees
sensitivity
uncertainty
uncertainty
distribution
of
coefficient
contribution
freedom
ci
ui(L)
Xi
xi
u(xi)
LS
10.00204 mH
0.00015
mH
∆LScurrent
-0.00017 mH
0.00001
δLSdrift
0.00002 mH
δLST
δLXT
∞
1
0.00015
mH
mH rectangular
∞
1
0.00001
mH
0.00015
mH rectangular
∞
1
0.00015
mH
0.00008 mH
0.00001
mH
8
1
0.00001
mH
0.00000 mH
0.00000
mH rectangular
∞
-1
-0.00000
mH
Kc
1.00000
0.00002
triangular
∞
10
mH
0.00016
mH
K
1.000230
0.000001
normal
29
10
mH
0.00001
mH
Lx
10.00427 mH
0.00027
mH
normal
normal
Page 14 of 20
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
Acronym of institute: NCM
Date: September 2006
Remarks:
Model equation
L = (LS + δLD + δLTS ) ⋅ lK ⋅ l − δLT
Definition of quantities
quantity
unit
definition
LS
H
certificate value of the reference standard
δLD
H
time drift of the reference standard
δLTS
H
correction for the temperature variation of the reference standard
δLT
H
correction for the temperature variation of the unknown inductance
lK
correction factor given by systemic effects of the measurement circuit
Ī
ratio between the indicated value of the unknown inductance and the
indicated value of the reference standard inductor
L
H
inductance of travelling standard
Uncertainty budget
quantity
estimate
standard
probability
sensitivity
uncertainty
uncertainty
distribution
coefficient
contribution
ci
ui(L)
Xi
xi
u(xi)
LS
9.9999
mH
1.50E-04
mH
normal
1.0
1.50E-04
mH
δLD
-0.0002
mH
1.16E-04
mH
normal
1.0
1.16E-04
mH
δLTS
3.00E-05
mH
1.73E-05
mH
rectangular
1.0
1.73E-05
mH
δL T
0.0000
mH
3.46E-05
mH
rectangular
-1.0
-3.46E-05
mH
lK
1.000 000
2.45E-06
triangular
10.0000
mH
2.45E-05
mH
Ī
1.00046
5.60E-07
normal
10.0000
mH
5.60E-06
mH
L
10.0044
1.95E-04
mH
mH
Page 15 of 20
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
Appendix B Technical protocol
The original text of the TECHNICAL PROTOCOL below was edited.
TECHNICAL PROTOCOL
EUROMET project 889
EUROMET.EM-K3
Trilateral comparison of a 10 mH inductance standard
June 2006
Page 16 of 20
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
1. Introduction
The comparison is organized within the framework of Phare 2002 Project BG0201.12 “Strengthening
of the National Conformity Assessment System – Technical Assistance for Standardization and
Metrology”, EUROPE Aid/116486/D/SV/BG.
Three national institutes of metrology are taking part in this comparison: PTB (Germany), NCM
(Bulgaria) and INM (Romania).
PTB is responsible for providing the travelling standard and the evaluation of the measurement results.
NCM is responsible for the protocol and the final report.
It is planned to complete this comparison in September 2006.
2. Description of travelling standard
2.1. The travelling standard is an inductance standard having the nominal value of 10 mH. It is
constructed starting from a General Radio 1482-L 10 mH inductance standard, encased in a
thermostated enclosure.
The thermostatic device guarantees a constant operating temperature using a power supply unit.
During the transportation a set of batteries (8 pieces, LR 20 type) or the car’s supply system of 12 volt
(in the case of transportation by car) can be used.
2.2. Specifications
Nominal value of inductance
Relative instability of inductance
Nominal thermostatic temperature
Instability of thermostatic temperature with an instability of
the ambient air temperature of 0.5 K
Dependence of the value of inductance on the ambient air
temperature in the range from 18 °C to 28 °C
Measuring frequency
Measuring voltage at the standard
Effective resistance (DC) of the coil at an ambient air
temperature of 23.0 °C ± 0.1 K
Width of the HIGH and LOW connecting terminals
Connection system
Power supply of thermostat:
• power supply unit (230 V ± 10%; 50 Hz);
• set of batteries (2 x 6 V);
• 12 V supply system of a car
Power cable
Dimensions of leather bag
Total mass
10 mH ± 0.1%
< 1 ppm per year
30.0 °C± 0.2 K
±0.01 K per year
≤ 0.3 ppm per K
1 000 Hz
≤ 0.5 V
№01 – 8.671 Ω
19 mm
Two terminals (case is internally
connected with LOW terminal)
0.5 A at 12 V (DC)
Red plug to be connected to plus,
blue plug to be connected to minus
470 mm x 30 mm x 400 mm
Approx. 38 kg
2.3. Accessories
− Power supply unit;
− Set of batteries (2 pieces);
− 1 adapter cable for connection to a 12 V car supplies system
Page 17 of 20
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
3. Quantities to be measured
−
−
−
−
L: inductance of the standard (two terminals);
R: DC resistance of the inductor coil;
f: measurement frequency;
Text: the temperature (°C) of the environment where the standard is measured.
4. Measurement instructions
4.1. Measurements should be performed under the following conditions:
− Measurement frequency: 1000 Hz;
− Measuring voltage: 0.5 V (rms);
− Temperature of the environment: 23°C ± 1°C;
− Relative humidity: between 30 % and 70 %.
4.2. Set-up of the standard:
Under laboratory conditions the standard is supplied by the power supply unit. The red lamp signals
readiness for operation. The green lamp indicates that the heater of the thermostat is switched on.
In order to avoid electromagnetic interference during inductance measurement, the power supply unit
must be placed as far as 2 meters away from the inductance bridge and may be switched off during
the inductance measurements, but for no longer than 5 minutes.
The participating laboratories are asked to follow the Operating Instructions of the travelling standard.
5. Reporting of results
A report should be sent to the pilot laboratory within one month after the measurements are
completed. The report should include:
– Description of the measurement method;
– The reference standard;
– The traceability to the SI;
– The results of the quantities to be measured (list of section 3);
– The associated standard uncertainties, the effective degrees of freedom and the expanded
uncertainties;
The measurement frequency, the applied voltage and the environment conditions must also be
reported.
6. Uncertainty of measurement
The uncertainty must be calculated following the ISO “Guide to the expression of uncertainty in
measurement” (GUM), 1995 and the complete uncertainty budget must be reported.
Page 18 of 20
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
7. Transportation
The travelling standard must be transported in the travel leather bag and protected from mechanical
loads, vibration etc. A transport box suitable for transport by plane or car is provided. This box is
equipped with tilt and squeeze indicators. It has to be handled carefully and kept the right way up.
The travel box contains the following items:
– leather bag,
– inductance standard,
– power supply unit,
– set of two batteries (6 V lead storage battery, Hoppecke)
with connection cable and fuse,
– spare fuse,
– 1 adapter cable for connection to a 12 V car supply system,
– mechanical temperature recorder (Metrawatt Thermoscript 838012),
– spare strip charts for the temperature recorder (initially 3 coils),
– operating instructions of the travelling standard (this document),
– operating instructions for the temperature recorder
(in German, in case of difficulties consult PTB),
When it is transported by car, the standard must be connected by the adapter cable to the 12 V power
system of the car. Carrying the standard by air or rail requires the connection to the set of batteries.
The batteries have to be charged with an appropriate power supply (not included in the box). Standard
4 mm banana plugs can be used to connect the batteries.
During transport the temperature recorder has to be switched on. If the operation of this recorder has
to be interrupted or if a new strip chart coil is used, the date and time of both the stop and start of
operation have to be written on the paper by hand. The total recording time per coil is about 30 days.
The transport box always has to be carried and kept upright. It internally contains internal eyelets
which shall be used to fix the leather bag inside the box.
Page 19 of 20
EUROMET 889 - EUROMET.EM-K3: 10 mH Inductance Trilateral Comparison
8. Participants
Table 1. List of participants and contact information.
Laboratory address
Contact name, e-mail
Physikalisch-Technische Bundesanstalt
(PTB)
Electricity Division, FB 2.1
Bundesallee 100
38116 Braunschweig
GERMANY
Jürgen Melcher
Juergen.Melcher@ptb.de
National Centre of Metrology (NCM)
52-B G. M. Dimitrov Str.
1797 Sofia
BULGARIA
Petya Aladzhem
ncm@sasm.orbitel.bg
National Institute of Metrology (INM)
sos. Vitan Barzesti 11 sector 4,
042122 Bucuresti
ROMANIA
Anca Nestor
anca.nestor@inm.ro
9. Schedule
Table 2. List of the participants, measurement dates and report dates.
Laboratory
PTB - Germany
INM - Romania
NCM - Bulgaria
PTB - Germany
Measurement dates
April 2006
12 - 29 May 2006
2 - 16 June 2006
July 2006
Page 20 of 20
Report date
June 2006
July 2006