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Glossary
Metrology of high-voltage measurands
Terms and symbols
A B C
A
Accreditation
Third-party confirmation that formally sets out that a conformity assessment body has the competence to carry out certain conformity assessment tasks.
DIN EN ISO/IEC 17011
Accreditation body
According to Regulation (EU) 765/2008, the accreditation system in Germany was changed on 1 January 2010. The
German Accreditation Body
(Deutsche Akkreditierungsstelle GmbH) carries out the accreditations.
DAkkS
B
Best measurement capability
The smallest measurement uncertainty that can be stated is the measurement uncertainty stated in the attachment of the accreditation certificate; this can be certified by an accredited calibration laboratory in the calibration certificate if required. A calibration laboratory cannot certify a smaller measurement uncertainty than the measurement uncertainty certified as the smallest measurement uncertainty that can be stated for relevant measuring ranges and measurands.
BIPM
Bureau international des poids et mesures
International Bureau of Weights and Measures. The highest metrological institution worldwide; responsible for looking after the international standards of the SI system of units. For example, the JCGM working group is part of BIPM and manages the Guide to the Expression of Uncertainty in Measurement (GUM) and the International Vocabulary of Metrology (VIM).
BIPM
C
Calibration
Calibration is a process that is used to define metrological properties of a measuring system or measuring instrument. Firstly, the relationships between quantitative variables are established under defined conditions with a measurement uncertainty established via the reference standard.
Secondly, rules are defined according to which the measurement results are obtained from the displayed values.
VIM
Certificate
A written document in paper or electronic form containing the results of a calibration.
Coverage factor
k
Factor used to expand the confidence interval in order to ensure a normal distribution of the measured values. A coverage factor of
k
= 2 should generally be applied to calibration certificates. The value depends on the effective degrees of freedom of the measurement uncertainty calculation.
D E F
D
DAkkS
Deutsche Akkreditierungsstelle GmbH
This is the national accreditation body of Germany (German Accreditation Body, DAkkS). It acts in accordance with Regulation (EU) 765/2008 and the German Accreditation Body Act (Akkreditierungsstellengesetz, AkkStelleG) in the public interest as the sole service provider for accreditation in Germany.
DAkkS-Webpage
Degree of freedom, effective
The degree of freedom is calculated using the Welch-Satterthwaite equation. The coverage factor k is determined from the number of degrees of freedom.
DKD
Deutscher Kalibrierdienst (German Calibration Service)
Technical committee of calibration laboratories under the patronage of Physikalisch-Technische Bundesanstalt,
PTB
. The accreditation tasks in the field of metrology were transferred to
DAkkS
at the start of 2010.
DKD-Webpage
E
EA
European co-operation for Accreditation
European association of national accreditation authorities.
EA-Webpage
Estimated value
An estimated value is the value of a measurand obtained via measurement with a real measuring instrument (subject to a measurement uncertainty due to losses, environmental influences, temperature etc.).
F
G H I
G
GUM
Guide to the Expression of Uncertainty in Measurement
full name of the document JCGM 100.
see JCGM 100
H
I
I -
electric current
In the case of AC current, this is used to describe the RMS value (or effective value) of the current.
Î-
Peak value of the measurand 'current'
An important measurand particularly for impulse currents and AC current.
IAF
International Accreditation Forum
International association for the conformity of accreditation bodies; its task is to prepare the
Mutual Recognition Arrangement (MRA).
IAF-Webpage
ILAC
International Laboratory Accreditation Cooperation
International association of accreditation bodies for laboratories and inspection agencies
ILAC-Webpage
~ MRA
Mutual Recognition Arrangement
International mutual recognition arrangement between MRA signatories.
ILAC-Webpage
ISO/IEC 17025
General requirements for the competence of testing and calibration laboratories
Actually valid issue from 2005. General requirements for the competence of testing and calibration laboratories
J K L
J
JCGM
Joint Committee for Guides in Metrology
A metrological organisation located within BIPM and responsible for publication of metrological documents, for example JCGM 100 and JCGM 200.
JCGM-Webpage
JCGM 100
Guide to the Expression of Uncertainty in Measurement
Fundamental document on the calculation of measurement uncertainty.
JCGM-Webpage
JCGM 100 S1
Guide to the Expression of Uncertainty in Measurement, Supplement 1
Supplement to the JCGM 100 document. The document provides practical examples that show measurement uncertainty is calculated during a measurement.
JCGM-Webpage
JCGM 200
International Vocabulary of Metrology
The International Vocabulary of Metrology defines all of the technical terms used in metrology. The glossary is regularly updated and published. It is available in English and French and can either be downloaded as a PDF file or accessed in its online version via the website of the JCGM committee.
JCGM-Webpage
K
k
-factor
See 'coverage factor
k
'
L
M N O
M
Measurement uncertainty
The measurement uncertainty (sometimes incorrectly referred to as the measuring error) of a measurement is an indicator of inadequacies in a measurement process. It expresses the extent to which a measured value differs from the
true value
.
~, expanded
The combined measurement uncertainty multiplied by the coverage factor
k
.
~, combined
The measurement uncertainty is calculated from individual measurement uncertainty contributions, which are combined using the error propagation law.
Measurement uncertainty contribution
The magnitude of a measurand, measurement process, measurement condition etc. that contributes to the measurement uncertainty. The combined measurement uncertainty is calculated by adding the measurement uncertainty contributions in accordance with the error propagation law.
N
O
Office of weights and measures
Official authority that performs official verification, which is a sovereign task of the state.
Official verification
Test to determine whether or not the measurement uncertainty of a measuring system is within the prescribed limits. Official verification is performed by Physikalisch-Technische Bundesanstalt, ( PTB), national offices of weights and measures or by state-certified examining bodies. Not to be confused with calibration.
P Q R S
P
P -
Active power
The active power component of AC power is the real part of the complex apparent power S. This component of electric power describes the energy consumption and expresses itself in the form of mechanical work, heat or similar.
Performace check
A performance check is a form of control measurement, It is a simplified calibration that is used to verify the metrological properties of a measuring system or measuring instrument. These control measurements are referred to as a
performance check in the relevant standards
.
Performace test
See 'Calibration'
Q
Q -
Reactive power
The reactive power of AC power is the imaginary part of the complex apparent power
S
and describes the energy required to generate an electric or magnetic field in an object (in a capacitor, motor etc.).
R
Reference standard
Physical embodiment of a physical measurand with a defined magnitude and measurement uncertainty, which acts as a reference.
S
S
- Apparent power
The apparent power of AC power is a quantity that is obtained by multiplying the AC current
I
that flows through an an object with the voltage drop
U
across the object. The apparent power is not the same as the consumption of the object. Apparent power is made up of effective power
P
and reactive power
Q
.
T U V
T
Traceability
The process of 'tracing back' is the performance of a comparison measurement between the object under calibration and the international reference standard. The comparison can be performed in two ways:
- directly, by performing a comparison measurement against the international reference standard; or
- indirectly via a transfer standard that has already been traced back . The transfer standard can, itself, be traced back directly or indirectly. The key factor in the process of tracing back is establishing an uninterrupted chain of traced-back comparison measurements between the object under calibration and the international reference standard.
True value
The physically correct value of a measurand that is measured in an ideal case.
U
U -
Electric voltage
In the case of AC voltages, this describes the RMS (effective) value.
Û -
Peak value of the measurand 'voltage'
This is an important measurand, particularly for impulse voltages and AC voltages. The designations
U
p or
U
m are also used.
V
VIM
International Vocabulary of Metrology see JCGM 200.
Webpage VIM
W X Y Z
W
Welch–Satterthwaite equation
Statistical equation for calculating the effective degrees of freedom of a measurement uncertainty calculation. The result of the equation enables the choice of the coverage factor
k
. With the aid of the coverage factor it is possible to calculate the expanded measurement uncertainty from the combined measurement uncertainty.
See
JCGM 100
or
DAkkS-DKD-3
X
Y
Y-circuit
Circuit for implementation of a comparison measurement on high-voltage systems
Z
Calibration
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+49 351 8425 225
Fax
+49 351 8425 9225
E-mail
calibration@highvolt.de
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+49 351 8425 880
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+49 351 8425 9880
E-mail
aftersales@highvolt.com
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+49 351 8425 800
E-mail
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