Athens programme 2008
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Athens Programme 2008. Athens Programme 2008. Metrology of Electrical Quantities. Laboratory of Legal Metrology Department of Measurements Faculty of Electrical Engineering Czech Technical University in Prague Responsible professor: Prof. Ing. Jaroslav Bohacek, DrSc. Phone +420 22435 2220

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Athens programme 2008

Athens Programme2008

Athens Programme2008

Metrology of Electrical Quantities

Laboratory of Legal Metrology

Department of Measurements

Faculty of Electrical Engineering

Czech Technical University in Prague

Responsible professor:

Prof. Ing. Jaroslav Bohacek, DrSc.

Phone +420 22435 2220

E-mail [email protected]

http://measure.feld.cvut.cz/...


William thomson lord kelvin

William Thomson, Lord Kelvin

I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it …

… but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind.


Brian w petley

Brian W. Petley

Far from being a dull area of science, high-precision measurements are an increasingly exciting area in which to work, for they push theory and experiment to the very limits of which they are capable…

If we recall that the rich oil deposits under the North Sea remained unknown until the advent of the very precise geophysical measurements, or that the spin of the electron was inferred from precise spectroscopic measurements, we see more clearly the class of discoveries which can come from precise measurement.


Athens programme 2008

Laboratory

visits

Course

objectives

Lectures

What is

metrology?

Previous

intro

Laboratory

demonstrations

Please, select some topic above to continue


Laboratory demonstrations

Laboratory demonstrations

  • Thompson-Lampard's capacitance standard

  • Frequency performance of  resistance standards

  • Calibration of capacitance boxes


Course objectives

Course objectives:

  • to present an overview of modern and perspective methods for precision measurements of electrical quantities,

  • to demonstrate various techniques used in calibrations of electrical measurement instruments and standards.


L ectures

Lectures

  • Lecture 1

  • Introduction

  • Measurement units and measurement standards

  • Quantum standards of voltage and resistance

  • Thompson-Lampard's capacitance standard

  • Equivalent circuits of standard resistors, capacitors and inductors

  • Resistors with calculable frequency performance

  • Transfer standards


L ectures1

Lectures

  • Lecture 2

  • Voltage and current inductive ratio devices and optimization of their metrological parameters.


L ectures2

Lectures

  • Lecture 3

  • Methods for precision measurement of dc current and dc voltage

  • Modern potentiometers

  • Measurement of voltage, power and energy in audiofrequency range

Sample

lecture


L ectures3

Lectures

  • Lecture 4

  • Bridges for dc and ac measurements of resistance

  • Transformer and current-comparator-based capacitance bridges

  • Metrological applications of the quantum Hall effect (QHE)


What is metrology

What is Metrology?

Metrology is the science of measurement.


What is metrology1

What is Metrology?

Metrology covers three main activities:

  • The definitionof internationally accepted units of measurement, e.g. the metre.

  • The realizationof units of measurement by scientificmethods, e.g. the realizationof a metre through the use of lasers.

  • The establishment of traceabilitychains by determining and documenting the value and accuracy of a measurement and disseminating that knowledge, e.g. the documented relationship between the micrometer screw in a precision engineering workshop and a primary laboratory for optical length metrology.


What is metrology2

What is Metrology?

Metrology is considered in three categories with different levels of complexity and accuracy:

  • Scientific metrologydeals with the organisation and development of measurementstandards and with their maintenance (highest level).

  • Industrial metrologyhas to ensure the adequate functioning of measurementinstruments used in industry as well as in production and testing processes.

  • Legal metrologyis concerned with measurements where these influence thetransparency of economic transactions, health and safety.


Athens programme 2008

Systematic measurement with known degrees of uncertainty is one of the foundations of industrial quality control and, generally speaking, in most modern industries the costs bound up in taking measurements constitute 10 -15% of production costs.


Laboratory visits

Laboratory visits:

  • Czech Metrology Institue

  • www.cmi.cz

  • Calibration of digital multimeters

  • Quantum Hall effect based calibrations of resistance standards


  • See you in prague

    Laboratory of Legal Metrology, CTU Prague

    Athens 2006

    See you in Prague!


    Athens programme 2008

    TOPIC 3


    Current balance

    C1

    C2

    IC1 = IC2 = IC3 = I

    C3

    Current balance

    IC1 enters C1 at the bottom and leaves it at the top,

    IC2 enters C2 at the top and leaves it at the bottom. 

     Electromagnetic forces on the suspended coil, produced by these two currents, are of the same sense.


    Current balance1

    Current balance


    Current balance2

    Current balance


    Current balance operation

    Current balance operation

    • The mass of the suspended coil plus the vertical electromagnetic force exerted on it are counterbalanced by means of a mass m on the left scale pan.

    • After reversing the current in the suspended coil, the change m of this mass, necessary to offset the change F of the acting electromagnetic force, is determined.


    Current balance operation1

    Current balance operation

    A separate moving experiment makes it possible to avoid the troublesome calculation of f from the dimensions of the coils:

    Coil C3, which is threaded by the magnetic flux produced by the current I flowing in C1 and C2, is moved with a constant velocity v in the vertical direction, a voltage u(t) being induced in it:


    Current balance operation2

    Current balance operation

    If a voltage drop U = R I isproduced by the current I on a known resistance R and if a velocity v is choosen for which

    in the moment of passage of the scale beam through its equilibrium position,


    Electronic kilogram

    Electronic kilogram

    In case that quantum standards of voltage and resistance are used to measure the current I flowing in the coils in course of the weighing experiment, a current balance with a known value of f can be used to produce known values of electromagnetic force and to monitor variations of masses which are used to counterbalance it.


    Voltage balance

    Voltage balance

    is an apparatus based on counterbalancing the attractive force between electrodes of a capacitor.


    Dc comparator potentiometer

    Is

    Ip

    Constant

    current

    PS

    Slave

    PS

    R

    Ux, Ue

    Ns

    ns

    Np

    PD

    Ns = 1000 turns

    OSC

    ns =  11 turns

    in steps of

    10-4 turns

    Np 2000 turns,

    steps of 10-4 turns

    DC comparator potentiometer


    Realization of the equivalent of fractional turns

    SPS

    Is

    ...

    500

    50

    Ω

    Ω

    5.625 Ω

    1turn/step

    R

    1000 turns

    Realization of the equivalentof fractional turns


    Primary voltage standard system with closed cycle refrigerator

    Primary voltage standard system with closed-cycle refrigerator


    Primary voltage standard system with closed cycle refrigerator1

    Primary voltage standard system with closed-cycle refrigerator

    • 100 nV calibration accuracy

    • -11 V to 11 V range available from 10-V system

    • typically 1 hour stability time at 10 V for 10-V system

    • automatic voltage calibration in minutes

    • automatic calibration of DVMs

    • complete system diagnostics


    Rms dc thermocouple comparator

    1

    2

    S1

    S2

    Rs1

    Rs2

    Ux

    Ur

    TE1

    R

    TE2

    RMS/DC thermocouple comparator


    Automatic rms dc thermocouple comparator

    Ux

    Ur

    Rs1

    Rs2

    TE1

    TE2

    Automatic RMS/DC thermocouple comparator


    Thermocouple protection

    to relay R

    drives

    A

    R

    R

    to relay R

    drives

    A

    Thermocouple protection


    Rms dc thermistor comparator

    Ua

    R1

    R2

    Ur

    A

    Rs1

    T1

    T2

    Ux

    Rs2

    RMS/DC thermistor comparator


    Improved rms dc thermistor comparator

    Ua

    R1

    R3

    R2

    Ur

    A1

    A2

    Rs1

    Rs2

    Ux

    R4

    T1

    T2

    Improved RMS/DC thermistor comparator


    Electrodynamic method of measurement of ac power

    moving

    coil

    ic1

    ic1

    ic2

    fixed coils

    Electrodynamic method of measurement of AC power

    ic1=i1 + I1

    ic2=i2 - I2


    Electrodynamic method of measurement of ac power1

    Uout

    Ur

    I1

    I2

    Control

    circuit

    R

    R

    ic1

    ic2

    electrodynamometer

    R

    R

    uI

    uU

    i2

    i1

    A2

    A1

    fixed coils

    moving coil

    Electrodynamic method of measurement of AC power

    i1


    Thermal wattmeter

    uU

    Uout

    R

    R

    R

    R

    A4

    A2

    A1

    R

    R

    R

    R

    uI

    A3

    Thermal wattmeter


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