Top Banner
1 The Distributed The Distributed Measurement Systems: a Measurement Systems: a New Challenge New Challenge for the Metrologists for the Metrologists by by Alessandro Ferrero Alessandro Ferrero and Roberto and Roberto Ottoboni Ottoboni Politecnico di Milano – Dipartimento Politecnico di Milano – Dipartimento di Elettrotecnica di Elettrotecnica Milano - Italy Milano - Italy
18

1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Mar 31, 2015

Download

Documents

Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

11

The Distributed Measurement The Distributed Measurement Systems: a New ChallengeSystems: a New Challenge

for the Metrologistsfor the Metrologists

byby

Alessandro FerreroAlessandro Ferrero and Roberto Ottoboni and Roberto OttoboniPolitecnico di Milano – Dipartimento di ElettrotecnicaPolitecnico di Milano – Dipartimento di Elettrotecnica

Milano - ItalyMilano - Italy

Page 2: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 22

OverviewOverview

IntroductionIntroductionEvolution of the Measurement InstrumentsEvolution of the Measurement Instruments

DSP-based architecturesDSP-based architecturesVirtual Instruments (VI)Virtual Instruments (VI)Distributed Measurement Systems (DMS)Distributed Measurement Systems (DMS)

Metrology issuesMetrology issues

Page 3: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 33

Signal processing & MeasurementSignal processing & Measurement

Signal processing is the basis of the Signal processing is the basis of the measurement activitymeasurement activity

Any evolution in signal processing Any evolution in signal processing techniques has a direct impact on techniques has a direct impact on measurement systemsmeasurement systems

Page 4: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 44

Digital Signal ProcessingDigital Signal Processing

Analog signals can be converted into a Analog signals can be converted into a sequence of digital samplessequence of digital samplesThe sampling theorem provides the conditions The sampling theorem provides the conditions

for preserving the information associated with for preserving the information associated with the original analog signalthe original analog signal

The modern instruments are based on The modern instruments are based on DSP techniquesDSP techniques

They have benefited of the recent, They have benefited of the recent, impressive evolution of the DSP impressive evolution of the DSP techniques and devicestechniques and devices

Page 5: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 55

The first revolution:The first revolution:DSP-based instrumentsDSP-based instruments

T&C ADC Mem Comp

Field

Input signalsMeas.

Ana

log

proc

essi

ng

Digital processing

From: A measurement, an instrument

To: A measurement, an algorithm

Page 6: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 66

The second revolution:The second revolution:Virtual InstrumentsVirtual Instruments

T&C ADC Mem Comp

Field

Input signalsMeas.Interf.

An interface is added to:An interface is added to:Provide an instrument-like, user-friendly Front Provide an instrument-like, user-friendly Front

PanelPanelProvide a graphic programming interfaceProvide a graphic programming interface

Page 7: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 77

The third revolution:The third revolution:Distributed Measurement InstrumentsDistributed Measurement Instruments

T&C ADC Mem Comp

Interf.

Net Int.

Field

World

Input signals

An interface to an An interface to an interconnection interconnection network is addednetwork is added

Page 8: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 88

The new paradigmThe new paradigm

The desired measurement result is The desired measurement result is provided by a network of cooperating provided by a network of cooperating instruments that share their resourcesinstruments that share their resources

The desired measurement result is The desired measurement result is provided by a network of provided by a network of cooperatingcooperating instruments that instruments that shareshare their resources their resources

Internet/Intranet

Field

Field

Field

ADC

ADCADC

Measurement unit 1

Measurement unit jMeasurement unit N

Supervising unit

Page 9: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 99

Better performance …Better performance …

……more problems!more problems!The different units share resources and The different units share resources and

datadatacollected under different conditionscollected under different conditionsacquired by different hardware systemsacquired by different hardware systems

The evaluation of the measurement The evaluation of the measurement uncertainty becomes a problem.uncertainty becomes a problem.

Page 10: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 1010

The most mischievous problemThe most mischievous problem

The lack of time synchronization between The lack of time synchronization between the sampling devices of the different units.the sampling devices of the different units.

When measured data are shared across a When measured data are shared across a public-domain network (Internet), the public-domain network (Internet), the transmission time becomes largely transmission time becomes largely unpredictable.unpredictable.

The risk is that the different units start The risk is that the different units start working on different timelines.working on different timelines.

Page 11: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 1111

The lack of synchronizationThe lack of synchronization

The same event is seen at different time The same event is seen at different time instants by the different unitsinstants by the different units

Different delays are introducedDifferent delays are introducedTheir estimation may be cumbersomeTheir estimation may be cumbersome

The consequent uncertainty estimation uselessThe consequent uncertainty estimation useless

Unit 1Unit 1

Event at time Event at time tt11

Unit 2Unit 2

Event at time Event at time tt22

t

t

Page 12: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 1212

The solutionThe solution

Clock synchronizationClock synchronizationA unique timeline is defined for all unitsA unique timeline is defined for all unitsA timestamp can be associated to each A timestamp can be associated to each

transmitted datatransmitted dataMeasurement uncertainty is not related to Measurement uncertainty is not related to

the transmission delay, but to the the transmission delay, but to the residual residual synchronization errorsynchronization error..

Page 13: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 1313

Clock synchronizationClock synchronizationHow accurate?How accurate?As always, it depends on the As always, it depends on the target target

uncertaintyuncertainty..The case of the identification of the origin The case of the identification of the origin

of transient disturbances in the electric of transient disturbances in the electric system.system.

Page 14: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 1414

Measuring unit 1

Measuring unit 2

t0t1t2

t If If tt22 - - tt11 > 0, > 0,

then the disturbance’s origin is upstream then the disturbance’s origin is upstream the measuring unit 1the measuring unit 1

The synchronization uncertainty must be The synchronization uncertainty must be significantly lower than significantly lower than tt22 - - tt11

Page 15: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 1515

Clock synchronizationClock synchronizationHow accurate?How accurate?As always, it depends on the As always, it depends on the target target

uncertaintyuncertainty..The case of the identification of the origin The case of the identification of the origin

of transient disturbances in the electric of transient disturbances in the electric system.system.A GPS synchronization is requiredA GPS synchronization is required

50 ns with respect to UTC50 ns with respect to UTCThe case of the identification of harmonic The case of the identification of harmonic

disturbancesdisturbances

Page 16: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 1616

Each measurement unit measures suitable Each measurement unit measures suitable power quality indices power quality indices averagedaveraged over a over a given intervalgiven interval

The synchronization uncertainty must be The synchronization uncertainty must be significantly lower than the duration of the significantly lower than the duration of the averaging intervalaveraging interval

Load1

Load 2

Load j

Load N

Feeder

Measuring units

Page 17: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 1717

Clock synchronizationClock synchronizationHow accurate?How accurate?As always, it depends on the As always, it depends on the target target

uncertaintyuncertainty..The case of the identification of the origin The case of the identification of the origin

of transient disturbances in the electric of transient disturbances in the electric system.system.A GPS synchronization is requiredA GPS synchronization is required

50 ns with respect to UTC50 ns with respect to UTCThe case of the identification of harmonic The case of the identification of harmonic

disturbancesdisturbancesA NTP synchronization is sufficient (A NTP synchronization is sufficient (10 ms)10 ms)

Page 18: 1 The Distributed Measurement Systems: a New Challenge for the Metrologists by Alessandro Ferrero and Roberto Ottoboni Politecnico di Milano – Dipartimento.

Politecnico di Milano

INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008INGRID 2008 – Lacco Ameno – Ischia – ITALY – April 9-11, 2008 1818

ConclusionsConclusionsDMS benefit of the evolution of the DMS benefit of the evolution of the

interconnection of the computing systems.interconnection of the computing systems.They are the natural evolution of the They are the natural evolution of the

remote measurement systemsremote measurement systemsThey are a promising tool for the solution They are a promising tool for the solution

of very complex measurement tasksof very complex measurement tasksThe present new problems in metrologyThe present new problems in metrology If disregarded they may lead to largely If disregarded they may lead to largely

incorrect resultsincorrect results