Fluke Digital Multimeter Use and care manual

©Fluke Calibration 2011 Basics Of Measurement Uncertainty for DMM Calibration 1
Applying Measurement Uncertainty To
Digital Multimeter Calibration
An introductory study of measurement
uncertainty and its application to digital
multimeter calibration
Teleconference:
US & Canada Toll Free Dial-In Number: 1-[phone]
International Dial-In Number:[phone]
Conference Code: 1010759559

©Fluke Calibration 2011 Basics Of Measurement Uncertainty for DMM Calibration 2
Welcome
Greetings from –
Fluke Corporation
Everett, Washington, USA
We are very pleased to bring you this
presentation on measurement
uncertainty for DMM Calibration.

©Fluke Calibration 2011 Basics Of Measurement Uncertainty for DMM Calibration 3
Welcome
This presentation is based on Fluke’s
extensive experience with:
−Use and design of calibration
Instruments
−Our experience and understanding of the
problems faced when applying
measurement uncertainty for both
regular and accredited metrology
Thanks for your time, we hope you find it
both valuable and useful.
Welcome and Thanks!

©Fluke Calibration 2011 Basics Of Measurement Uncertainty for DMM Calibration 4
Presented by
Fluke’s Calibration Business Unit
and Jack Somppi
Electrical Calibration Instruments
Product Line Manager
[e-mail]

©Fluke Calibration 2011 Basics Of Measurement Uncertainty for DMM Calibration 5
Web seminar etiquette
•Choice of Audio –VOIP or Teleconference
−VOIP receives audio only while teleconference is two way
sound
• Don’t mute your phone if you have background
music enabled
•Use Q&A or chat to send me questions or request
clarification
•There will be an opportunity throughout the
discussion to pause and ask questions.
•You can view the material using either full screen
or multi window methods

©Fluke Calibration 2011 Basics Of Measurement Uncertainty for DMM Calibration 6
Applying Measurement Uncertainty To
Digital Multimeter Calibration
An introductory study of measurement
uncertainty and its application to digital
multimeter calibration

©Fluke Calibration 2011 Basics Of Measurement Uncertainty for DMM Calibration 7
Objectives
In this session you will -
•Be introduced to the concept of measurement
uncertainty and why it is important
•Observe the basic elements that influence
measurement uncertainty for DMM calibration
applications
•Study a simple but detailed example of calculating
measurement uncertainty
•Consider some benefits of automating measurement
uncertainty calculations
•Receive a variety of references for further research on
this topic

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Benefits
•Introduce measurement uncertainty to
those in calibration/metrology who are
not familiar with it
•Understand why measurement
uncertainty is important for quality
metrology
•Understand measurement uncertainty
with respect to DMM calibration
•Appreciate to the benefits of automation
•Have technical references for more
detailed information
•Obtain copies of this presentation via
email

©Fluke Calibration 2011 Basics Of Measurement Uncertainty for DMM Calibration 9
Measurement Uncertainty
& Why It Is Important

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Facts regarding measurement -
•Can you ever measure the true value of
something?
−No, there will always be errors
•How important is this fact?
−Very important, as measurement is never complete
unless you know how good it is!
• How is this taken into account in today’s
calibration & metrology?
−By applying & documenting the measurement uncertainty
process to the tests being done

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Measurement uncertainty in
metrology today…
Measurement errors were not rigorously evaluated in all
cases. Often in industrial labs, accuracy ratio analysis
(referred to as TUR’s or TAR’s or TSR’s) had been frequently
used to evaluate the significance of the calibrator’s errors on
the measurements. Other errors were sometimes ignored.
Individually analyzed, calculated, & documented measurement
uncertainties are more thorough and are required to be
considered - as stated in
−ANSI/ISO/IEC 17025:2005 General Requirements for the
Competence of Testing and Calibration Laboratories

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ISO 17025 –
about measurement uncertainty…
5.4.6 Estimation of uncertainty of
measurement
−5.4.6.1 A calibration laboratory, or a testing
laboratory performing its own calibrations, shall
have and shall apply a procedure to estimate the
uncertainty of measurement for all calibrations
and types of calibrations.

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… about the sources of
uncertainty…
ISO 17025, Section 5.4.6.3:
−NOTE 1: Sources contributing to the uncertainty
include, but are not necessarily limited to,
•The reference standards and reference
materials used
•Methods and equipment used
•Environmental conditions
•Properties and condition of the item being
tested or calibrated
•Operator
There are many contributors to uncertainty

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ISO 17025, Section 5.10.4
Calibration Certificates shall include …
for the interpretation of calibration results
a. The conditions of the test
b. The uncertainty of measurement &
compliance statements to metrological standards
c. Evidence of traceability
When statements of compliance are made, the
uncertainty of measurement shall be taken into account
…about calibration certificates…

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An example of an accredited
calibration certificate –
“Measurement uncertainties at the
time of test are given in the following
pages, where applicable. They are
calculated in accordance with the
method described in NIST TN1297,
for a confidence level of 95% using a
coverage factor of approximately 2
(K=2).”

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To summarize the importance of
measurement uncertainty….
From the NPL UK - “A Beginner's Guide to
Uncertainty of Measurement”
•Uncertainty of a measurement tells us something about
its quality
•Uncertainty of measurement is the doubt that exists
about the results of any measurement
•For every measurement –even the most careful –there
is always a margin of doubt
•You need to know the uncertainty before you can
decide whether the tolerance is met

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“How is this Measurement Uncertainty
obtained?”

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Properly Calculating Measurement
Uncertainty –a topic often discussed &
debated among metrologists
Initially, there were no standardized
process to quantify measurement
uncertainty….
But a standard technique was agreed
upon & published in October 1993:
ISO Guide 98 - Guide to the
Expression of Uncertainty in
Measurement (a.k.a. GUM)

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In the USA, refer to one of the Guides
relating to expressing of Uncertainty in
Measurement
ANSI/NCSL Z540.2-1997 (R2002) U.S.
Guide to Expression of Uncertainty in
Measurement
http://www.ncsli.org and find it in the store
under NCSLI publications
NIST Technical Note 1297
http://www.physics.nist.gov/Pubs/guidelines/
contents.html
Recommendation:
Refer to the GUMs -
Internationally, many metrology
organizations publish similar GUMs

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Questions?
- about measurement uncertainty
or why it is important