To learn and understand different types of measurements units, measurement constants, calibration and measurement standards as well as principles and practices of treaceability.

1. Welcome!
PRINCIPLES AND PRACTICES
OF TRACEABILITY AND
CALIBRATION
1
By:
Jasmin NUHIC

2. OBJECTIVE
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• To learn and understand different types of
measurements units, measurement
constants, calibration and measurement
standards as well as principles and
practices of treaceability.

3. AGENDA
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• Introduction
• Base SI Units
• Derived SI Units
• SI Multipliers and Conversions
• Fundamental Constants
• Common Measurements
• Principles and Practices of Traceability
• Types of Measurement Standards
• Substitution of Calibration Standards
• Sample Questions
• Q & A Session

4. BASE SI UNITS
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Characteristic Fundamental
Unit
Description
Length Meter (m) Path of light traveling in vacuum during
1/299,792,458 of a second
Time Second (s) Duration of 9,192,631,770 periods of
radiation corresponding to the
transition between two hyperfine levels
of ground state of the cesium atom
Mass Kilogram (kg) Equal to international prototype
platinum-iridium alloy cylinder
Electric Current Ampere (A) Constant flow that produces 2X10^-7
Newtons per each meter of length
between two straight conductors

6. BASE SI UNITS (cont’d)
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Characteristic Fundamental Unit Description
Temperature Kelvin (K) Fraction of 1/273.16 of the
thermodynamic temperature of the
triple point of water (0.01 C)
NOTE: know how to convert from
Kelvin to Celsius and vice-versa
Light Candela (cd) Luminous intensity of a source that
emits monochromatic radiation of
frequency 540x10^12 hertz and has
radiant intensity in the same direction
of 1/683 watt
Amount of Substance Mole (mol) Amount of substance of a system
which contains many elementary
entities as there are atoms in 0.012
kilogram of carbon 12

7. DERIVED SI UNITS
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Characteristic Fundamental Unit Description
Area m^2 Length multiplied by length
Volume m^3 Length multiplied by length multiplied
by length
Frequency Hz Time inverted
Density kg / m^3 Mass divided by volume
Velocity m / s Length divided by time
Acceleration m / s^2 Length divided by squared time
Force N Mass multiplied by acceleration

8. DERIVED SI UNITS (cont’d)
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Characteristic Fundamental Unit Description
Pressure Pa Newton divided by volume
Kinematic Viscosity m^2 / s Squared length divided by time
Work (energy) J Newton multiplied by length
Power W Power divided by time
Electric Charge C Amperes multiplied by time
Voltage
(electromotive force)
V Power divided by amperes
Electric Resistant Ω Voltage divided by amperes

9. DERIVED SI UNITS (cont’d)
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Characteristic Fundamental Unit Description
Electric Capacitance F Amperes multiplied by time divided by
voltage
Magnetic Flux Wb Voltage multiplied by time
Inductance H Voltage multiplied by time divided by
amperes
Magnetic Flux Density T Magnetic flux divided by area
Magnetic Field
Strength
A/m Amperes divided by length
Magnetomotive Force A Amperes
Luminance cd / m^2 Candela divided by area

10. DERIVED SI UNITS (cont’d)
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Characteristic Fundamental Unit Description
Luminance flux Im Candela multiplied
Illuminations Lx Luminance flux divided by area

11. SI MULTIPLIERS
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12. FUNDAMENTAL CONSTANTS
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 Speed of light in vacuum;
unchanging in space or time
 Not dependent on time or
place; gravitational attraction
of matter
 Varies by place; within the US,
it varies 0.2% (scales should be
calibrated at point of use)
 Relationship between
pressure, volume and
temperature in an ideal gas
 Relationship between amount of
substance and number of molecules in
that amount
 Back body used in calibration; temp
of black body measured by its color

13. COMMON MEASUREMENTS
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• Inspection, Measurement, and Test
Equipment (IM&TE)
• To calibrate any equipment, it is necessary to
generate a known amount of the variable to be
measured and apply it to the unit under test.
• Variable can be generated by using known generator
(i.e. gage block) or unknown generator (in the case it
must be measured simultaneously with calibrated
device).
• Where IM&TE is also a generator then the output
must be known.

14. COMMON MEASUREMENTS (cont’d)
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• Laboratory Measurement of Temperature:
– Liquid-in-glass thermometers must be immersed in the
calibration bath to a predefined depth.
– Resistance-Temperature-Devices work on the basis of
temperature versus resistance characteristics.
– Thermocouples work the basis of temperature versus
voltage characteristics.
– Optical Pyrometer is used to measure temperatures above
200 C by measuring the color of the object from the
distance.

15. COMMON MEASUREMENTS (cont’d)
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• Laboratory Measurement of Humidity:
– Humidity is best measured using a chilled mirror
hydrometer.
– Psychrometer measures humidity by comparing
the temperature near a dry bulb with that of a wet
bulb (the lower the humidity the greater the
cooling)

16. COMMON MEASUREMENTS (cont’d)
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• Laboratory Measurement of Pressure:
– The most accurate way to measure pressure is to
generate it (weight divided by the area).
– Low pressures can be measured using manometer
(column of liquid responds to positive and
negative pressures).
– The Bourdon gage measures pressure by
mechanical means of elasticity (elastic element
used).
– The Quartz Bourdon gage measures pressure by
means of electronic transducer.

17. COMMON MEASUREMENTS (cont’d)
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• Laboratory
Measurement of Torque:
– Torque is difficult to
generate and measure.
– Greatest uncertainty,
when it comes to
measuring torque, is the
distance from the center
of the mass to the center
of the ratating lever arm.

18. COMMON MEASUREMENTS (cont’d)
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• Laboratory Measurement
of Force:
– Force is generate by hanging
calibrated weights on the
unit under test (requires
correction to local gravity).

19. COMMON MEASUREMENTS (cont’d)
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• Laboratory Measurement of
Mass:
– Masses are calibrated by
comparison to known and
traceable reference standards.
– Gravity correction
required?????
• No, if the materials of the
standard are the same as of the
unit under test.
• Yes, where there is difference in
materials.

20. COMMON MEASUREMENTS (cont’d)
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• Laboratory Measurement of Electrical
Quantity:
– Electronic Calibrators, Capacitors and
Inductors, Digital Multimeters, Null
Indicators, Bridges and Transfer Standards.
– Number of digits on the display does NOT mean
that the same level of accuracy has been
achieved.
– In case where DC is used, special attention should
be paid to high and low voltage (potential results
distortion)

21. COMMON MEASUREMENTS (cont’d)
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• Laboratory Measurement of Electrical
Calculations:
– Calibration technician is expected to perform
simple calculations when it comes to electronics
and their properties.
– Electric Current is measured in amperes
– Electronic Potential or electromotive force is
measured in volts
– Electrical resistance is measured in ohms next
slide
– Electrical Power is measured in Watts

22. COMMON MEASUREMENTS (cont’d)
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• Ohm’s Law:
E = iR or i = E/R or R = E/I
R – resistance
i – current
E – voltage

23. COMMON MEASUREMENTS (cont’d)
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• Laboratory Measurement of Time and
Frequency:
– GPS (Global Positioning System) signal is
considered traceable to national standards and
has output of about 10MHz (at full capacity).
When it comes to length measurements, the most
important fact to remember is that the temperature for
dimensional measurements shall be 20 C!

24. PRINCIPLES AND PRACTICES OF TRACEABILITY
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• Traceability is defined as ability to link the results of
the calibration and measurement to related standard
and/or reference (preferably national or international
standard) through an unbroken chain of
comparisons.
• Calibration is typically performed by measuring a test
unit against a known standard or reference.
• Master standard (i.e. gages) are kept by National
Measurement Institute (NMI) of each country.

25. PRINCIPLES AND PRACTICES OF TRACEABILITY (cont’d)
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• National Institute of Standards and Technology (NIST)
provides internal tracking numbers, which are often
used as evidence of traceability.
• WARNING! NIST does not certify or guarantee that
calibration and measurements are correct, nor does
it provide any kind of certification of accuracy and
calibration and the internal number does mean that
the test unit calibrated is indeed valid. NIST only
provides certifications for the work performed by
them.

26. TYPES OF MEASUREMENT STANDARDS
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27. TYPES OF MEASUREMENT STANDARDS (cont’d)
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• International Standard
– Highest level of reference standards agreed by multiple
countries for the common purpose (kept at Bureau of
Weights and Measures in Sevres, France).
• Intrinsic Standard
– If properly maintained they provide standards based on
laws of physics, fundamentals of nature, invariant
properties of materials.
• National Standard
– In US, it is maintained by NIST, and it is a standard formed
by one or many groups within one country (or only few
countries = adapted).

28. TYPES OF MEASUREMENT STANDARDS (cont’d)
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• Reference Standard
– Item of highest metrological quality located at a site where
calibration is being conducted.
• Master Standard
– Lower level of Reference Standard and used for calibration
of lower level calibration requirements measuring devices.
• Working Standard (working master)
– Should be compared to Master Standard or Reference
Standard on regular basis; Used for daily checks /
comparisons of the calibrated devices.

29. TYPES OF MEASUREMENT STANDARDS (cont’d)
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• Derived Standard
– Combination of two or more standards for the sake of fulfilling
traceability requirements.
• Consensus Standard
– Example of such standard is Rockwell Hardness; This standard is used
when no traceability to a known standard can be established, but
rather an agreement of all parties is considered the standard.
• Transfer Standard
– This standard is actually an artifact designed to be calibrated at one
location and transferred to another location without its impact to
validity of calibration (deviation ranges due to transportations
acceptable).
– NOTE: Sometimes Transfer Standard is used to describe transferring
values from a NIST standard to a local standard.

30. SUBSTITUTE OF CALIBRATION STANDARDS
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• When no valid standard is available at point of use, a
technician can:
– Postpone the calibration until the standard becomes
available, or
– Identify suitable substitute standard
• If substitute standard is to be used then:
– Procedure must allow it
– Substitute standard must be available at point of use
– Substitute standard must be of equal or better
specifications
– The uncertainty of standard must be equal or better than
required to calibrated the test unit

31. SUBSTITUTE OF CALIBRATION STANDARDS (cont’d)
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• ISO standard for calibration laboratories is:
– ISO 17025
– This standard is NOT procedure heavy
• ANSI standard for calibration is:
– ANSI Z540-1
Remember: Not all procedures and practices allow substitutions of standards
and sometimes they might be test unit specific
Remember: Substitution is a “judgment call” made by a technician (where no
documented procedure and/or practice exists)

32. THANK YOU!
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Presented By:
Jasmin NUHIC