Metrology: The fabric of science and technology

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Metrology The fabric of science and technology
Lafe Spietz TMA class of 1990
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What is metrology?
The science of measurement(not weather!)
Metrology establishes the international standards
for measurement used by all countries in the
world in both science and industry
Examples distance, time, mass, temperature,
voltage, values of physical and chemical constants
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Why is metrology importantand interesting?

• Standard units and values of constants needed
  for all science Technological standards make
  all technology work better and can save lives
  fire hydrant standards Measurement of constants
  can give fundamental insights into the universe
  drift of fine structure constant

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Who does metrology?
Government labs around the world.
From Article I, section 8 of the U.S Constitution
The Congress shall have Power To fix the
Standard of Weights and Measures
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SI The International System of Units
Lots of derived units
Seven base units
Area m2
Length meter (m)
Speed m/s
Mass kilogram (kg)
Force 1 newton 1 kgm/s2
Time second (s)
Voltage 1 volt 1 m2kg/s3A
Electric current ampere (A)
Frequency 1 hertz 1/s
Thermodynamic temperature kelvin (K)
Power 1 watt 1 kgm2/s3
Electric Charge 1 C 1 As
Amount of substance mole (mol)
Luminous intensity candela (cd)
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Hierarchy of units
Kings and queens of units Time, frequency,
distanceDukes and Earls Current, voltage,
resistancePeasants Mass, temperature,
pressure, luminosity
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Clocks Atomic time
One part per quadrillion accuracy!!!
Accurate frequency gives accurate distance and
time.
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Artifact vs. quantum standards
The modern meter
A metal bar1889-1960
The meter is the length of the path traveled by
light in vacuum during a time interval of
1/299,792,458 of a second
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The story of mass I the modern kilogram
The SI kilogram drifts!
http//www.bipm.fr
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The story of mass II possible replacements
Goal 10 parts per billion accuracy
Avogadros numberMeasurementRoundest object in
the world!
Watt-balance
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Temperature Kelvin, Celsius, and Fahrenheit
294 K
Room temperature
70 F
21 C
273.15 K
32 F
0 C
Water freezes
77 K
-321 F
-196 C
Air liquefies
Helium liquefies
4.2 K
-452 F
-269 C
0 K
-459.67 F
-273.15 C
Absolute zero
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The kelvin the SI unit
The kelvin, unit of thermodynamic temperature, is
the fraction 1/273.16 of the thermodynamic
temperature of the triple point of water.
(0.006 atm)
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ITS-90 the practical realization of the kelvin
PVNkBT
Constant volume gas thermometer
Platinum resistance standard
Not primary!!!
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PLTS-2000 the low temperature definition of the
kelvin
Not primary, and very hard!!
Helium-3 melting pressure thermometer
Superconducting fixed points
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Electrical noise and temperatureThe basic idea
All resistors make electrical noise proportional
to temperature hissing of a radio
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Electrical noise and temperatureapplications of
noise thermometry
By measuring the electrical noise of antennas
pointed towards space, astronomers can measure
the background temperature of the universe!
(images courtesy ofNASA/WMAP Science Team)
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Why noise thermometry is hard
Amplifiers add noise, and have complex behavior
Must be calibrated accurately to measure
temperature accurately
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The Shot Noise Thermometer
P

V
Relates temperature to voltage, Simplifying
amplifier calibration.
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The Shot Noise Thermometer
A new practical low temperature thermometer
Copper Tubing for DC lines
Copper Plumbing parts
Tunnel Junction
SMA Connectors for RF
Built-in Bias Tee (on-board SMT Components)
Total cost of package lt10