Towards an Electronic Towards an Electronic KilogramKilogram

Physics 250Physics 250Victor AcostaVictor Acosta

NOTE: Almost everything in this report was taken from NIST NOTE: Almost everything in this report was taken from NIST websites.websites.

The Old Standard: "Le Gran K"The Old Standard: "Le Gran K"

• Held In Sevres, France

• Only 1/7 SI units using physical artifact

• Δm/m = 30 ppb

Ideas for New StandardIdeas for New Standard

• X-Rays in Si– Avogadro’s #, NA

• 340 ppb (2003)

• Watt-balance: EM vs. G– Planck Constant, h

• 52 ppb (2005)

Link to "invariant" quantum phenomena

?

The Watt BalanceThe Watt Balance

• Balance Gravity Force with EMF• Find value for h, Planck’s Constant

me 2R h

c2

PhysicsPhysicsFaraday'sLaw

1c

E l B a

F I

z vz

z

Animation (if it works)Animation (if it works)

Measurements: VoltageMeasurements: Voltage

RDVM

Iind.

Hg Battery Stabilized I-Source

Zener Diode

Josephson Array Voltage

n f h

2eDetermine f with GPS Atomic clock

Measurements: VelocityMeasurements: Velocity

• 3 HeNe Laser systems give v and z

• Easily referenced to Meter standard:

• λHeNe = 632.99139822 nm

Measurement: CurrentMeasurement: Current

• Use DVM (Josephson ref.) to measure V across R

• Get R via Quantum Hall Effect

Iind.

DVMRH

hj e2

Measurement: GravityMeasurement: Gravity

• Easy to reference gravity!

• Use nearby gravimeter • < 10 meters away

• Reference with HeNe, GPS

• When scale is balanced

m1

gJvHeNe

VJRH

FI

v

Watt-Balance UCWatt-Balance UC

Basic references (error mode) nW/W

Mass (force) 15

Voltage, square error (current, voltage) 2

Resistance (current) 10

Time, linear error (voltage, current, velocity) 0.5

Length (velocity) 3

Local gravity acceleration (force) 30

TOTAL RMS 52