Techniques Realisation (metrology)

1 techniques

1.1 time

1.1.1 direct measurement of solar time
1.1.2 timekeepers
1.1.3 time generators


1.2 length
1.3 volume
1.4 mass
1.5 electric charge
1.6 temperature
1.7 photometry
1.8 amount of substance

techniques
time

the realisation of time has gone through 3 phases. during both first , second phases, man used solar time—during first phase, realisation of time observing earth s rotation using such devices sundial or astrolabe. during second phase actual timing devices such hourglasses or clocks used. if user needed know time-of-day rather elapsed time, clocks synchronized astronomical time. third phase made use of clocks sufficiently accurate measure variations in earth s rotation—such clocks taking on rotation of earth prime measure of time.

direct measurement of solar time

sundials , astrolabes

timekeepers

accuracy of clocks

time generators

radiation frequency & si

length

units of length, along mass (or weight) , time, 1 of earliest quantities measured man. historically 2 distinct approaches used - 1 use naturally occurring phenomenon such particular seed or part of human body, other use standard length held community leader.

natural units - barleycorn, feet
regal units - measures held ruler
using speed of light

an example of modern realisation realisation of meter in terms of optical frequency standards.

volume

jugs etc. in ancient times
not base unit in si

mass

grains
artefacts held governments
watt balance & avogadro experiment

electric charge

silver nitrate deposits
force between conductors
charge on electron

temperature

freezing & boiling water
non-linearity etc.
boltzmann s constant

photometry

sensitivity of eye

amount of substance

development of mole




^ quinn, t. j. (2003). practical realisation of definition of metre, including recommended radiations of other optical frequency standards (2001) (pdf). metrologia. 40: 103–133. doi:10.1088/0026-1394/40/2/316. retrieved 6 december 2013.