**WELLOG ****UNITS OF MEASUREMENT**

©
2016 WELLOG

Revised
11-07-2016

Confused
about units of measurement?

Newtons?
Pascals? Teslas?

When
performing calculations, it is important to decide which system of measurement
to use.

Three
systems are in use in the world today.

- Centimeters,
Grams, and Seconds (CGS)

- Meters,
Kilograms, and Seconds. (MKS)

- System
International (SI)

Centimeters,
Grams, and Seconds (CGS):

This
system was introduced in 1874 by the British Association for the advancement of
Science. It was and has been used in scientific and engineering applications
involving small quantities.

Meters,
Kilograms, and Seconds (MKS):

This
system was proposed in 1889 by the International Bureau of Weights and Measures
(BIPM). Depending on the scale of measurement, scientists and engineers use CGS
to measure small quantities and MKS when measuring large quantities.

What
happened?

The
Tenth General Conference on Weights and Measures (CGPM) adopted MKS as the
standard for basic units for all international weights and measures in 1954.

The
Eleventh General Conference on Weights and Measures adopted the International
System of Units (SI) for this collection of units in 1960.

Today
(after year 2000) the only system acceptable for use in testing and measurement
is the SI system. Ref: NIST.

Visit
http://www.physics.nist.gov , http://www.physics.nist.gov/cuu/units , http://www.physics.nist.gov/Pubs/SP811/sec05.html

System
International (SI):

The
basic units are…

Mass
measured in Kilograms. kg

Length
measured in Meters. m

Time
measured in Seconds. s

Amount
of substance measured in Moles. mol

Electric
current measured in Amperes. A

Thermodynamic
temperature measured in Kelvin. K (not “degrees
Kelvin”) Ref CGPM, 1967

Luminous
intensity measured in Candela. cd

SI
DERIVED UNITS:

Force
is measured in Newtons. N = kg*m/s^{2}

Pressure/stress
is measured in Pascals. Pa = N/m^{2}

Energy
or work in Joules. J
= N * m

Power
is measured in watts. W = J/s

Potential/EMF
is measured in volts. V
= W/A

Magnetic
flux is measured in webers. Wb = V*s

Magnetic
flux density is measured in teslas. T = Wb/m^{2}

Inductance
is measured in henrys. H = Wb/A

Temperature, measured in Celsius C = K – 273.15

Electric
charge is measured in Coulombs. C = A*S

Resistance
is measured in ohms. W
= V/A

Conductance
is measured in siemens. S = 1/W

Capacitance
is measured in farads. F = C/V

Frequency
is measured in Hertz. Hz = 1/s

Illuminance
is measured in lux. lx
= lm/m^{2}

Luminous
flux is measured in lumens. Lm = cd*sr

Note:
this list is not all inclusive – refer to http://www.physics.nist.gov/
for more units.

WELLOG
endorses measurement in SI units. Some text material on this website may
reference units not approved or accepted by NIST SI. Such references are used in text material for
clarity and to avoid conflict with earlier established text materials.
Conversions are available for conversion of scientific units from unaccepted
units to modern accepted SI units.

If
you have questions, WELLOG has answers! Contact info@wellog.com for answers to your questions!