﻿VK5AJL - Metric System THE MKS METRIC SYSTEM
THE STANDARD METRIC SYSTEM WITH ELECTRONIC SHORTCUTS

MULTIPLIERS

This page details the MKS system and not the SI system. Essentially they are the same. The rules quoted here apply only to MKS. MKS stands for Metre/Kilogram/Second while SI for the French "Système international" or International System. There is no difference in the basic definitions except there is no "centimetre", "decimetre" etc. in MKS. The SI system has these extra units to facilitate references to units of similar size in more ancient systems like Imperial Measure. MKS is for the purists.

The metric system involves units of the entity being measured and a multiplier. The multiplier is always a multiple of 1000. Once the measurement exceeds a thousand or 1/1000, the next multiplier should be used. 1000Gl (1000 Gigalitres) should be expressed as 1Tl (1 Teralitre). The multipliers greater than one all use a capital letter except for "kilo" and those less, a lower case letter.

Calculating things concerned with radio is so easy, I can't understand why people would want to be converting between 2 feet 5.2 inches and 2.43 feet.

 Multiplier Prefix Abbreviation 1024=1,000,000,000,000,000,000,000,000 yotta Y 1021=1,000,000,000,000,000,000,000 zetta Z 1018=1,000,000,000,000,000,000 exa E 1015=1,000,000,000,000,000 peta P 1012=1,000,000,000,000 tera T 109=1,000,000,000 giga G 106=1,000,000 mega M 103=1,000 kilo k 100=1 - none - unit 10-3=1/1,000 milli m 10-6=1/1,000,000 micro μ 10-9=1/1,000,000,000 nano n 10-12=1/1,000,000,000,000 pico p 10-15=1/1,000,000,000,000,000 femto f 10-18=1/1,000,000,000,000,000,000 atto a 10-21=1/1,000,000,000,000,000,000,000 zepto z 10-24=1/1,000,000,000,000,000,000,000,000 yocto y

NOTE ON BASIC AND DERIVED UNITS

Basic and derived units are defind for the MKS system but the reasoning for this can be argued. Some say the "candela" (the unit for light intensity) is a basic unit but it is equivalent to an amount of energy so I have listed it as derived. I personally would have had energy as a basic unit and mass as a derived unit 1kg = 89.875517873681764PJ (PetaJoules) but that's just me.

BASIC UNITS

Length - metre (The M in MKS)

One metre is defined as the distance travelled by light in a vacuum in 1 / 299,792,458 second.

Mass - kilogram, kg (The K in MKS)

The standard for mass is the kilogram and is the mass of a platinum-iridium alloy bar kept in the International Bureau of Weights and Measures, located in Sèvres in France. It is strange this definition is of 1000 of something. It would seem more logical to have called the mass of the reference artifact a gram since it is only a matter of definition.

Time - second (The S of MKS)

The second is defined as the duration of 9,192,631,770 cycles of the radiation associated with a specified change in energy level, of the cesium-133 atom.

DERIVED UNITS

Force - newton

The force required to accelerate one kilogram at a rate of 1 metre per second per second.

Energy - joule

The work done by displacing a force of one newton through a distance of one metre. This is a particularly bad definition because it defines energy in terms of work only but it is impossible to do any work without producing heat which is also energy and also measured in joules.

Electric current - ampere

The ampere is defined as the current that, when flowing through each of two long parallel wires separated by one metre in free space, results in a force between the two wires of 2 x 10-7 newton for each metre. This works out at 1 coulomb of charge every second.

Power - watt

Rate of energy flow (released, dissapated, consumed etc.) of one joule per second.

Electric resistance - ohm

The resistance whereby a current of one amp dissapates one watt or one joule of energy per second.

Electromotive force - volt

The electrical force or potential necessary to produce a current of one ampere through a resistance of one ohm.

Electric charge - coulomb

The negative charge represented by 6.24150962915265 x 1018 electrons. This is the number of actual electrons flowing past a point in one second when a current of one amp flows.

The capacitance which will charge to one volt using a current of 1 amp in one second. This is also the capacitance that will store 1 joule of energy at potential of 1 volt.

Inductance - henry

One henry is the inductance that, if it has rate of change of 1 amp per second, will have a resulting potential of 1 volt. If 1 amp is flowing through a circuit with a potential of 1 volt and the energy stored in the circuit is 1 joule then the inductance of the circuit is 1 henry.

Temperature - degrees Celsius (sometimes called centigrade) or degrees kelvin

The centigrade temperature scale is based on the triple point of water, that is, at a specific pressure and temperature, water, ice and steam are in equilibrium. The temperature of the triple point is 273.16o kelvin (pressure is 611.2Pa) and is .01o on the centigrade scale. This means that at standard atmospheric pressure, pure water melts at very close to 0oC and boils at very close to 100oC. Since a change in temperature is the same on both kelvin and celcius scales, it makes little difference which is used as the definition.

Light intensity - candela

The luminous intensity of 1.666... x 10-6 square metres of a radiating cavity at the temperature of freezing platinum or 2,042oK.

In addition to the prefixes and units, values are often given by using the abbreviation of the unit as a decimal point eg. 4p7 for 4.7 picofarad, 13v8 for 13.8 volts, 5k6 for 5.6 kilohms. This may appear, at first to be a little confusing but resistance values are usually greater than 1 ohm while capacitors are generally smaller than a microfarad. This leaves little room for overlap. Sometimes resistance values may be in tenths of ohms and, in this case a value such as 0R1 is used for 0.1 ohms or 100 mΩ (100 milliohms)

Ponuds, feat, inchs, farenheight (see, I can't even spell them) etc.

Sorry, No idea what they are or how they might be used or what brain dead moron would want to. All text and images on this site are Copyright to John Langsford (vk5ajl).
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I think that's pretty fair, don't you?