Measuring tool is a tool that can be used to determine the results of the comparison between a quantity you want to know the standards used. An important function of the measuring instrument in particular measuring devices of electrical quantities is to know the value that has been determined as eligible limitation or failure of equipment or electricity network will be operated. In our measurements a quantity mem-compare with the amount of the standard. So that the measurements need to know the amount, units and dimensions.

Magnitude is something that can be measured. The amount consists of: (1) The amount of the base; ie, the amount of which does not depend on the size of the other, and (2) The amount of the derivative; is the amount derived from the basic magnitudes, and a combination of the magnitude of the base. Power generation, power grids, power distribution and utilization of electric power unit relating denganbesaran and determine its size.

Therefore, before we deepen all the problems in the electricity business, you should explore in advance of the standard units used universally applicable in order to apply them correctly. For science and technology, the units can be regarded as currency. With currency transactions you can do anything, anytime, and anywhere.

Likewise with the unit. There are two systems of units that can be used, namely (1) the International System, commonly known as SI units, and (2) System Imperial (English), which is a unit system that applies in Europe. SI unit system most widely used around the world, and this book, apply both the unit system. 1960 on international agreements designated as the international system (SI).

SI system used six basic unit, namely meter, kilogram, second, and ampere (MKSA) and as an additional base unit is degrees Kelvin and a candle (candela) is a unit of temperature and light intensity, as shown in Table 10.1.

Other units that can express the fundamental units called derivative units. To ease some of the derivatives unit has been given a new name, for example in the SI called watt power which replaces the j / s. Table 10.2 shows that beralku derived unit in the techniques of electricity.

British Science Association development has been set as the basic unit to centimeters long and gram as the basic unit for the masses. From here developed system-gramsekon centimeters (CGS). In the CGS electrostatic system, derived from the unit of electrical charge centimeter, gram, and second by establishing that permissivitas vacuum on Coulomb’s law regarding electrical charge is one.

Derivative units to the electric current and the electric potential in the electromagnetic system, the ampere and volts used in practical pengukuranpengukuran. Both of these units along with one of the other units such as: coulomb, ohm, henry, farad, and so forth are combined in a third unit called practical system (practical system).

**Factors Multiples Decimal**

The value of the amount which we will measure has a very large range, from very small to order very large. To facilitate the reading of measuring value commonly used decimal multiplication factor. Table 10.3 shows the decimal multiplication factor intended.

Table 10.3 Factors Multiples Decimal