Instrument transformers are primarily used to provide isolation between the main primary circuit and the secondary control and measuring devices. This isolation is achieved by magnetically coupling the two circuits. In addition to isolation, levels in magnitude are reduced to safer levels. Instrument transformers are divided in to two categories: voltage transformers (VT) and current …
Moving Iron Instruments – Voltmeter and Ammeter
Construction and basic principle operation of moving-iron instruments Moving-iron instruments are generally used to measure alternating voltages and currents. In moving-iron instruments the movable system consists of one or more pieces of specially-shaped soft iron, which are so pivoted as to be acted upon by the magnetic field produced by the current in coil. There …
D’Arsonval Meter Movement
The most commonly used sensing mechanism used in DC ammeters, voltmeters, and ohm meters is a current-sensing device called a D’Arsonval meter movement (Figure 1). The D’Arsonval movement is a DC moving coil-type movement in which an electromagnetic core is suspended between the poles of a permanent magnet. The current measured is directed through the …
How To Use A Digital Multimeter
A digital multimeter is used to make various electrical measurements, such as AC and DC voltage, AC and DC current, and resistance. It is called a multimeter because it combines the functions of a voltmeter, ammeter, and ohmmeter. Multimeters may also have other functions, such as diode and continuity tests.
Ethernet History
Ethernet is the most popular and widely deployed network technology in the world. In 1973, while working on a way to link the Xerox “Alto” computer to a printer, Bob Metcalfe designed and tested the first Ethernet network. This first Ethernet network defined the physical cabling required of a connected device and defined the standard …
Economic advantages of power factor correction
Power supply authorities apply a tariff system which imposes penalties on the drawing of energy with a monthly average power factor lower than 0.9. The contracts applied are different from country to country and can vary also according to the typology of costumer: as a consequence, the following remarks are to be considered as a …
Megger Tests
The insulation resistance meter test method for determining the condition of electrical insulation has been widely used for many years as a general nondestructive test method. A serious limitation of this test is that its operating voltage of 500 to 1,000 volts will not always detect insulation punctures, whereas the higher voltages used by the …
