Power measurement in AC circuits can be quite a bit more complex than with DC circuits for the simple reason that phase shift complicates the matter beyond multiplying voltage by current figures obtained with meters. What is needed is an instrument able to determine the product (multiplication) of instantaneous voltage and current. Fortunately, the common electrodynamometer movement with …
An Overview Of Clamp Meter
Clamp-on ammeter or simply ‘clamp meter’ is an instrument that is used to measure the current flowing through a conductor. An AC Clamp meter basically consists of a current transformer in its jaws, bar CT usually. Utilizing the principle of current transformer, the reading will be displayed. Whereas a DC clamp meter is quite different. …
Measurement of insulation resistance (IR) – Part 1
Introduction The measurement of insulation resistance is a common routine test performed on all types of electrical wires and cables. As a production test, this test is often used as a customer acceptance test, with minimum insulation resistance per unit length often specified by the customer. The results obtained from IR Test are not intended …
Analog Data Acquisition with Transducers
Transducers measure power system parameters by sampling instrument transformer secondaries. They provide a scaled, low-energy signal that represents a power system quantity that the SA interface controller can easily accept. Transducers also isolate and buffer the SA interface controller from the power system and substation environments. Transducer outputs are dc voltages or currents in the …
Megger Insulation Resistance Test
As you know good insulation has high resistance; poor insulation, relatively low resistance. The actual resistance values can be higher or lower, depending upon such factors as the temperature or moisture content of the insulation (resistance decreases in temperature or moisture). With a little record-keeping and common sense, however, you can get a good picture …
Voltage Instrument Transformer (VT) – Introduction
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 …
