Category Archives: Electrical measuring instrument

Dynamometer type single-phase power factor meter

Construction: It consists of a fixed coil FF (split into two parts) which carries the current of the circuit under test. So, the magnetic field produced by this coil is proportional to the main current. The identical pressure coils A and B pivoted on a spindle constitutes the moving system. Pressure coil A has a non-inductive resistance R… Read More »

CRT (Cathode ray tube)

The main part of oscilloscope is CRT. It is an electronic device that produce visual re presentation of electric effect. A cathode ray tube mainly consists of the following: Electron gun Electrostatic deflection Envelop0e and screen The main component of oscilloscope cathode ray tube (CRT). This is also used in television, radar, and computer displays. The tube is… Read More »

Polar type AC potentiometer

Construction and Working Principle:  This instrument consists of an ordinary dc potentiometer in which the resistance coils are non- inductive and the auxiliary apparatus like Drysdale phase shifting transformer and transfer instrument. Drysdale Phase Shifting Transformer – The phase shifting transformer consists of a laminated silicon steel stator which houses a two or three phase winding. The rotor… Read More »

Gall-tinsley (co-ordinate type) a.c. Potentiometer

Connection of Gall – Tinsley a.c. Potentiometer This potentiometer consists of two separates potentiometer circuits enclosed in a common case. One is called the “in-phase” potentiometer and the other the “quadrature” potentiometer. The slide-wire circuits are supplied with currents which have a phase difference of 90˚. On the first of these potentiometers, that component of the ‘unknown’ voltage… Read More »

Construction and principle of operation of current transformer

Current transformer (C.T.): The current transformers are of family two types. They are Wound type Bar type Wound type C.T. A current transformer in which the primary winding consists of more than one full turn wounded on core is called wound type. The simplest form of current transformer is the ring type or window type which is shown… Read More »

Measurement of earth resistance by fall of potential method

On these factors the resistance of earthing system are depends- Shape and material of electrode or electrodes used. Depth in the soil at which the electrodes are buried. Specific resistance of soil surrounding and in the neighborhood of electrodes. The specific resistance of the soil varies from one type of soil to another type of soil. Means its… Read More »