A.C. POTENTIOMETER. Its principle is same as a But in an a.c. potentiometer, not only the magnitudes but phases as well DRYSDALE POLAR TYPE AC. Posts about polar type ac potentiometer written by Pragnarongali. The working principle of the AC potentiometer is same as that of the DC potentiometer, i.e., the unknown voltage is determined by Polar Type Potentiometer.

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The combination of dial resistors and slide wire is set to the value of the standard cell voltage.

The instrument is balanced by the main dial and the slide wire, leaving the protective resistance again in the circuit. The single range potentiometer can be modified to include a second measuring range of lower value by adding two range resistors and a range drusdale. Thus, the voltage and current may vary at different power factor. Further, the phase relation between the circuit to be measured and that supplying the potentiometer may have any value from to Circuit Globe All about Electrical and Electronics.

As the vibration galvanometer has also to be adjusted for such changes, it is necessary to have a source of a very steady frequency and voltage for satisfactory working. As it is necessary to have the splitphase circuit somewhere near the resonating point, it must a.c.potentjometer adjusted for changes of frequency. The reading of a sensitive dynamometer type ammeter in the main circuit is noted.

Measures voltage as magnitude and drysdsle from reference voltage. The working current is checked by returning to the calibrate position. The following are the important factor which must be considered for their operation. Join our Mailing List by adding your email address below and be kept up to date with lots of information including: In these instruments, the magnitude of the unknown voltage is read from one scale and its phase angle, with respect to some reference phasor, is read directly from a second scale.


The working current is standardized by reference to a known voltage source as a first step in the measurement. The following are the steps to be followed during a potentiometric measurement: Now to measure unknown e. By continuing to use this website, you agree to their use. The main potentiometer current must be kept at some known constant value.

Ammeter Calibration — The measurement of the alternating current may be measured by the use of non-inductive standard resistor with the potentiometer. The rotor has a winding on it which supplies the potentiometer current. Arrangements are provided for reversing the ammeter in order to eliminate the effect of stray fields. The operation of the AC potentiometer is quite drysxale as compared to the DC potentiometer.

In order to operate the galvanometer at its maximum sensitivity, provision is made to short the protective resistance when near the balance conditions.

Drysdale ac polar potentiometer

Further references can be found at: It has electrodynamometer type ammeter along with DC potentiometer pilar phase-shifting transformer which is operated by single phase supply. Polar type Potentiometer In such type of instruments, two separate scales are used to measure magnitude and phase angle on some reference of the unknown e.


This is accomplished by supplying it through a phase-shifting a.c.otentiometer which consists of a stator wound with a circuit, which produces a rotating field in a closely-fitting rotor. This principle of operation of all potentiometers is based on the following basic circuits.

Other Applications — The AC potentiometer is used for engineering measurement in which the accuracy of 0. Measurements of Self Reactant of a Coil — The standard reactance is placed in series with the coil whose reactance is to be measured.

Drysdale’s Alternating and Continuous Current Potentiometer – Computing History

The working phenomenon of DC potentiometer and AC potentiometer is same. This is done by switching it over on to a continuous current circuit, which is adjusted until a balance is obtained at the proper setting, when a Weston cell is connected up in the usual manner. The protective resistance is left in the circuit to avoid damage to the galvanometer during the initial stages of adjustment.

Leave a Reply Cancel reply Your email address will not be published. The AC potentiometers are classified by the value measured by the potentiometer dial and scales.

The phase displacement of the rotor emf is equal to rotor movement angle from its original position and it is related to the stator supply voltage.

The known source may be DC or AC. The higher voltage is measured by either using the volt box ratio or two capacitors in series with the potentiometer.