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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Applications of AC Potentiometer Measurement of self-inductance. It also supplies 6 volts to potentiometers. The switch is thrown to the calibrate position and the galvanometer key is a.c.potentioeter while the rheostat is adjusted for zero deflection on the galvanometer.

The main circuit of the potentiometer must be supplied with alternating current of exactly the same frequency as that in the circuit to be measured, which means in practice that they must be supplied from the same source. Drysdale’s Alternating q.c.potentiometer Continuous Current Potentiometer.

The reading of a sensitive dynamometer type ammeter in the main circuit is noted.

Drysdale’s Alternating and Continuous Current Potentiometer – Computing History

plar The most important difference between a d. The AC potentiometer is also used for measuring the voltage which must be resolved into two components. In order to obtain a balance, as indicated by the detecting instrument, it must be possible to give to the potentiometer current any phase displacement relative to that of the potential supplying it. There is one dial switch with 15 steps, each having poolar precision resistor. The operation of the AC potentiometer is quite complicated as compared to the DC potentiometer.


The rotor has a winding on it which supplies the potentiometer current. By continuing to use this website, you agree to their use. A rotation of the rotor of the phase-shifting transformer through o has the effect of producing a phase shift of the same value, and a pointer on the rotor axis indicates a.c.potentiometre phase angle on a suitably divided scale.

The protective resistance is left in the circuit to avoid damage to the galvanometer during the initial stages of adjustment.

It is an instrument designed to measure an unknown voltage by comparing it with a known voltage. Thus, the voltage and current may vary at different power factor.

Drysdale’s Alternating and Continuous Current Potentiometer The instrument comprises the standard Tinsley DC potentiometer of the time, with a phase shifter, Weston dynamometer voltmeter, selection and change-over switches and terminal panels for connection of galvanometers, DC and AC measuring and supply voltages.

Thus, the resultant voltage of the coordinate AC potentiometer is And the phase angle is given by. The working current is standardized by reference to a known voltage source as a first step in the measurement. Now the in-phase component V A of the unknown e. The following are the important factor which must be considered for their operation. The known voltage may be supplied by a standard cell or any other known voltage-reference source.

Connects Facebook Youtube Videos. As balance is approached, the protective resistance is shorted and final adjustments are made to obtain a true balance condition.


The combination of dial resistors and slide wire is set to the value of the standard cell voltage. Drysdale for the measurement of alternating potentials. A.c.potwntiometer AC potentiometers are classified by the value measured by the potentiometer dial and scales.

In order to operate the galvanometer at its maximum sensitivity, provision is made to short the a.c.potentiomefer resistance when near the balance conditions. As it is necessary a.c.poentiometer have the splitphase circuit somewhere near the resonating point, it must be adjusted for changes of frequency. A key and a protective resistance is used in the galvanometer resistance. We are extremely grateful for the very kind donation from Rosemary Helme of this Drysdale Alternating and Continuous Current Potentiometer.

The working current is checked by returning to the calibrate position. The following are the steps to be followed during a potentiometric measurement:. This site uses cookies. As zero deflection is approachedthe protective resistance is shorted drysadle final adjustments are made with the rheostat control. For higher frequencies a telephone may be used.

If the dial settings are exactly the same as in the a.c.potrntiometer calibration procedure, a valid measurement has been made. One is directly connected to power supply and the other one is connected in series with variable resistance and capacitor.