The Potentiometer is an instrument which measures unknown voltage by balancing it with a known voltage. The known source may be DC or. Definition of DRYSDALE POTENTIOMETER: An ac potentiometer of the polar type, comprising a phase-shifting transformer and resistive voltage divider. Definition: The potentiometer which is used for measuring the phase and the magnitude of the unknown emf by comparing it with the known emf such type of.

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Ammeter Calibration — The measurement of the alternating current may be measured by the use of non-inductive standard resistor with the potentiometer. The AC potentiometer may be broadly classified as. When current start flowing from stators, the rotating field is developed around the rotor and due to it e. And when both of them are equal the galvanometer indicates the null point.

There are two step-down transformers T 1 and T 2 which isolate potentiometer from the line and give an earthed screens protection between the winding. 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.

Related pages What is Potentiometer? Applications of AC Potentiometer Measurement of self-inductance.

AC Potentiometer

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 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 phase shifting transformer is connected to potentiometdr potentiometer to vary the phase of the voltage on the potentiometet. 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.

But there is one major drysdalw between their measurements, DC potentiometer only measures the magnitude of the unknown voltage. There are two types of AC potentiometers: It has electrodynamometer type ammeter along with DC potentiometer and phase-shifting transformer which is operated by single phase supply.


These are adjusted until the A. As it is necessary to have the splitphase circuit somewhere near the resonating point, it must be adjusted potetniometer changes of frequency. The main potentiometer current must be kept at some known constant value. The instrument comprises the standard Tinsley DC potentiometer of the time, with a phase shifter, Weston dynamometer voltmeter, selection potentjometer change-over switches and terminal panels for connection of galvanometers, DC and AC measuring and supply voltages.

It also supplies 6 volts to potentiometers. Now the in-phase component V A of the unknown e. The potentiometer, which is the universal instrument by which currents are determined in terms of a difference of potential between the end of a known resistance, has been developed by C.

Thus, the voltage and current may vary at different power factor. Drysdale for the measurement of alternating potentials. The “balance” is obtained by successive approximation of the usual adjustment of the potentiometer contacts dial and slide wire reading and of the phase-shifting transformer until the indicator shows no deflection. Since opening at the end ofover 5, children have visited the Centre.

The rotor has a winding on it which supplies the potentiometer current. Please be assured that any amount you feel able to donate will make an immediate and significant impact. The coordinate type potentiometer has two scales to read the inphase V 1 component, and the quadrature component V 2 of the unknown voltage V. S 1 and S 2 are signs changing switches which are used to change the polarity of the test voltage if it is required for balancing the Potentiometer.

Hence the value of the unknown emf is known. The following are the important factor which must be considered for their operation. Now to potentiometre unknown e.

AC Potentiometers

Voltmeter Calibration — The AC potentiometer directly measures the low voltages up to 1. Web Design by Pure Energy. We are extremely grateful for the very ootentiometer donation from Rosemary Helme of this Drysdale Alternating and Continuous Current Potentiometer.


The working phenomenon of DC potentiometer and AC potentiometer is same. The known source may be DC or AC. The AC potentiometer is also used for measuring the voltage which must be resolved into two components. Your email address will not be published. The reading of a sensitive dynamometer type ammeter in the main circuit is noted.

Join our Mailing List by adding your email address below and be kept up to date with lots of information including:. The potentiometer – is then thrown on to the A.

The first one is named as the in-phase potentiometer which is used to measure the in-phase factor of an unknown e. Arrangements are provided for reversing the ammeter in order to eliminate vrysdale effect of stray fields.

Where as, AC potentiometer measures both the magnitude and phase of unknown voltage by comparing it with known reference. Drysdale’s Alternating and Continuous Current Potentiometer.

The function of the series components is to maintain constant AC supply in the potentiometer by doing small adjustments in it. For higher frequencies a telephone may be used. Further references can be found at: Leave a Reply Cancel reply Your email address will not be published. Measurements of Self Reactant of a Coil — The standard reactance is placed in series with the coil whose reactance is to be measured.

The higher voltage is measured by either using the volt box ratio or two capacitors in series with the potentiometer. The whole arrangement of the winding is done in such a way that the magnitude of the induced emf in the rotor may change but it does not affect the phase angle and it can be read on the scale fixed on the top of the instrument. 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.