When the e.m.f. being measured is equal to the potentiometer voltage, the amplifier output Since polar potentiometer was developed by Dr. C.V. Drysdale , it is. Dr. C.V. Drysdales Alternating and Continuous Current Potentiometer The instrument comprises the standard Tinsley DC potentiometer of the time, with a phase. In a.c. potentiometers, another requirement is the control of stray e.m.f.s in fields Being a polar type, Drysdale – Tinsley a.c. potentiometer measures unknown.

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One is directly connected to power supply and the other one is connected in series with variable resistance and capacitor.

AC 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 potentiometet it does not affect the phase angle and it can be read on the scale fixed on the top of the instrument. The potentiometer – is then thrown on to the A.

This ammeter must read correctly with alternating and potentiomdter currents. Drysdale for the measurement of alternating potentials. The phase-shifting transformer is usually supplied by single-phase current. 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 the phase angle on a suitably divided scale.

But there is one major difference between their measurements, DC potentiometer only measures the magnitude of the unknown voltage.

Drysdale’s Alternating and Continuous Current Potentiometer – Computing History

These are potentiometed until the A. 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. The known source may be DC or AC.

Further, the phase relation between the circuit to be measured and that supplying the potentiometer may potengiometer any value from to Arrangements are provided for reversing the ammeter in order to eliminate the effect of stray fields.

The indicator for low frequencies is a vibration galvanometer which must be closely tuned to resonate to the frequency of the circuit.


The working phenomenon of DC potentiometer and AC potentiometer is same. We are extremely grateful for the very kind donation from Rosemary Helme of this Drysdale Alternating and Continuous Current Potentiometer. Where as, AC potentiometer measures both the magnitude and phase of unknown voltage by comparing it with known reference.

The rotor has a winding on it which supplies the potentiometer current. 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. The main potentiometer current must be kept at some known constant value. 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.

Coordinate type Potentiometer In coordinate AC potentiometertwo separate potentiometers are caged in one circuit as shown in the figure.

This is accomplished by supplying it through a phase-shifting transformer which consists of a stator wound with a circuit, which produces a rotating field in a closely-fitting rotor. There are two types of AC potentiometers: Thus, the resultant voltage of the coordinate AC potentiometer is And the phase angle is given by. Join our Mailing List by adding your email address below and be kept up to date with lots of information including: To obtain the necessary field distribution a split-phase scheme is used, part of the excitation being provided by a circuit containing a condenser and a resistance in series.

It has electrodynamometer type ammeter along with DC potentiometer and phase-shifting transformer which is operated by single phase supply. In a phase-shifting transformer, there is a combination of two ring-shaped laminated steel stators connected perpendicularly to each other as shown in the figure. 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.

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. There is a provision on the scale that it could read phase angle up to As it is necessary to have the splitphase circuit somewhere near the resonating point, it must be adjusted for changes of frequency. Connects Facebook Youtube Videos. Join our Mailing List by adding your email address below and be kept up to date with lots of information including:.


Calibration of watt meter. 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.

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Further references can be found at: These children deserve a space which is engaging and instructive, where they can feel a sense of adventure, exploration and surprise! 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.

Now to measure unknown e. Click on the Images For Detail. Applications of AC Potentiometer Measurement of self-inductance. The main circuit of the potentiometer must be supplied with alternating current drysdals 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.

Between the stators, there is laminated rotor having slots and winding which supplies voltage to the slide-wire circuit of the Potentiometer.

Drysdale ac polar potentiometer

The drsydale 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. For higher frequencies a telephone may be used. Web Design by Pure Energy.

By doing some adjustments in sliding contacts and rheostat, the whole circuit gets balanced and galvanometer reads zero at the balanced condition.

Now the in-phase component V A of the unknown e. Measures voltage as magnitude and phase from reference voltage.