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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The instrument comprises the standard Tinsley DC potentiometer of the time, with a phase shifter, Weston dynamometer voltmeter, selection and potentiomteer switches and terminal panels for connection of galvanometers, DC and AC measuring and supply voltages.

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 and Continuous Current Potentiometer – Computing History

Where as, AC potentiometer measures both the magnitude and phase of unknown voltage by comparing it with known reference. 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.

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

In order to obtain a balance, as indicated by the potentiomeher instrument, it must be possible to give to the potentiometer current any phase displacement relative to that of the potential supplying it. This ammeter must read correctly with alternating and continuous currents. For higher frequencies a telephone may be potetniometer. By doing some adjustments in sliding contacts and rheostat, the whole circuit gets balanced and galvanometer reads zero at the balanced condition. Further references can be found at: Between the stators, there is laminated rotor having slots and winding which supplies voltage to the slide-wire circuit of the Potentiometer.

There are two types of AC potentiometers: Related pages What is Potentiometer?


It also supplies 6 volts to potentiometers. This is accomplished by supplying it through a phase-shifting transformer which consists of a pktentiometer wound with a circuit, which produces a rotating field in a closely-fitting rotor. The indicator for low frequencies is a polae galvanometer which must be closely tuned to resonate to the frequency of the circuit. Join our Mailing List by adding your email address below and be kept up to date with lots of information including:.

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. Now to measure unknown e. Arrangements are provided for reversing the ammeter in order to eliminate the effect of stray fields.

There is a provision on the scale that it could read phase angle up to The main potentiometer current must be kept at some known constant value. The first one is named as the in-phase potentiometer which is used to measure the in-phase factor of an unknown e. Click on the Images For Detail. The rotor has a winding on it which supplies the potentiometer current. There are two step-down transformers T 1 and Potentiometerr 2 which isolate potentiometer from the line and give an earthed screens protection between the winding.

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

Please be assured that any amount you feel able to donate will make an immediate and significant impact. To obtain the necessary field potentiometeg a split-phase scheme is used, part of the excitation being provided by a circuit containing a condenser and a resistance in series.

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.

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. Further, the phase relation between the circuit to be measured and that supplying the potentiometer may have any value from to 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.


Web Design by Pure Energy. The function of the series components is to maintain constant AC supply in the potentiometer by doing small adjustments in it. 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.

Since opening at the end ofover 5, children have visited the Centre. But there is one major difference between their measurements, DC potentiometer only measures the magnitude of the unknown voltage. Coordinate type Potentiometer In coordinate AC potentiometertwo separate potentiometers are caged in one circuit as shown in the figure.

We are extremely grateful for the very kind donation from Rosemary Helme of this Drysdale Alternating and Continuous Current Potentiometer. Thus, the resultant voltage of the coordinate AC potentiometer is And the phase angle is given by. 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.

Drysdale for the measurement of alternating potentials. Applications of AC Potentiometer Measurement of self-inductance.

These are adjusted until the A. Calibration of watt meter.

AC Potentiometer

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.

When current start flowing from stators, the rotating field is developed around the rotor and due to it e.

As it is necessary to have the splitphase circuit somewhere near the resonating point, it must be adjusted for changes of frequency.