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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For higher frequencies a telephone may be used. The higher voltage is measured by either using the volt box ratio or two capacitors in series with the potentiometer. Measurements of Self Reactant of a Coil — The standard reactance is placed in series with the coil whose reactance is to be measured. 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. But there is one major difference between their measurements, DC potentiometer only measures the magnitude of the unknown voltage.

This ammeter must read correctly with alternating and continuous currents. Circuit Globe All about Electrical and Electronics. The AC potentiometer may be broadly classified as. The reading of a sensitive dynamometer type ammeter in the main circuit is noted.

Your email address will not be published. We are pootentiometer grateful for the very kind potentiomeeter 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 potentiometee known reference. In order to obtain a balance, as indicated by the detecting instrument, it must be possible to give to the potentiimeter current any phase displacement relative to that of the potential supplying it.

The indicator for low frequencies is a vibration 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: There is a provision on the scale that it could read phase angle up to Arrangements are provided for reversing the ammeter in order to eliminate the effect of stray fields. The following potentiometre the important factor which must be considered for their operation.


The phase shifting transformer is connected to the potentiometer to vary the phase of the voltage on the current. 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.

Related pages What is Potentiometer? The AC potentiometers are classified by the value measured by the potentiometer dial and scales. Click on the Images For Detail.

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

Measures voltage as magnitude and phase from reference voltage. The working principle of the AC potentiometer is same as that of the DC potentiometer, i. 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 potentilmeter of galvanometers, DC and AC measuring and supply voltages.

Further, the phase relation between the circuit to be measured and that supplying potsntiometer potentiometer may have any value from to The operation of the AC potentiometer is quite complicated as compared to the DC potentiometer. Applications of AC Potentiometer Measurement of self-inductance. When current start flowing from stators, the rotating field is developed around the rotor and due to it e. Hence the value of the unknown emf is known. 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.

Drysdale for the measurement of alternating potentials. And when both of them are equal the galvanometer indicates the null point. As it is necessary to have the splitphase circuit somewhere near the resonating point, it must be adjusted for changes of frequency.

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.


Ammeter Calibration — The measurement of the alternating current may be measured by potebtiometer use of non-inductive standard resistor with the potentiometer.

Drysdale’s Alternating and Continuous Current Potentiometer – Computing History

The AC potentiometer is also used for measuring the voltage which must be resolved into two components. Drysdale’s Alternating and Continuous Current Potentiometer.

The potentiometer – is then thrown on to the A.

There are two types of AC potentiometers: The main potentiometer current must be kept at some known constant value. It has electrodynamometer type ammeter along with DC potentiometer and phase-shifting transformer which is operated by single phase supply.

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

The known source may be DC or AC.

AC Potentiometers

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.

It gives the accurate results in magnetic testing and precise testing of instrument drjsdale. The first one is named as the in-phase potentiometer which is used to measure the in-phase factor of an unknown e.

Please be assured that any amount you feel able to donate will make an immediate and significant impact. Drysdale’s Alternating and Continuous Current Potentiometer The drysdqle 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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