Crompton Potentiometer complete setup for physics experiment. The slide-wire type of potentiometer described in the previous article is not a practical form of construction. The long slide wire is awkward, and. Potentiometers. Introduction. A Basic dc Potentiometer. Crompton’s dc Potentiometers. Applications of dc Potentiometers. AC Potentiometers.

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DC Crompton’s Potentiometer or Laboratory Type Potentiometer

This is essential so that once the instrument has been calibrated on x 1 range, calibration of the x 0. The two ranges are obtained by using two resistors R 1 and R 2 and a range selecting switch S. The value of the unknown emf is obtained by adding potentometer galvanometer reading to the main dial setting.

There is also a single turn circular slide wire. This potentiometer uses the Kelvin Varley arrangement shown below.

The slide wire of the calibrating circuit is set to read the emf of the standard cell which is connected to the potentiometer. If this is not done the voltage drop in switch contact resistances and leads would render the converge of middle dial to less than 0.

This instrument has two ranges: In actual practice the resistance of the second dial is greater than that between two studs in the main first dial, so that potentiometed voltage drop across the second dial is greater than 0. Get best deals for coconut.

A centre zero type galvanometer is included in the circuit to indicate deflection. The switch S is then thrown to the operate position and unknown emf is read by adjusting the measuring circuit dial and slide wire. Chand ” is the best in industry. This fixes the working current to its proper value.

Measurements are subject to stray thermal and contact EMF s in the potentiometergalvanometer and the measuring circuits. This completes the standardisation process for the potentiometer.

After completion of standardisation, the switch ‘S’ is thrown to operate position thereby connecting the unknown emf into the potentiometer circuit. Amarnath Reddy I am a graduate in electrical engineering and blogger by passion. Duo range type potentiometer. The following steps are used when making measurements with the above potentiometer: The working current of the potentiometer is 10 mA and therefore each step of dial switch corresponds to cromptin.


This means that current through the galvanometer will always be proportional to the out of balance current whatever may be the setting of the main dials. The above requirement means that the voltage E ac in above figure remains the same for both positions of range switch S. If you have questions, then you can email me palakalaamarnath gmail. Provided in different specifications, this range is used for various medical and commercial applications. Direct reading potentiommeter, improved from with standardizing coil consisting of 8 coils and a circular slide wire The scale is divided into parts with potential drop of mill volts Fine and coarse rheostats are provided for adjusting the slide wire current Range 0.

The single-range potentiometer shown above is frequently constructed to cover a range of 1. Laboratory-type or DC Crompton’s Potentiometer: The standardising circuit may be checked for the constancy of working current, anytime during the measurements by simply throwing the switch S back to calibrate position.

The third dial is obtained from a shunt circuit which permits a true zero and a small negative setting to be obtained. Modern laboratory type potentiometers use calibrated dial resistors and a small circular wire of one or more turns, thereby reducing the size of the instrument. This process does not disturb the measuring circuit while convenience and speed of measurements are increased.

The moving arm of middle dial carries two arms spaced two studs apart. As the balance or null point is approached, the protective resistance is shorted so as to increase the sensitivity of the galvanometer. A drop potengiometer 1. These EMFs may be of the order of one to several microvolts and are difficult to locate and control. All modern potentiometers incorporate a separate standard cell dial circuit calibrating circuit. The figure below shows a deflectional potentiometer.

Thus the galvanometer scale can be calibrated to read the out of balance emf directly. This condition is satisfied only when the total battery current has the frompton value for each measuring range. If the cgompton reading does not agree with the old one, the second measurement of unknown emf must be made. There is one dial switch with fifteen steps, each having a precision resistor. The operation of the duo range potentiometer may be more easily understood and analysed by redrawing in its simplified form by omitting the galvanometer and calibration standardising circuit.


The standardisation of the potentiometer is checked again by returning the switch S to the calibrate position. The potentiometer is used to monitor the value of temperature where a thermocouple is employed. Number of Employees 11 to 25 People. In the above figure, the total resistance of measuring of the circuit, Rm consists of resistance of the main dial in series with that of slide wire.

Crompton Potentiometer Complete Setup

The dial settings are kept exactly the same as in the original standardisation process. The protective resistance is kept in the circuit in the initial stages so as to protect the galvanometer from being getting damaged. I agree to the terms and privacy policy. The vernier potentiometer reads to the increment of 0.

This provides a means of standard cell balance resistance to suit the emf value of the particular standard cell used. The galvanometer circuit includes a set of compensating resistors R 1R 2. This unit has been specially designed for hospitals and physiotherapy centers where the machine is required to run constantly for many hours to survive with the rush of patients.

With the protective resistance in the circuit, the potentiometer is balanced by means of the main dial and the slide wire. Supposing the value of emf of the standard cell is 1.