Table of Contents
A Basic DC Potentiometer, Key features of potentiometers are, Operation of the DC Potentiometer
A potentiometer is a device that measures the potential difference between two terminals of a circuit or network with known properties or across a known resistance. The emf of two cells can also be compared using a potentiometer. A potentiometer is frequently used in measurements when a higher level of precision is needed than is typically possible with deflecting instruments, when no current needs to be drawn from the source being tested, or when the current needs to be kept to a minimum.
A potentiometer can measure current by observing the voltage drop caused by an unknown current flowing through a known standard resistance because it measures voltage by comparing it to a standard cell. Power can also be calculated with a potentiometer, and if time is also measured, energy can be calculated by summing the two. A potentiometer is one of the key tools for electrical measurements as a result.
Key features of potentiometers are
- Instead of measuring the actual pointer deflection, a potentiometer compares the unknown voltage to a known voltage source. It also guarantees a high level of accuracy.
- A potentiometer doesn’t require any power because it measures under the null or balance condition.
- Potentiometer voltage measurement is largely independent of source resistance.
A Basic DC Potentiometer
Take a look at the basic dc potentiometer circuit diagram below:
Operation of the DC Potentiometer
First, the switch S is put in the ‘operate’ position and the galvanometer key K is kept open,. The slide wire and rheostat receive their working current from the battery. By altering the rheostat setting, the working current through the slide wire may be changed. Finding a position for the sliding contact such that the galvanometer displays zero deflection, or indicates null condition,. When the galvanometer key K is closed is necessary for measuring the unknown voltage E1. The unknown voltage E1 is assumed to be equal to the voltage drop E2 across position a-c of the slide wire by zero galvanometer deflection. It is now necessary to assess the voltage drop E2 along the slide wire’s portion a-c in order to determine the values of the unknown voltage.
When the switch S is placed at ‘calibrate’ position a standard or reference cell is connected to the circuit. The potentiometer is standardized using this reference cell. The slide wire has a uniform cross-section, which also means that its resistance is uniform the entire way through. To accurately position the potentiometer sliding contact along the slide wire at any desired location,. A calibrated scale in centimeters and fractions of centimeters is placed along the slide wire. By adjusting the working current values, the voltage drop along the slide wire can be controlled. Because the resistance of the slide wire is precisely known. ‘Standardization’ is the process of adjusting the working current to match the voltage drop across a section of sliding wire against a standard reference.