The most popular method for measuring low resistance is the Kelvin double bridge method. This method is widely used because it provides high accuracy and eliminates errors caused by lead resistance and contact resistance.

1. Kelvin Double Bridge Method:
The Kelvin double bridge method is based on the Wheatstone bridge principle. It is specifically designed to measure low resistances accurately. This method uses a four-arm bridge circuit, where one arm consists of the unknown resistance and three arms consist of known resistances.

2. Principle of Operation:
The principle behind the Kelvin double bridge method is to eliminate the effects of lead resistance and contact resistance. These resistances can introduce significant errors when measuring low resistances.

In this method, a current is passed through the unknown resistance using a constant current source. The voltage drop across the unknown resistance is measured using two sets of terminals. One set of terminals is used to pass the current through the unknown resistance, while the other set is used to measure the voltage drop across the resistance.

3. Advantages of Kelvin Double Bridge Method:
The Kelvin double bridge method offers several advantages, making it the most popular method for measuring low resistance:

- Eliminates lead resistance: The four-terminal configuration of this method allows for separate current and voltage measurement terminals, eliminating the influence of lead resistance.

- Minimizes contact resistance: By using precise and low-resistance contacts, the Kelvin method reduces errors caused by contact resistance.

- High accuracy: The elimination of lead and contact resistance ensures high accuracy in resistance measurement.

- Wide measurement range: The Kelvin method can measure resistance values ranging from micro-ohms to kilo-ohms.

- Precise current source: A constant current source is used to ensure accurate measurement and minimize errors.

4. Applications:
The Kelvin double bridge method is extensively used in various industries and applications, including:

- Electrical power transmission and distribution systems: It is used to measure low resistance in power cables, busbars, and grounding systems.

- Electronic circuit testing: It is employed to measure resistance in PCB traces, connectors, and other electronic components.

- Material testing: It is used to determine resistivity and conductivity in materials such as metals, alloys, and conductive coatings.

- Battery testing: It is utilized to measure internal resistance in batteries.

In conclusion, the Kelvin double bridge method is the most popular method for measuring low resistance due to its ability to eliminate lead resistance and contact resistance, providing high accuracy and reliability in resistance measurements.