Method of Measuring Low Resistance
Sudarshan Ghane
Posted on May 23, 2025
Measurement of Low Resistance
Motivation - When you go to the dairy, ask for 250 ml of milk and also for 500 ml of milk. The dairy owner used a small gauge to measure the 250 ml of milk and a larger gauge for the 500 ml. Notice that a smaller instrument was used for the smaller quantity, while a different, larger instrument was used for the larger quantity.
Now in this lesson you learn about the how measure low resistance and high resistance. Which instrument used for measuring low resistance and high resistance.
Following type of Method are used measure low resistance.
- Voltmeter and Ammeter Method
- Kelvin Bridge
- Shunt type ohmmeter
Voltmeter and Ammeter Method
A voltmeter is an instrument used to measure the voltage in a circuit, in volts, while an ammeter is used to measure the current in a circuit, in amperes. The voltmeter is always connected in parallel with the circuit, whereas the ammeter is connected in series with the circuit.
To perform the measurement, you need the following components: a voltmeter, ammeter, power supply, connecting wires, and a fuse.
As shown in the circuit diagram, the power supply is connected to the circuit. A switch is connected in series; when the switch is turned on, current flows through the circuit. Take readings from both the ammeter and voltmeter, and use the formula:
R = Voltmeter Reading / Ammeter Reading
This will give you the value of the resistance.
Medium resistance is typically measured using instruments like the Kelvin Bridge or Wheatstone Bridge.
High-voltage cables have insulation resistance. To measure high resistance, use a megohmmeter or Megger.
Ohmmeter Method
An ohmmeter is an instrument used to measure resistance. There are two types:
- Series-type ohmmeter: Used to measure medium resistance.
- Shunt-type ohmmeter: Used to measure low resistance.
Important Note: Before using an ohmmeter in a circuit, make sure the circuit is switched off and any electrolytic capacitors are fully discharged
