How to Calculate a Shunt

by Nachiket Deshmukh

A shunt is a high precision resistor that you can use to measure the current flowing through a circuit. According to Ohm's law, you can calculate the resistance of a shunt resistor by dividing the voltage drop across the shunt by current flowing through it. Shunt resistors are marked with power rating. Overheating of shunt resistors can result from a higher current flowing through them. Therefore, shunt resistance calculation is important in circuit design.


Write down the Ohm's law expression of "V = I * R" where "V" is the voltage drop across shunt resistor, "I" is the current flowing through shunt and "R" is the shunt resistance.


Substitute value of voltage "V" and current "I" in the Ohm's law expression. For example, if voltage across shunt is 10 volts and current flowing through it is 1 ampere, then the expression is 10 = 100 * R.


Divide the expression throughout by 100 to calculate the "R" value. Using a calculator, find the value of "R." From the example, the value of "R" will be 0.1 ohm, which is the value of shunt resistor.

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About the Author

Nachiket Deshmukh is a tech savvy professional with 11 years of experience in aerospace, engineering and IT industry. He is always on a lookout for low cost technology implementations for DIY home automation. Many of his articles have been published on eHow in personal finance and technology domains.