What is Shunt Resistor? + Function & Applications

What is Shunt Resistor?

What is Shunt Resistor? – An electric current, either alternating or direct, is measured using a shunt resistor. The voltage drop across the resistor is measured to accomplish this.

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What is a Shunt Resistor?

A shunt resistor (also known as a shunt) is a component that establishes a low resistance route in order to direct the majority of the circuit’s electrical current along this path. A shunt resistor typically consists of a material with a low-temperature coefficient of resistance, giving it very low resistance throughout a broad temperature range.

Ammeters, which are current-measuring instruments, frequently employ shunt resistors. The shunt resistance is linked in parallel in an ammeter. A device or circuit is linked in series with an ammeter.

What is Shunt Resistor?
A shunt resistor (Reference: uk.rs-online.com)

What is the Function of a Shunt Resistor?

The resistance of a shunt resistor is little. It is linked in parallel with a current measurement device and offers a low resistance channel for current.

The shunt resistor measures the current using ohm’s law. The shunt resistor’s resistance is known. Additionally, it is linked in parallel to the ammeter. The voltage is therefore the same.

Therefore, using the equation of ohm’s law below, we may determine the current flowing through the device if we measure the voltage across a shunt resistance.

Shunt Resistor for Current Measuring

An ammeter is a device used to measure electric current. The majority of contemporary ammeters gauge the voltage drop across an exact resistor with a known resistance. Using Ohm’s law, the current flow is calculated:


The majority of ammeters have a resistor built in to measure the current. A different arrangement is needed when the current is too high for the ammeter, though. The ammeter should be connected in parallel with a precise shunt resistor as a workaround. Ammeter shunt is a different name that is occasionally used to describe this sort of resistor.

Typically, this is a low resistance manganin resistor with excellent accuracy. Only a tiny (known) portion of the current passes through the ammeter due to the division of the current between the shunt resistor and the ammeter. The remaining current travels via the shunt resistor instead of the ammeter. Large currents may still be monitored in this manner. It is possible to measure the real amperage by properly scaling the ammeter. The maximum amperage that can theoretically be measured with this setup is limitless. However, the measuring device’s voltage rating must not be exceeded. This indicates that the maximum current cannot exceed the voltage rating when multiplied by the ammeter resistance value. To minimize circuit interference, the ammeter resistance value should also be as low as feasible. A smaller ammeter, however, results in a smaller voltage drop and a lesser resolution.

The Circuit’s Shunt’s Position for Measuring Current

The location of the shunt resistor in the circuit must be carefully chosen. The shunt is frequently positioned as near to the ground as is practical when the circuit and the measuring instrument share a common ground. The goal is to shield the ammeter from excessive common mode voltage that might harm the instrument or provide false readings. This configuration has the drawback that leakage currents that circumvent the shunt may go undetected. To safeguard the instrument, the shunt that is installed in the ungrounding leg must be isolated from the ground, have a voltage divider, or have an isolation amplifier. Other approaches are feasible, such as avoiding direct contact between the measuring device and the high voltage circuit by utilizing a Hall Effect sensor. However, modern shunts are frequently more cost-effective.

What is Shunt Resistor?
Position of the Shunt in the Circuit for Measuring Current (Reference: eepower.com)

What is a Shunt in Electronics?

The main objective of this article, which is to measure current, is to discuss shunt resistors. The term “shunt” has a larger connotation in the field of electronics, though. A shunt is a component that a circuit uses to reroute current around another component. There are many different applications. Electrical components other than resistors can be employed for various applications. A few instances are provided to highlight the variety of shunts.

Safeguarding a Circuit From Overvoltage

Using a crowbar circuit is one way to shield a circuit from excessive voltage. A short circuit will occur in a device if the voltage is too high. The current then flows parallel to the circuit as a result. The voltage in the circuit quickly drops as a result. A circuit breaker or a fuse should trip due to the excessive current flowing through the shunt.

Avoiding a Broken Gadget

In a series circuit, if one component fails, the entire circuit will be destroyed. This issue can be solved with a shunt. The shunt will short out due to the greater voltage that results from the failure. The faulty component will be sent around by the electricity. Lighting up for Christmas is a prime instance of this.

Avoid Electrical Hum

When high-frequency noise is a concern in a circuit, shunts with a capacitor may be used. The capacitor directs noise to the ground before the unwanted signal reaches the circuit components.

Applications of Shunt Resistors

The use of shunt resistors is described in the list below:

  • In an electrical circuit, a shunt resistor is utilized as overvoltage protection.
  • It is utilized in a gadget that measures current.
  • It is applied to get around broken equipment. (When several components are linked in series, if one fails to function, the circuit will be broken. Shunt resistor bypasses the malfunctioning component in this scenario and resumes the circuit route.)
  • To get around the high-frequency noise issue, a circuit uses a shunt resistor and capacitor.
  • It is utilized in power supply and overload protection control circuits.


FAQs about Shunt Resistors

1. What is the purpose of a shunt resistor?

An electric current, either alternating or direct, is measured using a shunt resistor. The voltage drop across the resistor is measured to accomplish this.

2. What do you mean by shunt resistance?

The slope of the dark current vs the applied voltage to the detector is known as shunt resistance (Rsh).

3. What is the difference between a shunt resistor and a normal resistor?

The temperature coefficient of thermal EMF is the primary distinction between shunt resistors and normal resistors. Normal resistors disregard the thermal EMF, whereas shunt resistors create a changing voltage based on the temperature of two distinct conducting materials.

4. Do I need a shunt resistor?

A resistor is usually included into ammeters to measure current. A different arrangement is needed when the current is too high for the ammeter, though. The ammeter should be connected in parallel with a precise shunt resistor as a workaround.

5. What is the two uses of shunt?

An electrical component known as a shunt produces a low resistance route in a circuit and permits electricity to flow through it. The amount of current passing through a shunt is measured using this device. Additionally, it serves as an overvoltage protection in circuits.

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