When it comes to circuit functionality many components play a role and one of them is a shunt resistor. Shunte resistors also function as a safety component to prevent damage to the circuit during voltage surges. But that is not their sole function and shunt resistors have other applications also. In this blog we will take an in-depth look at the shunt resistor and its applications and how to choose one for your project.
A shunt resistor is a kind of resistor that measures the current flow in a circuit. The shunt resistor should be connected in series with the circuit. The voltage across the resistor indicates the current flowing through a circuit.
Current measurement by using a shunt resistor is necessary in a circuit for various reasons. One vital reason to measure current flow is to confirm if the current is within the safe limit so that it does not damage the circuit components. Many issues can also be fixed within the circuit by current measurement through a shunt resistor. For instance, you can determine whether a current flow is sufficient for a particular component on the circuit. A lack of current means that the component is faulty.
Now, let's have a look at the shunt resistor applications
Safety Component Against Voltage Surge
High voltage surges can damage components of a circuit, and a large circuit, such as in your home, has many expensive electrical appliances that can be costly to repair or replace if damaged. A shunt resistor can be a safety component used to protect the circuit against voltage surge. This is done by a crowbar circuit, which consists of a shunt resistor. As the voltage gets high, the device short circuits, which immediately leads to a voltage drop. The shunt resistor is the key component that triggers the short circuit as it registers the high current.
Helps Bypass a Faulty Device in a Circuit
A fault in even one component attached in a circuit can break the current loop rendering the entire circuit non functional which shuts off all devices connected to the circuit. A shunt resistor is used to overcome this issue. The break in the current loop is avoided as the shunt will short circuit in he event of an excessive voltage and the electricity will bypass the faulty component.
Bypass Electrical Noise
In many electronic circuits high frequency noise can affect performance and lead to signal interference. A shunt resistor prevents the undesired signal from reaching the circuit components by redirecting the signal to the ground.
If you plant to include a shunt resistor in circuit design you must know about various shunt resistor specifications to select the right resistor. Following are the specifications to keep in mind.
Current Rating: Shunt resistors have a maximum current rating that is specified by the manufacturer. How much a voltage drops at the max current rating indicates the resistance value of the resistor. To illustrate, a shunt resistor that has a rating of 100 A and 50mV has a resistance value of 50/100 =0.5mΩ. After finding out the maximum current rating, you will be able to
Temperature Coefficient of Resistance (TCR): This is an important indicator of resistor performance. It is defines as change in resistance regarding ambient temperature. TCR values are essential for determining the suitable shunt resistor.
Power Rating: This is defined as maximum energy that a resistor can dissipate according to Joule’s Law. Large shunt resistors with a wide surface area have a higher power rating. If power dissipation exceeds the power rating of resistor than the shunt resistor will get damaged.
When choosing a shunt resistor, there are crucial parameters that must be taken into consideration including the resistance value, power rating, tolerance and temperature coefficient. It is, therefore, important that you comprehend the need of your circuit, the current measurement range you need and the accuracy that you require to measure the current to ensure that you find the best resistor that is reliable and meets the requirements of the circuit.
Further, considering the size, material and the way it is mounted will make it possible to complement with your circuit design. The implication, therefore, is that when you make an informed decision, you will be in a position to improve on the quality, speed and durability of the electrical projects that you undertake, and therefore, the outcomes that you are going to achieve.
