Electronic circuit design and repair, diversionresistance(Shunt Resistor) is a very important component, mainly used to detect the size of the current, and obtain the current value indirectly by measuring the voltage drop across its ends. Properly identifying and measuring shunt resistors is critical to ensuring the proper and safe operation of the circuit. This article will introduce in detail the definition and function of shunt resistors and how to accurately find shunt resistors, helping electronics enthusiasts and engineers improve their circuit analysis capabilities.
1. What is a shunt resistor?A shunt resistor is aLow value resistor, usually installed on the current path in a circuit, to produce a voltage drop proportional to the current. By measuring the voltage across the shunt resistor, the amount of current flowing through it can be calculated. Because its resistance is extremely small, generally between a few milliohms and tens of milliohms, the purpose is to minimize the impact on the circuit.2. Common locations of shunt resistorsIn power management, battery protection, motor drive and other circuits, shunt resistors are often set on the ground side or power side of the current loop. Common locations include:Between battery negative terminal and groundBetween power input terminal and load
Current detection terminal of motor drive circuit
3. Find the shunt resistor through the circuit diagramThe most direct way is to look at the circuit schematic. The shunt resistor is usually marked as a low-resistance resistor with the symbol "R" and number. Generally, there will be clear resistance labels, such as 0.01Ω, 0.05Ω, etc. The location of the shunt resistor can be quickly located through the schematic diagram.4. Identify the appearance characteristics of the shunt resistorShunt resistors are mostly metal film resistors or metal strip resistors, which are large in size and have extremely low resistance. Their appearance is different from ordinary resistors. They are usually thicker and have metal pins. Some high-power shunt resistors also have heat sinks. You can also determine whether it is a shunt resistor by looking at the resistance mark (such as "0.01Ω").5. Use a multimeter to measure the shunt resistanceIf there is no circuit diagram or identification, you can use the ohms setting of a multimeter to measure the resistance of the resistor. Shunt resistors have extremely low resistance, typically in the milliohm range, which requires a high-precision multimeter or specialized low-resistance measuring instrument. When measuring, it is necessary to turn off the power and disconnect the circuit at both ends of the resistor to avoid measurement errors.6. Judgment by current detection circuitThe shunt resistor is usually connected to the input end of the current detection module. If there is a current sampling chip or op amp circuit in the circuit, the shunt resistor is usually near its input end. Observing the circuit layout of this part will help to find the shunt resistor.7. Pay attention to the power rating of the shunt resistorSince the shunt resistor is responsible for the current detection task, it often needs to withstand large power. The power level is generally higher, with 0.5W, 1W or even higher being common. The power mark and size can also assist in identification.：As a key component of current detection, the shunt resistor's accurate identification is extremely important for circuit debugging and troubleshooting. The shunt resistor can be effectively found by looking at the circuit diagram, observing the appearance characteristics, measuring with a multimeter, and combining the layout of the current sensing circuit. Understanding the functions and characteristics of shunt resistors can help electronic engineers better understand the working principles of circuits and improve maintenance efficiency. I hope this article’s detailed explanation of “How to find a shunt resistor” can provide valuable reference for your electronic learning and practice.
