Global trends such as the demand for lower CO2 emissions, intelligent electricity supply grids and automotive electrification drive the need for more efficient electronic circuits. Essential, therefore, is to understand what level of current is flowing through a circuit and being delivered to a load. Maximizing the operating performance of a battery, controlling motor speeds, and the ability to hot swap server units can all benefit from the use of accurate current measurement. This paper presents how current sense resistors work and why they are optimal, low-cost solutions that help OEMs create more efficient circuit designs in a wide range of applications.