Current sensing resistor is a very low resistance used to measure the current flowing through it. The current through the resistor is represented by the voltage on the resistor, so by applying the I=V/R set by renowned teacher Georg Simon Ohm, the current is proportional to the voltage on the resistor. A brief introduction to this topic is the core content of the rest of this article. The topics involved here - resistance selection, high or low voltage side monitoring, and selecting a sensing amplifier - are all based on this basic electrical engineering formula, and Hall DC sensors are a different choice from sampling resistors.

The current perception monitoring helps improve the efficiency of certain systems and reduce losses. For example, many mobile phones have implemented current sensing to monitor and improve battery life, while also enhancing reliability. If the current consumption is too high, the phone can decide to lower the CPU frequency to reduce battery load, thereby extending battery life and preventing the phone from overheating, thereby improving reliability. Even mobile applications can access current read-write circuits and make decisions to optimize phone performance. In addition to using resistors for current detection, two other less common methods were also employed. One method is to use Hall effect sensors to measure the magnetic field generated by current, which is the Hall DC sensor. Although this is non embedded and has the advantage of no insertion loss, it is a bit expensive and requires a relatively large PCB board. Another method is to measure induced AC current using a transformer, which has a high size and cost, but is only suitable for AC current.