Current sense resistors, or shunts, are used to gauge the flow of current whilst minimally reducing it by measuring the voltage drop across a low value resistor.

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The proportional relationship between voltage and current according to Ohm’s Law enables a sensor circuit to measure the amperes delivered to a load in real-time.  This is a simple and cost-effective method of current flow measurement and is used to mitigate the effects of short-circuits or overloads and to maximize the efficiency of electrical systems. However, there are considerations to bear in mind when it comes to measuring current flow with a current sense resistor.

In this blog post, TT Electronics outlines the basics of current sense resistors in greater depth.

Current Sense Resistors: The Basics

Current sense resistors are generally positioned in-line on the conduction path between the power source and the load in an IC or PCB. The part is generally engineered for extremely low resistance values to minimise the voltage drop and the power loss. Typical resistance values for current sense resistors fall on the milliohms scale.

The underlying theory of current sense resistors follows the working principles of standard electrical resistors. However, while a standard resistor is primarily used to regulate current, a current sense resistor is used for monitoring purposes. They are often connected to amplifiers to minimize the impact of noise while maintaining accurate levels of resolution. Where the subsequent circuitry is at a different voltage from the current path, an isolation amplifier is used. This is not a mandatory configuration but choosing between isolated and non-isolated current sense resistors is an important question to pose when designing a current flow measurement system.

Voltage drop is a critical metric to bear in mind when choosing a current sense resistor. Interposing the current sense resistor between the supply and the load will cause some measure of power dissipation due to the voltage drop as the current passes through the resistor. This constitutes wasted power that does not reach the load and is instead dissipated as heat, which can further impact the performance of the device. We explored this challenge in detail in a previous post: How to choose and use a current-sense resistor.

Current Sense Resistors from TT Electronics

TT Electronics is one of the world’s leading suppliers of precision electrical components. We have supplied cost-effective, RoHS compliant current sense resistors for an extensive range of applications, furnishing engineers in a range of electronics sectors with effective solutions for current flow measurement.

If you would like to learn more about our current sense resistors, please do not hesitate to contact us directly.


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