What made you select the Ohmite FK/GK and FC4L Series 4-Terminal Current Sense Resistors as a featured product?
I chose the Ohmite 4-terminal current sense resistors because their Kelvin connection design helps eliminate a critical source of measurement error in high-current power systems: the parasitic resistance introduced by terminations, solder joints and PCB traces. Unlike conventional 2-terminal resistors, which use the same terminations to carry current and measure voltage, the FK/GK and FC4L series provide separate current-carrying and voltage-sensing terminals. This allows engineers to measure the voltage drop directly across the resistive element while minimizing the influence of interconnect resistance. That distinction is especially important in precision current-sensing applications, including automotive power electronics, industrial motor drives, frequency converters, power modules and battery management systems, where accurate current feedback is essential for control, efficiency and overcurrent protection.
In these applications, even small measurement errors can significantly affect system performance. At milliohm-level resistance values, a few hundred microohms of parasitic resistance can introduce substantial error into a conventional 2-terminal measurement. Designers must also account for temperature-dependent resistance changes, self-heating and high-current PCB layout constraints. A 4-terminal sensing architecture addresses the interconnect-related measurement error, while low-TCR resistive materials and robust construction help maintain measurement accuracy across changing operating conditions.
The Ohmite FK/GK and FC4L series offer two approaches to low-resistance, 4-terminal current sensing, with construction and mounting options suited to different power system requirements.
Specification | FK/GK Series | FC4L Series |
Construction | Metal alloy chip | Metal foil, Ni-Cu-Mn |
Connection | 4-terminal Kelvin | 4-terminal Kelvin |
Power rating | Up to 5 W | Up to 5 W |
Resistance | 0.3mΩ – 3mΩ | 1 mΩ – 500mΩ |
Key advantage | Long-term stability | Low TCR and stable current |
Design focus | High-power current | Precision current sensing and |
The FK/GK series combines low-resistance metal alloy construction with excellent long-term stability and compatibility with direct copper bonded (DCB) and insulated metal substrate (IMS) assemblies. This makes it particularly useful in high-current power modules where thermal management, compact packaging and reliable current feedback are important.
The FC4L series uses a nickel-copper-manganese (Ni-Cu-Mn) resistive element to achieve a low temperature coefficient of resistance, helping limit current measurement drift as operating temperatures change. Its integrated 4-terminal design features two larger terminals to carry the load current and two dedicated sense terminals for precise voltage measurement across the resistive element. With resistance values down to 1 mΩ, power ratings up to 5 W and construction designed for automated SMT assembly, the FC4L series is well suited for precision sensing in compact, high-current PCB designs.
What are the key features/specifications of the Ohmite 4-Terminal Current Sense Resistors?
Key Features
- 4-terminal Kelvin connections: Separate current and voltage paths minimize measurement errors associated with termination, solder joint and PCB trace resistance.
- Low-resistance construction: Supports current sensing with minimal shunt voltage drop and reduced power loss compared with higher-resistance sensing elements.
- Power ratings up to 5 W: Accommodate current measurement in demanding power electronics applications, subject to thermal design and derating requirements.
- Stable resistive materials: Metal alloy and metal foil construction support low TCR values for consistent sensing over temperature ranges.
- Flexible integration: FK/GK devices support DCB/IMS substrate mounting, while FC4L devices are designed for automated PCB assembly.
- Long-term reliability: Robust construction helps maintain consistent current measurement over extended operation lifetimes.
What are some common markets/applications of the Ohmite FK/GK and FC4L Series 4-Terminal Current Sense Resistors?
Target Markets & Applications
- Automotive power electronics and e-mobility systems
- Battery management systems and energy storage
- Industrial motor drives and frequency converters
- High-current power modules and hybrid power circuits
- Renewable energy power conversion systems
- Industrial and automatic control power supplies
- Data center and telecommunications power systems
