RMF Series High Power Four-Terminal Precision Current Sensing Resistors
High-power precision resistor with four-terminal (Kelvin) connection
Rated power 10W at 70°C; derated linearly to zero at 170°C
Resistance range 0.5mΩ to 200mΩ
Tolerance options ±0.1%, ±0.5%, ±1%, ±2%, and ±5% depending on resistance sub-range
TCR options ±5, ±10, ±15, ±20, and ±30 ppm/°C
Low inductance — less than 5μH measured at 1 MHz
Operating temperature range −65°C to +170°C
Short-time overload rated at 5× power for 5 seconds; 2.5× power for 10 seconds on lowest resistance values
ESD rated to ±6 kV direct contact and up to ±25 kV air discharge
RoHS compliant
What are the RMF Series High Power Four-Terminal Precision Current Sensing Resistors?
The RMF is a high-power precision resistor designed for current sensing applications where the combination of low resistance, high accuracy, low temperature coefficient, and four-terminal Kelvin connection is required in a single component. Rated at 10W continuous power at 70°C with a linear derating curve extending to 170°C, the RMF bridges the gap between standard milliohm chip shunts and large panel-mounted precision shunts, providing usable power handling in a compact package without sacrificing the measurement accuracy that current-sensing circuits demand. The resistance range spans 0.5mΩ to 200mΩ, covering the low-impedance values needed when a shunt must pass substantial continuous current while generating only a small sense voltage.
The four-terminal Kelvin connection is the defining constructional feature of the RMF. In a conventional two-terminal shunt, the voltage sensed by the measuring circuit includes the resistance of the current-carrying leads and solder joints as well as the resistive element itself — an error that becomes significant as resistance values drop below a few milliohms. The Kelvin arrangement separates the current path from the sense path: two terminals carry the load current through the element, and two independent sense terminals connect directly to the resistive element at points upstream of the current terminals, ensuring that no lead or contact resistance appears in the voltage measurement loop. This connection method allows the RMF to maintain its stated tolerance across the full milliohm resistance range, down to the lowest values where two-terminal measurement would be unreliable.
Tolerance options range from ±0.1% for the highest resistance values (51mΩ to 200mΩ) down to ±1%, ±2%, and ±5% for the lower sub-ranges where tighter manufacture is more demanding, with ±0.5% and ±1% available at the mid-range. TCR is selectable from ±5 ppm/°C through to ±30 ppm/°C, allowing the designer to choose the appropriate balance between measurement stability over temperature and component cost. The low inductance specification of less than 5μH at 1 MHz confirms that the RMF element is suitable for use in switching and pulsed environments where a wirewound shunt of equivalent resistance and power rating would introduce unacceptable inductive reactance.
Environmental and electrical reliability is confirmed across a comprehensive qualification programme. Temperature cycling across 1000 cycles between −55°C and +150°C, thermal shock across 1000 cycles over the same range, 1000-hour biased humidity exposure at 85°C and 85% relative humidity, and 1000-hour operational life at rated power and 125°C ambient all produce a resistance change of no more than ±0.5%. ESD immunity is qualified to ±6 kV by direct contact discharge and up to ±25 kV by air discharge, and short-time overload at five times rated power for five seconds is also held within ±0.5% resistance change. The complete qualification confirms the RMF as suitable for demanding industrial and precision measurement applications where long-term resistance stability under both electrical and environmental stress is a prerequisite.
RMF Series High Power Four-Terminal Precision Current Sensing Resistors Specifications
A practical overview for engineers and procurement teams evaluating resistive solutions.
Model: RMF
Resistor type: Precision
Description: High power 4 terminal
Power Rating: 10W
Resistance (Ω): 0.5~200
Tolerance (%): ±0.1~±5
TCR (ppm/C): 5, 10, 15, 20, 30
Applications of the RMF Series High Power Four-Terminal Precision Current Sensing Resistors
Where RARA metal clad resistors are deployed in the field.
Precision current measurement instruments — four-terminal Kelvin shunt elements in benchtop and portable current meters, precision power analysers, and electronic calibrators where lead resistance exclusion and tight tolerance are mandatory for traceable current measurement accuracy.
EV battery management systems and coulomb counting — high-accuracy charge and discharge current monitoring in electric vehicle battery packs and on-board charger systems, where the low TCR grades (±5 to ±15 ppm/°C) maintain measurement accuracy across the full battery operating temperature range and the 10W power rating accommodates the continuous currents present in high-voltage EV battery circuits.
Motor drive and inverter current feedback — precision phase current sensing in high-performance servo amplifiers, variable frequency drives, and brushless motor controllers, where the four-terminal connection eliminates contact resistance error and the low inductance element avoids distortion of the current waveform at drive switching frequencies.
Power supply and DC-DC converter regulation — high-accuracy output current sensing for current-mode control loops in switching power supplies and high-current DC-DC converters, where the ±0.1% tolerance and low TCR support tight current regulation and consistent overcurrent threshold setting across temperature.
Industrial power metering and energy monitoring — precision shunt elements in revenue-grade and sub-metering energy meters, power quality analysers, and industrial energy management systems, where the Kelvin connection and low TCR deliver the measurement accuracy required for billing-grade current measurement at sustained high-current levels.
Test and measurement equipment — reference shunt resistors in electronic loads, source measure units, and laboratory power supplies where the four-terminal construction, ±0.1% tolerance, and ±5 ppm/°C TCR provide the stable, well-characterised resistance needed as a calibration-traceable current reference element.
UPS and power conditioning systems — high-power current sensing in uninterruptible power supply output stages and active power conditioning equipment, where the 10W rating and wide operating temperature range handle the continuous load currents of industrial UPS installations without requiring an external heatsink or forced air cooling.
Renewable energy inverters and storage systems — precision current measurement in solar inverter DC input stages and battery energy storage system power converters, where continuous-duty operation across wide ambient temperature swings and the need for accurate energy accounting favour the low TCR and high-power Kelvin shunt format of the RMF.
Automotive and transportation power electronics — high-accuracy current sensing in DC-DC converters, traction inverters, and charging infrastructure equipment, where the −65°C to +170°C operating temperature range, ESD robustness, and RoHS compliance address the combined electrical, environmental, and regulatory requirements of automotive and transit power electronics applications.
Related Products of the RMF Series High Power Four-Terminal Precision Current Sensing Resistors
Model: AH
Resistor type: Current sensing
Description: Four terminal precision
Power Rating: 3W, 10W
Resistance (Ω): 1m~100
Tolerance (%): ±0.1, ±5, ±1
TCR (ppm/C): 10
Model: PCR4T
Resistor type: Current sensing
Description: Through Hole
Power Rating: 3W
Resistance (Ω): 1m-10m
Tolerance (%): ±0.5, ±1, ±5
TCR (ppm/C): 30
Model: HPCR4T
Resistor type: Current sensing
Description: Through Hole
Rated Current: 35-65A
Resistance (Ω): 0.5m-4m
Tolerance (%): ±0.5, ±1
TCR (ppm/C): 30
Model: PBV, PBH
Resistor type: Current sensing
Description: Four terminal precision
Power Rating: 3W, 10W
Resistance (Ω): 0.5m~100m
Tolerance (%): ±0.5, ±1, ±5
TCR (ppm/C): 30, 50
Why Choose RARA Current Sensing Resistors
What sets RARA apart for engineers and procurement managers in industrial and automotive markets.
01
8 Sub-Categories
No other single supplier covers AEC-Q200 chip shunts, milliohm precision types, four-terminal Kelvin shunts, power metering, and 12,000A panel shunts under one ISO-certified roof.
02
Extreme Precision
HPS, UHPS, and PSS precision shunts deliver ±0.05% tolerance and 3 ppm/°C TCR — meeting the accuracy demands of EV battery coulomb counting, precision power analyzers, and billing-grade energy metering.
03
Automotive Qualified
Multiple AEC-Q200 certified models (BCS, LRA, ECS, BWR, TCS, PCBS) with IATF 16949 manufacturing certification — covering EV battery management, motor control, and charging applications.
04
Global Track Record
Trusted by Tesla, GM Korea, Proterra, Siemens, Rockwell, and Schneider Electric — deployed in EV powertrains, industrial drives, and utility metering systems across six continents.
