RTX Series Low Resistance Metal Film Chip Current Sensing Resistors
Low resistance metal film element on ceramic substrate
Power rating 1/8W to 2W across case sizes 0603, 0805, 1206, and 2512
Resistance range 45mΩ to 1000mΩ
Tolerance options ±0.5%, ±1%, ±2%, and ±5%
TCR ±75 ppm/°C for values 100mΩ and above; ±200 ppm/°C for 50mΩ to below 100mΩ; ±300 ppm/°C for values below 50mΩ
Operating temperature range −55°C to +155°C
Maximum rated current up to 4.47A depending on model and power rating
Short-time overload current up to 10A for 2512 package
Surface mount chip format — compatible with automated pick-and-place assembly
Supplied in tape and reel packaging; bulk case option also available
Lead-free, halogen-free, and RoHS compliant
What are the RTX Series Low Resistance Metal Film Chip Current Sensing Resistors?
The RTX is a surface-mount metal film chip resistor designed specifically for current sensing applications in the milliohm resistance range. The metal film resistive element is deposited on a ceramic substrate and trimmed to value, combining the low-inductance characteristics of a planar film construction with the dimensional precision of a standard SMD chip package. Four case sizes are available — 0603 (RTX03), 0805 (RTX05), 1206 (RTX06), and 2512 (RTX25) — spanning power ratings from 1/8W up to 2W and providing a selection of footprint and power-handling options to suit different board layout and current-level requirements.
Resistance values cover 45mΩ to 1000mΩ, with the usable range for each model depending on case size and the desired tolerance grade. The tightest tolerance option of ±0.5% is available across the main resistance range, with ±1%, ±2%, and ±5% grades also offered for applications where cost rather than accuracy is the primary constraint. TCR is ±75 ppm/°C for resistance values of 100mΩ and above, rising to ±200 ppm/°C in the 50mΩ to below-100mΩ range and ±300 ppm/°C for the lowest values below 50mΩ available on the 1206 package. The ±75 ppm/°C grade is particularly well-suited to applications where component self-heating under continuous load would otherwise cause resistance drift significant enough to affect current measurement accuracy.
The metal film construction produces a resistive element with low residual inductance, making the RTX series suitable for use in switching power converters and pulse-width-modulated drive circuits where wirewound shunt alternatives would introduce reactive impedance at the switching frequency. Rated current handling ranges from 1.58A continuous for the lower power 0805 variants up to 4.47A for the 2W-rated 2512 package, with short-time overload current ratings extending to 10A for the largest case size — providing margin against the transient currents present at start-up or during load steps without resistance degradation. The 5× overload rating (applied for five seconds) produces a resistance shift of no more than ±1.0%, confirming the robustness of the metal film element under fault-level stress.
The RTX series is qualified to the JIS C 5201 and JIS C 5201-1 test standards, covering thermal shock between −55°C and +150°C over 300 consecutive cycles, 1000-hour damp heat load life at 85°C and 85% relative humidity, 1000-hour load life at 70°C, and vibration across 10 Hz to 55 Hz in three axes. Resistance change in all of these tests is held to ±1.0% or better, confirming the stability of the metal film element under prolonged electrical and environmental stress. All RTX variants are lead-free and halogen-free, meeting RoHS requirements, and are supplied in standard 4 mm pitch carrier tape and reel packaging for direct use with automated assembly equipment.
RTX Series Low Resistance Metal Film Chip Current Sensing Resistors Specifications
A practical overview for engineers and procurement teams evaluating resistive solutions.
Model: RTX
Resistor type: Current Sensing
Description: Chip
Power Rating: 1/8W~2W
Resistance (Ω): 50m~1000m
Tolerance (%): ±0.5, ±1, ±2, ±5
TCR (ppm/C): 75-300
Applications of the RTX Series Low Resistance Metal Film Chip Current Sensing Resistors
Where RARA metal clad resistors are deployed in the field.
Motor drive and inverter phase current feedback — series shunt measurement in variable frequency drives, servo amplifiers, and brushless DC motor controllers, where the RTX chip resistor provides the current feedback signal for torque control, speed regulation, and overload protection across the full motor current range.
Switch-mode power supplies and DC-DC converters — output current sensing for current-mode control loops, overcurrent protection, and regulation feedback in compact switching converter designs, where the low-inductance metal film element avoids the switching noise coupling that wirewound shunts can introduce.
EV battery management systems — charge and discharge current monitoring in electric vehicle battery management units and on-board charger circuits, where the ±0.5% tolerance and ±75 ppm/°C TCR grades deliver the measurement accuracy required for reliable state-of-charge calculation across the vehicle’s operating temperature range.
UPS and power conditioning equipment — load current measurement and overload detection in uninterruptible power supply systems and power conditioners, where the 2W-rated 2512 package handles the higher continuous currents typical of UPS output stages in a standard SMD chip footprint.
Industrial automation and control systems — current sensing in programmable logic controller output modules, relay driver circuits, solenoid drive stages, and embedded industrial controllers requiring a compact, solderable current measurement element within a high-density board layout.
Solar inverters and renewable energy systems — continuous-duty current measurement in solar inverter power stages and battery energy storage system converters, where the wide operating temperature range of −55°C to +155°C and stable load life performance suit outdoor and thermally variable installation environments.
Telecommunications power equipment — current monitoring in DC power distribution units, rectifier modules, and base station power supplies, where the tape and reel packaging supports high-volume automated assembly of power supply boards in telecommunications infrastructure equipment.
Automotive electronics — current sensing in DC-DC converters, on-board chargers, and body electronics modules within automotive systems, where the −55°C to +155°C operating temperature range covers the full automotive ambient specification and the lead-free RoHS-compliant construction meets automotive environmental requirements.
Test and measurement instruments — precision shunt elements in electronic loads, power analysers, and benchtop power supplies, where the tight ±0.5% tolerance and low TCR of the RTX series provide a stable and repeatable current measurement reference across the instrument’s operating temperature range.
Related Products of the RTX Series Low Resistance Metal Film Chip Current Sensing Resistors
Model: CS
Resistor type: Current sensing
Description: Chip
Power Rating: 1/20W~3W
Resistance (Ω): 1m~8000m
Tolerance (%): ±1, ±2, ±5
TCR (ppm/C): 100, 1000
Model: CSTN
Resistor type: Current sensing
Description: Chip
Power Rating: 1/16W~3W
Resistance (Ω): 50m~1000m
Tolerance (%): ±0.5, ±1
TCR (ppm/C): 50, 100, 200
Model: RS
Resistor type: Current sensing
Description: Thick film chip
Power Rating: 1/16W~2W
Resistance (Ω): 10m~976m
Tolerance (%): ±1, ±5
TCR (ppm/C): 200, 1500
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.
