The SU Series delivers wirewound precision in a surface mount molded chip form factor designed for automated assembly. Low temperature coefficients and tight tolerances make these components ideal for high-density PCB layouts in instrumentation and precision analog circuits.

Dimensions & Suggested Land Patterns (per ANSI/IPC-SM-782 Guidelines)

S1, S2, S3 = Pedestal; S1/2 = None. All dimensions in inches.

Environmental Performance (KRL typical change)

Packing

Derating Curve

Derating varies by tolerance grade. SU models rated at 0.5% and above maintain full power to 85 °C; tighter tolerance grades (0.25%, 0.1%, 0.02%, 0.01%, 0.005%) derate at progressively lower temperatures.

PC and K Series resistors feature radial lead configurations for direct PCB insertion. These parts include derating guidance for tolerances below 0.1% and for elevated ambient temperature operation, making them well suited to test equipment and instrumentation where board-level precision is paramount.

PC Series — Round Body

K Series — Rectangular Body

† Indicates most popular types. All dimensions in inches. Power ratings at 125 °C ambient.

Derating Curve

PC and K Series resistors must be derated for tolerances below 0.1% and for elevated ambient temperatures. 1.0% and 0.5% tolerance grades maintain full power to 85 °C; tighter grades (0.25%, 0.1%) derate at progressively lower temperatures.

The HR Series Hermetically Sealed Precision Wirewound Resistors were designed for applications requiring the highest resistance stability possible. By combining the inherent stability of wirewound construction with extensive stabilization and a total moisture seal, the HR series offers a 3-year long-term stability specification of 0.0025% maximum. HR-Series resistors are typically used in high-accuracy instrumentation and as resistance standards.

HR-500 Series & HRK-300 Package Outlines

HR-500 Series (axial lead)

HRK-300 (printed circuit)

Specifications

All dimensions in inches. H dimension applies to HRK-300 (printed circuit style) only. Lead length: 1.5″ minimum.

Derating Chart

Tolerances of 0.02% and 0.01% maintain full rated power to approximately 100 °C. Tighter grades (0.005%, 0.0025%) derate at progressively lower temperatures. All grades derate linearly above their breakpoint to zero power at 145 °C.

The classic axial-lead precision wirewound resistors offer the highest accuracy and the best time and temperature stability in the KRL/Bantry catalog. The 500 Series provides 17 styles from 0.05 W to 2 W, with tolerances to ±0.005% and TCR to ±2 PPM. The EC Series offers an economy line with 6 styles from 0.25 W to 1.5 W. Both share a common operating range of −65 °C to +145 °C and are available with temperature-compensating TCRs from +80 to +6000 PPM, TC matching to ±0.5 PPM/°C, and a high-speed “H” prefix option for minimal reactance and fast rise time.

Package Outline (500 & EC Series)

Standard Temperature Coefficients

TCRs available to ±2 PPM/°C (25 Ω and above).

500 Series

EC Series — Economy Line

† Indicates most popular types. All dimensions in inches. Power ratings at 125 °C ambient.

Derating Curve

500 and EC Series resistors must be derated for tolerances below 0.1% and for elevated temperatures. The 1.0% and 0.5% grades maintain full power to 85 °C; tighter grades (0.25%, 0.1%, 0.05%, 0.02%, 0.01%, 0.005%) derate at progressively lower temperatures. The EC Series (dashed lines) has its own derating profile.

The workhorses of the KRL/Bantry power lineup. The AK “Space Miser” series provides compact power wirewound resistors from 1 W to 10 W. The P & C series extends the range with 20 styles from 0.5 W to 12 W, available in molded (P) and coated (C) construction. All power resistors operate with two derating curves — U and V — depending on mounting and heat-sinking conditions.

Package Outline (AK, P & C Series)

Lead length: 1.25″ minimum.

AK Series — Space Miser Power ResistorsNo longer available

P & C Series — Wirewound Power Resistors

P = Molded ( )    C = Coated. Dimensions in parentheses indicate P (molded) style where different from C (coated). All other dimensions in inches. U and V indicate derating curve; see chart below.

Derating Curve (P, C, and AK Series)

Curve U derates from 100% at 25 °C to 0% at approximately 225 °C. Curve V derates from 100% at 25 °C to 0% at approximately 350 °C. The applicable curve (U or V) is identified in the wattage columns of the tables above.

The NP Series uses a non-inductive winding construction for current sensing, power supply, and high-frequency applications where low inductance and low resistance values are critical. Available in standard 2-terminal (NP) and 4-terminal Kelvin-connection (NP4) configurations, with current ratings up to 26 A.

Package Outlines

NP Series (2-terminal)

NP(4) Series (4-terminal Kelvin)

NP Series — 2-Terminal Low-Ohm Power Resistors

NP(4) Series — 4-Terminal Kelvin Low-Ohm Power Resistors

All dimensions in inches. Wire diameter: .032 ± .002. Lead wire: 20 AWG. 4-terminal NP(4) styles separate voltage-sensing and current-carrying leads for Kelvin measurement.

NP Series Derating

NP Series resistors derate linearly from 100% at 25 °C to 0% at approximately 275 °C.

Robust ceramic-encased packages for high-power applications demanding superior heat dissipation, mechanical strength, and environmental protection. The CB and LB Series provide horizontal-mount ceramic boat resistors from 1 W to 22 W with current ratings up to 30 A. The V Series offers vertical-mount ceramic boat resistors from 2 W to 12.5 W.

CB & LB Series Package Outline

CB / LB Series (horizontal mount)

TF construction (thermal cutoff)

Ceramic Encased Boat Resistors — CB, LB Series

*20 AWG Style LB, 24 AWG Style CB   **18 AWG Style LB, 20 AWG Style CB. Higher custom Ω values available. All dimensions in inches. LB(4) lead length: 1.4″ minimum.

V Series — Vertical Mount Ceramic Boat Resistors

Note: Most of the above styles may be ordered with the following options: (F) for custom fusing action; (TF) for failsafe Thermal Fuse applications (see TF construction diagram above). All dimensions in inches. 20 AWG leads.

Temperature Rise & Derating

Diagram 1: Temperature Rise

Diagram 2: Derating

Diagram 1 shows temperature rise vs. percent rated load. Diagram 2 shows derating curves: Line A (OX & OXH Series) derates to 0% at ~225 °C; Line B (LB, CB, & V Series) derates to 0% at ~275 °C.

The SP and SL Series bring wirewound power and low-ohm capability into a surface mount molded chip package with UL94-V0 flammability rating. SP Series resistors cover 0.75 W to 3.5 W with resistance values up to 24 kΩ. SL Series resistors provide non-inductive, low-ohm performance from 0.5 W to 3 W with inductance below 7 nanohenries. Both are available with RoHS-compliant Pb-free construction and temperature-compensating TC values up to +6000 PPM/°C.

SP Series — Surface Mount Wirewound Power

SL Series — Surface Mount Low-Ohm Non-Inductive Power

Dimensions & Suggested Land Patterns (per ANSI/IPC-SM-782 Guidelines)

S1, S2, S3 = Pedestal; S1/2 = None. All dimensions in inches.

Environmental Performance (KRL typical change)

Packing

The FTS Series uses a four-terminal Kelvin connection to separate voltage-sensing and current-carrying terminals. This eliminates lead resistance errors and enables precision current measurement in power conversion, battery management, and motor control circuits. Two styles are available: the FTS-1 for higher resistance values (0.002 Ω to 0.05 Ω) with 18 AWG leads, and the FTS-2 / FTS-2L for ultra-low values (0.0005 Ω to 0.002 Ω) with heavy 12 AWG leads.

Specifications

Package Outlines

FTS Derating Curve

FTS Series resistors derate linearly from 100% at 25 °C to 0% at approximately 275 °C.

Precision wirewound construction with controlled positive temperature coefficients, available in any of the packages listed in the KRL catalog. Standard T.C. codes from A through T cover the most common requirements; custom T.C. values are available on request.

General Specifications

Temperature Coefficient Order Codes

† Indicates most readily available T.C.R.’s. All TCR values in PPM/°C. KRL will manufacture to any T.C.R. to meet customer specifications.

Power-rated resistors with controlled high TCR from +80 to +6000 PPM/°C, with a resistance range of 10 Ω to 25 kΩ. These have been widely adopted in power supplies, motor controllers, D/A and A/D converters, temperature sensors for medical electronics, aircraft systems, aerospace flight modules, and automotive electronic ignition systems. Available in any standard KRL power package.

General Specifications

Temperature Coefficient Order Codes

(1) KRL will manufacture to any T.C.R. to meet customer specifications. † Indicates most readily available T.C.R.’s. All TCR values in PPM/°C.