The RSNB series is a current-sensing resistor built around an all-metal bridge-shaped element, formed from a manganese copper or Karma alloy strip joined to pure red copper terminals by vacuum electron-beam welding. This all-metal construction, together with a surface pickling and passivation treatment, gives the RSNB series strong resistance to weathering and mechanical stress, while the bridge shape lifts the resistive element clear of the mounting surface to aid heat dissipation and support high pulse loads. Because the element is formed rather than wound, and because current flows through a short, direct metal path between terminals, the RSNB series exhibits ultra-low parasitic inductance and ultra-low thermal EMF, giving it a fast response that suits high-frequency AC current detection as well as DC current sensing.
Two models make up the series. The RSNB4312 is rated at 4W and is offered in manganese copper values of 2mΩ, 3mΩ, 5mΩ and 10mΩ and a Karma value of 20mΩ. The RSNB4320 is rated at 7W and is offered in manganese copper values of 1mΩ and 2mΩ and Karma values of 5mΩ, 6mΩ, 8mΩ and 10mΩ. Both models are available in ±1% and ±5% tolerance, with a temperature coefficient of resistance of ±100ppm/°C for the manganese copper elements and ±50ppm/°C for the Karma elements, and both share a parasitic inductance below 3nH, a thermal EMF of less than 1μV/°C over 0-100°C, and an operating temperature range of -55°C to +170°C. The rated power of both models follows a derating curve that holds 100% of rated power up to 70°C ambient before linearly reducing to zero at 170°C.
Physically, the RSNB4312 and RSNB4320 share a common length and height of 11mm and 3.3mm respectively, and a common terminal spacing of 4mm, with the RSNB4312 measuring 3.15mm in width and the RSNB4320 measuring 6.2mm in width to accommodate its lower resistance values. Resistor traces are laser-precision trimmed to bring each part to its specified resistance value. The series is qualified to IEC60115-1 test methods covering temperature coefficient of resistance, solderability, short-time overload, resistance to soldering heat, high-temperature and humidity exposure, high-temperature storage, low-temperature load, temperature cycling and load life, and is AEC-Q200 qualified and RoHS compliant. Parts are supplied on 13-inch reels for 24mm tape, in quantities of 2,000 pieces per reel for the RSNB4312 and 1,000 pieces per reel for the RSNB4320.
