PCSK/PCSR Series Current Sensing Resistors

RESI's PCSK and PCSR series are made from precision nickel-chrome alloy, which are then precisely machined and welded using exclusive electron beam (EB) welding equipment. The series are molded versions that can achieve ultra-low temperature coefficient of resistance (TCR) within ±15 ppm/°C and ±25 ppm/°C and high tolerances up to ±0.1% and ±0.5%, respectively. With an operating temperature range of -65°C to +170°C, the series are ideal for current sensing circuits requiring high precision and low TCR simultaneously. High-precision, 2512-size current sensing resistors offer excellent stability and low temperature coefficient of resistance (TCR) in applications such as instrumentation, semiconductor assembly and tests, sorting and formation of lithium-ion batteries, and precision power supplies. The value range is from 5 mΩ to 100 mΩ, the tight tolerance is ±0.1%, and TCR is down to ±15 ppm within the whole value range. The PCSK series is an economical version that also reaches ±0.5% tolerance and TCR of ±25 ppm.

The resistor alloy and EB welding quality greatly influence the performance of the PCSK and PCSR series. This variety of current sensing resistors is formed by welding Ni-Cr alloy with a copper electrode. The electron beam melts through the welding joint to weld two dissimilar metals. Ni-Cr alloy has a high resistivity and low TCR that can be adjusted by the heat treatment process. RESI has been developing more advanced treatment processes to improve material stability. The resistors based on the EB welding have high requirements for the welding process. Unstable power during welding causes uneven welds and poor welding performance. The quality of electron beam welding influences tolerance the most. RESI’s independently developed EB welding machine can reach depth-to-width ratio of up to 20:1, a very narrow welding heat-affected zone. Additionally, the highly autonomous EB welding process with a maximum welding speed of 20 m/min can guarantee capability and timely delivery.