CSM Series Resistors

VPG Foil Resistors announced that it has enhanced the CSM series of ultra-precision, surface-mount, current-sensing resistors in the compact 2512 and 3637 case sizes. The improved devices offer a standard TCR of ± 15 ppm/°C max. (-55°C to 125°C, 25°C ref.), with ± 10 ppm/°C max. available on request, and an extended resistance range down to 1 mΩ.

The CSM features a low thermal electromotive force (EMF) that is critical in many precision applications. The device’s all-welded construction is composed of a Bulk Metal® resistive element with welded copper terminations, plated for soldering. The terminations make true ohmic contact with the resistive layer along the entire side of the resistive element, thereby minimizing temperature variations. The resistor element is designed to uniformly dissipate power, thus minimizing parasitic contact resistance, and contact resistance variation for a low thermal EMF of 3 μV/°C.

Traditional passive current sensors and shunts generate heat under power, which changes their resistance, and thus their voltage output. The CSM’s low absolute TCR reduces errors due to temperature gradients, thus reducing a major source of uncertainty in current measurement. The CSM can withstand unconventional environmental conditions, including the extremely high temperatures and radiation-rich environments of down-hole oil exploration and well logging, or the deep-sea underwater repeaters in cross-ocean communications.

Featuring a four-terminal (Kelvin) design, load-life stability to ± 0.2% at 70°C for 2000 hours at rated power (typical current sensing resistors offer a load-life stability of ≥ 0.5% through a 1000-hour workload), and available with screening in accordance to EEE-INST002 (MIL-PRF 55342 and MIL-PRF 49465), the devices provide high stability and performance in precision current-sensing applications.