Vishay Precision Group, Inc. (NYSE: VPG) today announced that its Vishay Foil Resistors brand (VFR) has released new ultra-high-precision Z-Foil power current sensing resistors for applications where rapid ΔR stabilization and resistance stability under transient power conditions are required. Designed to provide optimal performance when mounted on a chassis or cooled heat sink, the VCS331Z, VCS332Z, VFP4Z, and CSNG Series feature low TCR of ±0.2 ppm/°C from -55°C to +125°C, +25°C ref., PCR (ΔR due to self-heating) of 4 ppm/W typical, and tolerances to ±0.01%. For high-power applications, the devices offer power ratings up to 10 W (on heatsink) and a four-terminal Kelvin configuration in order to remove the unwanted influence of lead resistance and lead sensitivity to temperature.
The VCS331Z, VCS332Z, VFP4Z, and CSNG offer excellent load-life stability to ±0.005% typical (50 ppm) at 3 W (heat sink) and +25°C for 2,000 hours, a thermal stabilization time of <1 s (within 10 ppm of steady state value), and a wide resistance range from 0.25 Ω to 500 Ω. (Lower and higher values are also available.) Any resistance value within this range is available at any tolerance with no additional cost or lead time effect. The resistors offer a rise time of 1.0 ns with effectively no ringing, current noise of 0.010 µVrms/V of applied voltage (<-40 dB), and a voltage coefficient of <0.1 ppm/V. The devices withstand ESD to at least 25 kV for increased reliability, and they offer a non-inductive (<0.08 μH), non-capacitive design.
“In applications such as force-balance scales, electronic beam deflection systems, and switching power supplies, accuracy and repeatability are likely to be more important than power handling requirements and depend to a major extent on precision current sense resistors with Kelvin connections,” said Yuval Hernik, Senior Director of Application Engineering for VFR. “The resistors must have extreme thermal efficiency, well-distributed internal heat from power dissipation, very low thermal EMF, and fast thermal stabilization. All these characteristics, which can be found in the VCS331Z, VCS332Z, VFP4Z, and CSNG, are necessary to prevent errors caused by uneven heat from external sources such as the power amplifiers and other circuit elements.”