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Power current-sensing resistors feature thermal stabilization of <1s

Tue, 07/16/2013 - 2:14pm

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Vishay Precision Group announced that its Vishay Foil Resistors brand (VFR) has released two new ultra-high-precision hermetically sealed Z-Foil power current sensing resistors with 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%. Designed to provide optimal performance when mounted on a chassis or cooled heat sink, the hermetically sealed VHP4Z and VPR247Z offer power ratings of 10 W (heat sink) and 3 W (free air), and a four-terminal Kelvin configuration for increased accuracy in high-power applications. 

The VHP4Z and VPR247Z offer a welded construction and a screw-mount for direct attachment to a metal heat sink. Hermetic sealing and a nitrogen back-fill for the VPR247Z provide maximum protection against environmental stresses to ensure long-term stability. 

Ideal for applications such as test and measurement where rapid ΔR stabilization and resistance stability under transient power conditions are required, the devices offer excellent load-life stability down to ±0.005% typical (50 ppm) at 3 W (heat sink) at +25°C for 2,000 hours. While the VHP4Z's copper leads provide low thermal EMF, the VPR247Z provides a significantly reduced size and weight and features gold-plated copper leads for higher stability. 

The VHP4Z and VPR247Z offer 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. 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 offer a non-inductive (<0.08 μH), non-capacitive design.

Samples and production quantities of the VHP4Z and VPR247Z are available now, with lead times of five working days for samples and eight weeks for larger orders. Pricing for U.S. delivery starts at $42.05. Further information about the VHP4Z and VPR247Z and other Vishay Foil Resistors products is available at www.vishayfoilresistors.com.

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