Vishay Precision Group, Inc. (NYSE: VPG) today 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 to 500 ohms. 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.