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MALVERN, Pa. — June 17, 2013 — 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 2000 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 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.”
Many instrumentation circuits depend upon current sense resistors for precision measurements and system controls. The new devices can also be used in lithium-ion battery circuits for alternative energy applications where energy that cannot be harvested must be stored. In state-of-the-art battery management circuits, Bulk Metal Foil resistors can be used in the measurement of the “state-of-charge” (SOC) of the battery cells. The characteristics of Li-ion cells complicate SOC measurement, so precise ICs and precision current sense resistors with improved stability and low thermal EMF help to extend battery lifetime.
The Bulk Metal® Foil resistor is based on the planar construction of a cold-rolled Ni-Cr foil bonded to a flat ceramic substrate. The monolithic foil, as opposed to the agglomeration of particles in thin film resistors, has a strength and substance independent of the substrate, which gives the metal foil its own specific thermal linear coefficient of expansion (LCE). The foil also has a known and repeatable independent positive temperature coefficient of resistance (TCR). When the foil is bonded to the substrate, it attempts to respond to temperature changes in accordance with its own LCE, but is constrained to follow the lower LCE of the ceramic substrate. The resistance change due to the differential LCEs counter-balances the metal’s positive TCR for a near-zero net TCR of the resistor. The composite formation with a planar foil structure makes it possible to very accurately etch a pattern into the resistor that is non-inductive and non-capacitive, with low noise and low thermal EMF.
The VCS331Z, VCS332Z, and VFP4Z are differentiated by power rating, thermal EMF and configuration. The CSNG is a custom version of these resistors that can be uniquely designed and tailor-made to the customer’s specific applications and which has already been used by several research institutes and test and measurement companies
Samples and production quantities of the VCS331Z, VCS332Z, VFP4Z, and CSNG are available now, with lead times of five working days for samples and six weeks for larger orders.
Further information about the VCS331Z, VCS332Z, VFP4Z, CSNG, and other Vishay Foil Resistors products is available at www.vishayfoilresistors.com
About Vishay Precision Group
Vishay Precision Group (VPG) is an internationally recognized designer, manufacturer and marketer of: components based on its resistive foil technology; sensors; and sensor-based systems specializing in the growing markets of stress, force, weight, pressure, and current measurements. VPG is a market leader of Foil Technology Products, providing ongoing technology innovations in precision foil resistors and foil strain gages, which are the foundation of the Company’s Force Sensors Products and its Weighing and Control Systems. The product portfolio consists of a variety of well-established brand names recognized for precision and quality in the marketplace. To learn more, visit VPG at www.vishaypg.com.
About VPG Foil Resistors
VPG Foil Resistors, a part of Vishay Precision Group (VPG), produces the most precise and stable resistors available. Distinguished by the premier brands Vishay Foil Resistors, Powertron, and Alpha Electronics, the VPG Foil Resistors portfolio includes discrete resistors and resistor networks in surface mount and through-hole (fixed-lead) configurations; customized chip resistor networks; precision trimming potentiometers; and discrete chips for use in hybrid circuits. These devices are used in applications requiring a high degree of precision and stability, such as in medical testing equipment, semiconductor equipment, precision measuring instruments, aerospace, and military applications. To learn more, visit www.vishayfoilresistors.com.
Bulk Metal is a registered trademark of Vishay Precision Group, Inc.