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Secondary-Standard Devices Based on New-Generation Bulk Metal® Z-Foil Technology With Shelf-Life Stability of 2 ppm for at Least Six Years (Unaffected by Humidity)
MALVERN, PENNSYLVANIA — Nov. 22, 2010 — Vishay Precision Group, Inc. (NYSE: VPG) today announced that its Vishay Foil Resistors division has released a series of hermetically sealed metrology and laboratory grade ultra-high-precision Bulk Metal® Z-Foil resistors built on a new-generation Z-Foil technology that produces new benchmark capabilities for accuracy, stability, and speed. The VHZ devices feature a TCR of ±0.2ppm/°C typical from -55°C to +125°C, +25°C ref., and ±0.05ppm/°C from 0°C to +60°C, resistance tolerance to ±0.005% (to 0.001% is available), load life stability to ±0.005% (50 ppm) at 70°C for 10,000 hours at 0.15 W, and Power TCR (ΔR due to self heating) of ±5ppm at rated power of 0.6 W at +70°C and 0.3 W at +125°C.
The new hermetically sealed resistors released today offer an immediate answer to many resistor applications previously thought to be unsolvable, including secondary standards, feedback devices for operational amplifiers, precision voltage dividers, meter multipliers, precision bridge resistors, and decade voltage dividers. The VH102Z offers a resistance range from 10 Ω to 100 kΩ, while the VHZ555 resistor offers a resistance range of 4.99 Ω to 121 kΩ .The VHZ555 is manufactured on the same production line and is subjected to all the same process and lot control requirements imposed on the RNC90Z version, as well as all of the special screening, environmental conditioning, and documentation stipulations outlined in MIL-PRF 55182/9. Vishay Foil resistors are not restricted to standard values and specific “as required” values (e.g. 1.2345 kΩ vs. 1 kΩ) can be supplied at no extra cost or delivery time.
The devices’ hermetic sealing eliminates the ingress of both oxygen, which degrades resistors over long periods, and moisture which degrades resistors more quickly. Featuring a hermeticity of 10 ^-7 atmospheric cc/s maximum, the resistors offer a shelf life stability of 2 ppm total for at least six years. The devices are made with glass-to-metal seal enclosures employing Kovar eyelets which allow the copper leads to pass through the enclosure to minimize the thermal EMF from the lead junctions. Rubber fill between the metal housing and resistance element acts both as a mechanical damper and thermal transfer path.
The Bulk Metal precision Z-Foil resistor elements by VPG are virtually insensitive to destabilizing factors. Their element is a solid alloy that displays the desirable bulk properties of its parent material, and thus is inherently stable and noise-free. The alloy and matched substrate form a single entity with balanced temperature characteristics for an unusually low and predictable TCR. Resistance patterns are photoetched to permit trimming of resistance values to very tight tolerances.
The VH102Z and VHZ555 feature electrostatic discharge (ESD) immunity up to at least 25,000 V, a rise time of 1 ns, with effectively no ringing, a thermal stabilization time of <1 s (nominal value achieved within 10 ppm of steady state value), and current noise of <-40 dB. The devices offer a non-inductive (<0.08 μH), non-capacitive design, thermal EMF of 0.1 µV/°C maximum, a maximum working voltage of 300 V, a voltage coefficient of <0.1 ppm/V, and feature lead (Pb)-free or tin/lead alloy terminal finishes. For similar hermetically-sealed resistors with 0.001% tolerance, see model VHP100 or the VHA series.
The VHZ series was developed by the Vishay Foil Resistors Company as a new resistor concept, through the use of a proprietary Bulk Metal Z-Foil and new ultra-fine photo-etching techniques created by the company, so that the conductor can be considered a flat wire. Because the metals are not drawn, wound, or mistreated in any way during the manufacturing process, VHZ resistors maintain all of their design, physical, and electrical characteristics. The temperature coefficient of the resistor is carefully controlled through compensation techniques to eliminate the effect of different coefficients of expansions for all materials used in the resistor. With the VHZ devices, only a minimal shift in resistance value will occur during the device’s entire lifetime. Most of this shift takes place during the first few hundred hours of operation, and subsequent change is negligible.
While the hermetically-sealed series of Bulk Metal Foil resistors is already more stable than other resistor technologies and more stable than any other foil resistors, this stability can be further improved through a specially selected process of stability enhancements. These enhancements may be achieved through special post-manufacturing operations (PMO testing), including short time overload, accelerated load life, and temperature cycling.
Samples and production quantities of the VHZ series resistors are available now, with lead times of five days for samples, and eight weeks for standard orders.
About Vishay Foil Resistors
Vishay Foil Resistors is a division of Vishay Precision Group, producing the most precise and stable resistors available. Our portfolio comprises products in a variety of resistor configurations and packages to meet the needs of a wide range of applications: discrete resistors and resistor networks in surface mount and through-hole (leaded) configurations; customized chip resistor networks; precision trimming potentiometers; and discrete chips for use in hybrid circuits. Our foil resistors and current sensors are used in applications requiring a high degree of precision and stability, such as in medical testing equipment, high performance audio equipment, precision measuring instruments and aerospace and military applications.
About Vishay Precision Group
Vishay Precision Group produces sensors based on precision resistive foil technology, and sensor-based systems. We provide vertically integrated products and solutions for multiple growing markets in the areas of stress, force, weight, pressure and current measurements. As a spin-off from Vishay Intertechnology, our decades-long track record encompasses innovations in foil precision resistors, which we invented, current sensors, and strain gages, which have served as a foundation for our more recent expansion into strain gage instrumentation, load cells and transducers, weighing modules and complete systems for process control and on-board weighing. Vishay Precision Group may be found on the Internet at www.vishaypg.com