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 (R 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 target applications, such as 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. Vishay Foil resistors are not restricted to standard values, and specific ‘as required’ values (eg, 1,2345 kΩ vs. 1 kΩ) can be supplied at no extra cost or impact on 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 minimise 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 are virtually insensitive to destabilising 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 kV, a rise time of 1 ns, with effectively no ringing, a thermal stabilisation 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, and a voltage coefficient of <0,1 ppm/V, and they feature lead-free or tin/lead alloy terminal finishes.
For more information contact Marian Ledgerwood, Future Electronics, +27 (0)21 421 8292, [email protected], www.futureelectronics.com
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