US-based Vishay Precision Group Inc has announced that its Vishay Foil Resistors (VFR) division has introduced a breakthrough secondary standard resistor for laboratory calibration standards and digital multimeters (DMM). For test equipment designers, the new secondary standard foil resistor (FSR) offers exceptionally high accuracy of 10 ppm at the terminals, long-term stability of 0.0005 per cent (5 ppm) at +25 degrees C for one year, temperature coefficient of resistance (tcr) to 0.3 ppm/degrees C from +15 degrees C to +45 degrees C (max tcr:10 ppm to 30 ppm total deviation over temperature range), and resistance tolerance to 0.005 per cent (50 ppm).

Resistor based on new design
Offering a direct plug-in device for most DMMs, the FSR is based on a new design utilising its registered Bulk Metal Foil technology, resulting in a combination of standard features with new benchmark capabilities for accuracy, stability, and speed. By using VFR precision resistors instead of the inductive resistors featured in most secondary standard boxes, the FSR allows for controllable accuracy at the box terminals through calibration, while extending the frequency range by up to 10 times.

The device released is intended for adjustable, direct reading resistance and serves as a substitution component for RTD, bridges, attenuators, voltage dividers, multipliers, adjustable feedback resistors for use with operational amplifiers, and network ladder elements. In addition, the FSR greatly extends the usefulness range for these instruments due to its high-frequency performance, making them ideal for use in inspection stations, in the standards laboratory, and for component evaluation.

“Virtually all available conventional and specialised secondary standard resistors present a number of problems, including instrument accuracy; resistance shifts caused by load, temperature, or environmental changes; difficulty in measurement of the last digits; limitations on usable frequency; size; and ease of setting,” said Yuval Hernik, senior director of application engineering for Vishay Foil Resistors. “After an intensive analysis of these issues, we have developed a completely new design. With the unequalled combination of the Bulk Metal Foil resistors’ performance parameters, the FSR offers a level of accuracy, stability, and versatility never before combined in one secondary standard resistor, eliminating or reducing these problems to insignificance.”