Ultra-precision Mini-MELF resistors, designed for stability and accuracy - 29 August 2001 - Electrocomp

Ultra-precision Mini-MELF resistors, designed for stability and accuracy
29 August 2001, Passive Components

BCcomponents achieved a world-first in the passive component industry when it introduced its range of ultra-precision thin-film Mini-MELF resistors targeted for use in high-accuracy, high-performance applications such as test and measurement equipment, process control instrumentation and aerospace electronics.

Available with tolerance values as low as ±0,02% and temperature coefficients as small as 5 ppm/K, UMA 0204 Mini-MELF resistors bring all the advantages of space-saving surface-mount components to applications where accuracy, stability and lifetime are important design parameters.

"Precision resistors are critical to the performance of a wide range of transducers and measurement circuits," said Joachim von der Ohe, Product Manager. "With the introduction of our ultra-precision UMA 0204 resistors, designers can replace existing metal-foil resistors with a smaller and lower-cost thin-film solution."

When determining the total error budget for precision resistors, their initial tolerance and temperature coefficient are only part of the story. Designers must also take into account the long-term drift in ohmic value due to ageing. This is particularly important in applications where a very long lifetime is required or where the component cannot easily be replaced, such as in space satellites, he says. It is also an important factor in the automotive electronics industry, where there is an increasing need to build modules that are capable of withstanding ever higher ambient temperatures, but at the same time are required to stay within pre-determined stability and precision requirements.

For a continuous power dissipation of 0,07 W, UMA 0204 resistors are guaranteed to drift no more than 1200 ppm (0,12%) during their minimum specified lifetime of 25 years. Even at their maximum rated power dissipation of 0,25 W, long term drift is guaranteed not to exceed 0,3%. The failure rate for UMA 0204 resistors is less than 0,7 x 10-9/h.

UMA 0204 resistors are available with initial tolerances of ±0,02, ±0,05, ±0,1 and ±0,25%, and temperature coefficients of 5, 10 and 15 ppm/K. The standard range includes all E192 values between 22 W and 221 kW, with other values available to special order.