Bourns and Stackpole deliver current sense resistors for high-current sensing

By Jean-Jacques DeLisle, contributing writer

Developers
at Bourns Inc. have developed a new family of sense resistors, the CSM2F series,
which uses a metal alloy element that has been electron-beam-welded to
tin-copper terminals. This design is said to offer excellent electrical
properties, additional mechanical strength, and ease of solderability. An added
benefit of the metal-alloy current sense resistors is that it allows for a
minimal thermal electromagnetic field (EMF) as low as 0.25 µV/K.

The
CSM2F sense resistors are designed for use in high-current applications while
still providing very low resistance. The devices deliver resistance values as
low as 50 µΩ, continuous current of up to 1,000 A, and power ratings of up to 50
W. Engineered for design flexibility, the series features three different
footprint sizes: 8518, 7036, and 6918 metric.

The
high-current sense resistors also provide a low temperature coefficient of resistance
(TCR) of 50 ppm/°C at temperatures between 20°C to 60°C. This extremely low TCR
allows these sense resistors to maintain a desirably low drift of resistance
with temperature.

Three
different models comprise the new CSM2F series of resistors, all of which
feature metal-alloy construction and are RoHS- and AEC-Q200-compliant. These
model series include the CSM2F-8518 SeriesCSM2F-7036 Series, and
the CSM2F-6918 Series.

Thanks
to high measurement accuracy and “relatively” low cost compared to other
technologies, said Bourns, the current sense resistors are finding homes in
most market segments, particularly battery management systems in automotive,
industrial, and computer electronics.

Other
companies also have been developing new current sense resistors. Stackpole Electronics Inc. recently
launched the HCSM2818 5-W
surface-mount current sense resistor
. This new component features an
all-metal element as well as a molded construction in resistance values of 4,
5, 10, 15, and 20 mΩ. Along with an array of resistance values, tolerances of
1% or 5% are available. The device offers a TCR of 200 ppm for resistors below
10 mΩ and 75 ppm for values of 10 mΩ and higher.

The
new current sense resistors provide full-power operation up to 100°C and have an
operating temperature limit of 170°C, making them suited for high-power current
sensing that experiences significant self-healing, said the company. This
series also features large terminals that allow for a thermally efficient
connection, which helps reduce convection and conduction cooling, making them
suited for high-voltage applications.

The HCSM2818 series is RoHS-compliant and
halogen- and lead-free. The resistor series is priced at $0.38 each in full-reel
quantities. The parts are available direct or through Stackpole’s franchised
distributors.