Sendyne’s New SFP101 Precisely Measures Current Using Shunt of Any Resistance Made of Any Material
Achieves ±0.05% Accuracy from -40°C to +125°C When Coupled to a 25 micro-Ohm Shunt, Handling Continuous Currents of 300A and Peak Currents of 2000A

New York, New York, October 16, 2014 –   A robust battery management system requires precise current measurements / Coulomb counting in order to derive State of Charge (SOC) and other important battery state information. While specialized high accuracy shunt-based current measurement systems are used by such entities as NIST, to date, commercial shunt measurement systems are limited in their accuracy by two main factors. The first is that the accuracy of even precision shunts is affected by changes in temperature caused either by the environment or by the self-heating of the shunt when high currents are flowing. The second is that historically, due to limitations imposed by offset error and noise, lower resistance shunts could not be used to meter small currents. Instead, a high-resistance shunt must be used; such shunts dissipate considerable heat and must be physically large, making them unsuitable for many applications.

Evolved from Sendyne’s award-winning SFP100 (EDN Hot 100 Products of 2013, UBM ACE Award Finalist: Ultimate Products - Analog ICs), Sendyne’s new SFP101 current, voltage and temperature measurement IC and board address these issues. The Sendyne SPF101 achieves a maximum voltage offset error of less than ±150 nanovolts (±0.15μV) for the measurements of the voltage drop across a shunt. Further, the SFP101 provides user-definable automatic compensation for resistance dependence of the shunt on temperature from –40°C to +125°C, and is programmable to accommodate shunts with an output voltage from ±10mV to ±300mV. This means that the SFP101 can work with a shunt of essentially any resistance made from any material.

For example, a copper busbar can have as large as a 35% error over temperature, making it unsuitable for use in exact current measurement. Due to the proprietary temperature compensation feature of the SFP101, that error is typically reduced to ±0.1%. Using a 25 micro-Ohm or 100 micro-Ohm shunt, the SFP101 typically achieves ±0.05% accuracy of current measurements. A 25 micro-Ohm shunt, such as those produced by Vishay, can now be used for high power applications, handling continuous currents of 300A and peak currents of 2000A while resolving currents as small as 250µA.

These specifications are not derived from theoretical calculations: they represent the actual performance of the entire measurement system, including thermocouple errors in the connections and EMI filter, verified through extensive lab testing with several types of shunts.

In addition, the SFP101 provides on-board calibration for both current and voltage, storing calibration values and applying them internally, offers separate charge, discharge, and total Coulomb counters and measures multiple temperature points to ±1°C.

“Sendyne is committed to bringing to market technologies that reduce the cost and improve the safety and efficiency of large battery systems, such as those used in electric vehicles and grid storage,” said Ellen Gooch, Sendyne’s Director of Marketing.


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