Battery Board Measures Current Without Shunt Resistor

Battery Board Measures Current Without Shunt Resistor

AMS’s latest reference design board measures current to an accuracy of ±1% by monitoring the voltage drop across a copper track on a printed-circuit board (PCB). The new technique uses AMS’s AS8510 data-acquisition front end, which features high sensitivity and precision with two measurement channels.

One channel is used to measure current by sensing the voltage drop over a 10-mm section of a PCB track with a known resistance value and temperature coefficient. The other matched channel measures the temperature of the copper track. This temperature measurement can be performed either internally by the AS8510 or by an external temperature sensor.

By applying a compensation algorithm developed by AMS, the AS8510 can eliminate the effect of the variation in the resistance of the copper track over temperature. This means that it can produce current measurements accurate to ±1% over its entire operating temperature range (–40°C to 125°C) without the normal requirement for a precision shunt resistor with a low temperature coefficient.

The new reference design is intended for small electric vehicles such as e-bikes and electric scooters. It can be used in applications drawing up to 40 A, but the design can be adapted to measure up to 100 A.

AMS

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