Low cost electrical current sensors with automatic measurement range

Abstract

We present a simple and low cost Smart Current Sensor with wide automatic measurement range. The logic core system of the sensor is the Atmel AT32UC3C2256C AVR 32-bit microcontroller, the wireless core is a Microchip MRF24J40MA IEEE 802.15.4 RF transceiver[3]. The MCU features 11 ADC multiplexed channels, with 12-bit resolution and sample rate up to 2Msps, two of which can be sampled in parallel. The sensing board consists of two hall-effect based current sensors, assembled on different PCBs in order to perform with different sensitivities. Custom primary conductor design allowed us to sense the current flowing in the conductor with two different sensitivities: the sensor mounted inside the two PCBs gets a strong contribution from the traces on both the PCBs, the sensor mounted outside only gets a strong contribution from the traces on the bottom PCB.