A circuit breaker system 10 (FIG. 1) using electronic trip units 35 is disclosed. The electronic trip units 35 are coupled to a communications bus 30 whereby the electronic trip units 35 can be reconfigured, controlled, and/or monitored by a central computer. Further, the electronic trip units 30 include a data acquisition circuit 100 (FIG. 4) that uses chopping to provide better accuracy and increased dynamic range of current measurements.