An inductive system for measuring microampere currents

This paper describes an inductive current measurement system (ICMS) which has been developed and used for measuring currents down to the μA scale. The need for such a measurement system came from an experimental setup developed with the purpose of determining the performance of a P2110 radio frequency energy harvesting board in terms of output power. The main components of the ICMS are two LTS 15-NP Hall effect current transducers. The measured signal is driven through one the transducers while the other transducer is used as reference. Both outputs are filtered and fed into an AD8230 rail-to-rail precision instrumentation amplifier (INA). The output of the INA is low pass filtered and fed into a National Instruments (NI) USB 6251 data acquisition system (DAQ). The DAQ is driven by a NI LabVIEW 2009 interface which performs system calibration based on a compensation table that contains the transducer output volt-current analogy and also performs current measurement. The entire system is battery powered and enclosed in a brass casing to reduce external magnetic interferences.