Design of digital sampling impedance bridge for battery impedance spectroscopy

The paper describes the design of a digital sampling impedance bridge dedicated for battery impedance spectroscopy, which has been presented at the 24^th IMEKO TC4 International Symposium and has been published afterwards as an extended, peer reviewed paper by IMEKO. It suggests topologies capable of measurement of sub-milliohm impedances in full complex plane. The paper also shows measurement uncertainty contributions of the digitizer nonlinearity and coaxial network of the bridge including parasitic inductive and capacitive couplings in the network. Combined uncertainty of the bridge with common NI 9238 digitizer ranges from less than 20 μW/W to order of 0.01% for voltage drop above 1mV at the measured standard in a frequency range 0.01 Hz to 5 kHz. Angular errors can be as low as 1 μrad for frequencies below 1 kHz when measured voltage drops exceed 10mV. The paper also presents experimental measurements showing capability to measure low impedances from 0.01 Hz to 5 kHz.