A Method for Measuring Ultra Low Frequency Alternating Current

Measurements of small AC currents below $10 \mathrm{~Hz}$, or even $1 \mathrm{~Hz}$, are required for on-orbit performance prediction of spacecraft batteries, $1 / \mathrm{f}$ noise testing of operational amplifiers in space environments, and neurostimulation conduction tests in biology. According to the data published in the Key Comparison Database (KCDB) on the International Bureau of Weights and Measures (BIPM) website, AC current measurements can only be calibrated above $10 \mathrm{~Hz}$, the Ultra-Low-Frequency (ULF) current whose frequency is lower than $10 \mathrm{~Hz}$ can’t be tranced. This paper introduces an ULF AC current measurement system consisting of a current-to-voltage conversion (IVC) device, an ULF voltmeter and a microprocessor, which can realize the accurate measurement of AC currents in the range of $\mathrm{DC} \sim 10 \mathrm{~Hz}$, and it has been verified that the accuracy of measurement in the range of $1 \mathrm{~mA} \sim 100 \mathrm{~mA}$ can reach $1 \%$, which can provide a technological guarantee for the performance and safety of the spacecraft storage batteries.