Abstract: Described herein are systems and methods for improving performance of single-frequency (single-point, single-bin) discrete Fourier transform (DFT) detectors by elimination of systematic errors from the detector output. Calibration procedures known in the art for practical implementations of such detectors do not provide adequate reduction of these systematic errors thus reducing utilization of these detectors in useful applications and products. The described methods, systems and devices allow such detectors to measure both DC and AC signals and, in latter case, considerably expand the operation frequency range without any additional hardware. These methods enable wide practical applications of DFT detectors across diverse variety of fields: from monitoring health of mechanical structures and fluid properties to impedimetric measurements in electrochemistry, monitoring of corrosion and bioimpedance.