中圖分類號：TN98 文獻標志碼：A DOI: 10.16157/j.issn.0258-7998.245400
中文引用格式： 楊學文，陳靈強，馬凱元. 改進LCR儀表測量穩(wěn)定性的相位裕度優(yōu)化方法及硬件實現(xiàn)[J]. 電子技術(shù)應用，2024，50(12)：70-76.
英文引用格式： Yang Xuewen，Chen Lingqiang，Ma Kaiyuan. Phase margin optimization method and hardware realization to improve the measuring stability of LCR instrument[J]. Application of Electronic Technique，2024，50(12)：70-76.

Phase margin optimization method and hardware realization to improve the measuring stability of LCR instrument

Abstract： To address the self-excitation issue in the measurement of capacitive impedance using LCR meters, an LCR instrument has been developed to enhance measurement stability. By analyzing the phase margin of the self-balancing bridge circuit at the measurement front-end, a phase compensation circuit has been employed to resolve the self-excitation problem caused by phase lag. Utilizing direct digital frequency synthesis combined with a phase calibration circuit design, quadrature measurement signals of accurate phase are generated. A switch-phase discriminator lock-in amplifier is used to process weak signals, which are sampled by a 16-bit analog-to-digital converter and input into the microprocessor for vector signal synthesis and output display. Compared to professional instruments, the prototype designed has achieved a relative error of up to 0.5% for resistance measurements and up to 1% for large capacitance measurements.

Key words : self-balancing bridge；phase margin；direct digital frequency synthesis；phase-locked amplifier