为了对电磁发射系统中枢轨接触界面的接触阻抗进行测量与研究，研制了在低频条件下针对低阻抗的测量系统。通过阻抗变换法分别测量待测阻抗和标准阻抗两端的矢量电压，并通过基于自由轴的相敏检波法将矢量电压的实部和虚部分离开，根据标准阻抗电压和待测阻抗电压的相互关系求解待测阻抗的大小。系统通过STM32控制器作为信号发生器和控制器，采用开尔文四线法减小引线电阻和接触电阻的影响，采用软件补偿方法减小测量误差。测量结果表明，测量系统在10 kHz以内可正常工作，并且在测量100 Ω以内电阻具有较高精度。
In order to measure and study the contact impedance of the contact interface between the central rail and the electromagnetic launching system, a low impedance measurement system at low frequency is developed. The system measures the vector voltage at both ends of the impedance to be measured and the standard impedance separately by impedance transformation method. The real and imaginary parts of the vector voltage are separated by phase sensitive detection method based on free axis. The magnitude of the impedance to be measured is calculated according to the relationship between the standard impedance voltage and the impedance voltage to be measured. The system uses STM32 controller as signal generator and controller, adopts Kelvin four-wire method to reduce the influence of lead resistance and contact resistance, and uses software compensation method to reduce measurement error. The measurement results show that the measuring system can work normally within 10 kHz and has high accuracy in measuring resistance within 100 Ω.