The modified multi-features impulse track circuit is dedicated to solving shunt-fault problems confronted by traditional track circuit installed in station. Rail is a primary component of this track circuit. Analyses of rail impedance characteristics under continuous different frequency signals are meaningful for electric characteristic analysis and optimal design of this track circuit. However, the existing measurement systems for impedance characteristics can be only applicable to single-point frequency case. In the framework of Lab VIEW, this paper develops a new system with professional soundcard for achieving impedance measurement of rail or other metal conductors under sweep frequency signals. It can be...