Apparatuses and methods for analyzing particles using an impedance sensor. A flow-through impedance sensor may use two in-line electrodes driven in counter phase. A common sensor electrode may be used to, for example, detect impedance and determine trajectories through the sensor area. The sensor may be used in a wide variety of applications, including but not limited to use with microfluidic devices for determining particle characteristics such as position, velocity, size, and concentration as well as detection of bacterial spores and other biological agents of potential use in warfare and bio-terrorism.