Abstract: A cytometer includes a plurality of measurement sections, each comprising first and second sidewalls and a base therebetween, the sidewalls and base defining a channel portion extending from an entrance to an exit; an electrode group arranged on the opposite sides of the base and part way between the entrance and exit, the electrode group comprising an upstream electrode, a centre electrode and a downstream electrode in the way of a trajectory between the entrance and exit, and in respective order; the measurement sections being connected together to form at least one measurement channel comprising a plurality of the channel portions connected together in series; and, a lock-in amplifier; the central electrode of each group connected to the excitation signal port of the lock-in amplifier, and the upstream and downstream electrodes connected to the voltage differential input ports of the lock-in amplifier.