A method and apparatus for measuring the rate of flow of an ion-containing fluid in a channel are disclosed herein. The apparatus includes a captive sensor operable to detect changes in capacitance value due to the deflection of the ions in the fluid by a magnetic field, and a processor operable to determine a flow speed of fluid from the detected change in capacitance value and a predetermined value of magnetic field strength. Such apparatus may be implemented using CMOS technology. The apparatus may operate in a magnetic field generated by a permanent magnet and measure the flow reliably.