The present paper pinpoints the basic principle of probe-type electromagnetic flowmeters. On the basis of both electromagnetics and fluid mechanics, analytical solutions to the flow induced potential for different types of the meter, including circular cylinder probes with one or two pairs of electrodes, elliptical cylinder probe and streamlined cylinder probe, have been obtained. The effects of boundary layers of the flow past a circular cylinder probe and the limited flow field on the probe output are also dealt with. The theoretical solutions show a clear linear relationship between the flow induced potential produced on the probe electrodes and the approach velocity. Some methods to postpone or avoid the boundary layer separation happening on the surface of the probe are suggested. The experiments on circular and elliptical cylinder model probes substantiate the theoretical results.