Electromagnetic flow sensor

An electromagnetic flow sensor for an electromagnetic flow meter (201) is disclosed. The sensor comprises a body (204) or frame, a flow passage (252) through the body or frame, a part of a magnetic circuit (248, 295) supported by the body or frame for applying a magnetic field across the flow passage, and at least first and second electrodes (298) supported by the body or frame, the at least first and second electrodes arranged to sense a voltage in response to a conductive fluid flowing through the flow passage. At least a portion of the body supporting the magnetic circuit part and the at least first and second electrodes is configured to be insertable into a flow tube (206) through a single aperture in the flow tube.