Electrical Resistance Tomography Linear Sensors. ERT sensors comprise of multiple electrodes which must make electrical contact with the fluid within the process volume. The most common geometry is a circular sensor with the electrodes arranged uniformly around the circumference. Electrical Capacitance Tomography Sensors ECT sensors comprise of multiple electrodes arranged around the circumference of a pipeline. The most common arrangement is for external electrodes mounted on a section of non-conducting pipe with an external earthed screen. The electrodes can be etched from flexible copper coated laminate. This arrangement has the advantage that the electrodes are non-invasive and non-intrusive. Dual Modality Sensors ITS have developed dual-modality ERT and ECT pipeline sensors with co-located electrodes for use with the m3000 system. These have internal ERT electrodes and external ECT electrodes.