The key difference between ECT and ERT sensors is that ERT electrodes are in direct contact with the process whereas ECT electrodes are insulated through a thin non-conducting liner.
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.
The circular sensors are suitable for most pipelines and generally used for monitoring the flow of oil / gas systems or pneumatic conveying of powders, grain or plastics.
The pipeline material sections can be made of a variety of plastics:
Unless there are specific constraints, electrodes are made from copper.
ITS have also developed polymer lined stainless steel pipeline ECT sensors for more demanding conditions which can be provided with materials certificates when required. The electrodes are contained within a resin filled cavity between the polymer pipe liner and the external stainless steel pipe. The external stainless steel pipe ensures the pressure integrity and operating pressures up to 120 bar have been provided for certain applications.
For hazardous installations, ATEX rated sensors (to Ex mb IIC T4 or T3 Gb) have been supplied.