Sensors 101 - Understanding Sensors within a fluid control system

07 August 2014

In the world of fluid control systems today, very little can be achieved without the raw data supplied by sensors, which need to be carefully specified to ensure that they are suited to their application. These sensors can help facilitate a variety of tasks from displaying process information and performing control functions to operating alarms, but each one has to communicate information to a process controller.

Kieran Bennett, of process control specialist Bürkert, looks at the range of sensors available, the different technologies used in their design and how the application affects the specification.

Flow sensors

In any production control system it is crucial to know the quantity of fluid that is actively involved in the process and this is where the flow sensor needs to be able to accurately indicate the flow. There are a number of different designs which have particular characteristics, making them better suited to a specific application or fluid medium.

Paddle wheel designs require direct contact with the fluid and are better suited to fluids with very low solids content, especially media with similar characteristics to water. The paddle wheel, which contains permanent magnets, is caused to rotate by the fluid flow and this movement is detected by a Hall sensor located outside the fluid area. The integrated electronics then convert this into a square wave frequency signal, which can be used by the process controller.

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