What is Process Tomography?
Tomography involves taking measurements around the periphery of an object (eg process vessel or patient) to determine what is going on inside.
The best known technique is CAT scanning in medicine, however process tomography instrumentation is cheaper, faster and more robust.
ITS provides electrical tomography instrumentation, software, sensors and technical support. This enables customers to continuously scan a volume and determine the distribution of electrical properties as they change over time.
Measurement principles
Process tomography operates by taking data from an array of electrodes in contact with the process media. These are either mounted on a baffle / dip-pipe or around the circumference of the pipe or vessel.
For a standard 16-electrode sensor, 104 voltage measurements are taken every 20 milliseconds using an AC current and 4-electrode measurement technique. The images show the electrical field lines spreading out into the vessel from a single measurement. They are affected by the presence of conducting (red) and non-conducting (blue) regions.
From measurements to data
A reconstruction algorithm converts the peripheral measurements to vessel conditions. This is an "ill-posed" problem and there are many techniques of addressing it. ITS offers two techniques, one for on-line operation, and another (more accurate) which requires post-processing.
From data to process information
Typically, tomography data is presented as a colour coded image: red for conducting to blue for non-conducting. However each image (tomogram) is composed of an array of derived conductivity measurements.
Data can be analysed statistically (e.g. variance to determine extent of homogeneity or average to give representative data through a volume) and dynamically (e.g. to determine rate of change of a feature).
