T: 0114 2015727
E: postmaster@sensdata.com

Sensdata Ltd
Unit B1
Sheffield Technology Parks
60 Shirland Lane
Attercliffe
Sheffield
S9 3SP
U.K.

Dr Robert E Brown - Pure Research Portfolio

• Electrical Impedance Tomography
• Disintegration and Arcing in Fuses
• Variance of the characteristics of physical distortions induced in cast metallic objects

Electrical Impedance Tomography
Electrical impedance Tomography, ‘EIT’ is a non-invasive imaging technique, where numerous electrical measurements are made around the periphery or boundary of a conductor to capture data representative of the conductor’s internal spatial impedance distribution. The aims of EIT are subsequently to reconstruct images, representative of conductivity. More often the data is analysed in the form of a system of linear equations to produce a sensitivity matrix or mapping matrix for a particular conductor. Subsequently, a back projection algorithm is used to recreate an image of conductivity.

This study was carried out with the objective to develop a system, which could determine to some degree the amount of solids in a liquid medium for example coal slurry.

Disintegration and Arcing in Fuses
A fuse is generally accepted to be the simplest form of protection device used to avoid damage to an electrical system by excess currents. This view stems from the simple construction of the wire type fuse and often leads to the assumption that the operation of a fuse is also simple. In general terms, the fuse is an electrical conductor, which melts when subjected to excessive current and due to disintegration subsequently interrupts current flow. The fuse is then irreparably damaged and can be viewed as being forfeited in the process of protecting the electrical system. Thomas Edison acknowledged this and described the role of the fuse as a ‘weak link’ in an electrical circuit.

Besides interrupting fault currents a fuse should conduct current for all conditions except those classed as faults. Furthermore after operation a fuse should present a high resistance to current flow. These attributes are fundamental to the role of the fuse but are commonly overlooked by all but the specialist.

More complex attributes of fuse operation, of interest to fuse designers and specialist users, are the requirements to avert potentially circuit-damaging disturbances generated during disintegration and furthermore to quickly force current interruption. These and other attributes are important in the role of semi-conductor and high breaking capacity current limiting fuses. Due to the diversity of fuse operating requirements, the range of fuse types is now vast.

This study was conducted with the intent to determine and rank the causation phenomena of fuse element disintegration with the object to devise irregular shaped fuse elements bonded to heat dissipating ceramic substrates which could be designed to amplify the principal causation phenomena to provoke much faster fuse operation.

Variance of the characteristics of physical distortions induced in cast metallic objects
A wine glass will "ring" when you "ping" it with your finger. The ring emanating from a cracked glass (or a glass partly full of liquid) will sound differently to a good and empty glass. This simple audible test is, in principal similar to the Vibration Analysis (VA) methodology used within this pure research project.

The VA technology used in this project was based on electronic instruments, which logically can now detect very subtle changes in the resonant frequencies of a sample as opposed to the human ear and thus further allows the extension of the normal frequency detection range to above 1MHz.

Vibration Analysis has been developed for industrial applications and is a whole-body resonance inspection technique that is particularly suited to inspecting smaller mass-produced hard components. One test will inspect the complete component without radiation, the need for scanning, and immersion in liquids, chemicals, abrasives or other consumables.

Hard components have their own resonant frequencies, for example a bell will ring with one specific note. This note is actually a combination of several pure tones, each representing a different resonance mode of the bell or harmonics of them. The tone of the "ringing" depends upon the size of the bell. This tells us that VA can differentiate between components of different sizes. A metallic bell and a glass bell of the same size will ring at different frequencies. This tells us that the resonant frequency is dependant upon the material of the tested component. In addition, a ‘sound’ good bell will ring true and resonate, whilst an abnormal ‘bad’ bell will ring dead and dampened. This tells us that we can detect cracks or porosity with Vibration

So what's new? People have been "inspecting" things by hitting them with a hammer and listening to them ringing for centuries. Computers and modern electronics technology have enabled us to take the human element out of the inspection process, thus measuring more frequencies and recognising more subtle changes than are detectable with the human ear. This also allows us to automate the process, eliminating operator error and further enables us to monitor higher frequency ranges to detect smaller differences.

This study was conducted with the intent to develop an instrument, which utilises precision impact and multi vibration sensor technology, neural, and statistical algorithm methodologies for the determination of sample soundness. Collectively, these attributes were shown to provide a rapid economical NDT system comparable with the attributes of more sophisticated systems and ideally suited for the yes/no decisions encountered in most casting processes.