Magnetic Leakage Fields as Indicators of Eddy Current Testing
With eddy current testing in a homogenous field it is often spoken about hindrances that are represented by cracks to eddy currents that cannot flow so as in non-defective material. Such homogenous condition can be met with the magnetizing in a very long coil. If however the coil is short the field is not homogenous any more and especially with testing of ferromagnetic materials the magnetic leakage field may not be neglected. The demagnetizing effect of eddy currents can be seen also in magnetic leakage field. By proper arrangement of primary and secondary coil it is possible to get more information. It is given in the article how the longitudinal and the transverse cracks can be detected in the proposed arrangement of primary and secondary coils. If the arrangement of coils with the eddy currents testing is not a standard one it is very important to understand the physics of the new arrangement to be able to interpret the results properly. A very useful tool is the mathematical treatment of field equations. The numerical methods are often applied, since Maxwell equations are rather complex partial differential equations and there are usually real and imaginary components of the field to be taken into account. There are main ideas given how to solve more complicated problems. The actual concrete results will be compared with practical experiments.
Magnetic field around two separated magnetising coils
If the arrangement of coils with the eddy currents testing is not a standard one it is very important to understand the physical principles of the new one to be able to interpret the results properly. A very useful tool for this purpose is the mathematical treatment of field equations. The numerical methods are often applied, since Maxwell equations are rather complex partial differential equations and there are usually real and imaginary components of the field to be taken into account. In this article there are basic algorithms given that are used with the method of finite differences. There are only main ideas given as to how to solve more complicated problems. The actual concrete results are part of a broader project and will be published later.
Wireless temperature logging technology for the fishing industry
A system for autonomous temperature logging of fish catches is described. The system is completely wireless and is comprised of a number of loggers, in individual fish boxes, and a base station, assigned to a particular trawler. The temperature of the fish is monitored by the loggers, which contain a thermistor and RF transmitter circuitry. The data is sent at fixed intervals (usually 5 minutes) to the base station. Through a GSM modem, the base station communicates the collected data to the shore where a server uploads the temperature-time information to a database. The database and controlling software are completely Web-based and can be accessed by an Internet-enabled PC, laptop or PDA. This allows remote initiation and control of the system, in addition to querying of the database. To date, successful trials have been conducted for salmon, mackerel and whelk fishing off the Irish coast.