Identification Systems - Introduction Mutual interference of the heads

Inductive read/write heads which are mounted in the immediate vicinity of each other can be subject to mutual interference. Certain safety distances must also be observed for inductive sensors using similar frequency bands. If the mounting is too close, the read/write distances may be significantly re-duced. Roughly 20 times the head diameter should be observed as the safety distance.The system IDENT Control offers the possibility to address the read/write heads one after the other. In this so-called Multiplex Mode, the heads can also be placed directly next to each other, at the expense of the reaction time.In the case of microwave systems, there is the additional possibility of over-ranges and reflections on metal. For these systems, a safety distance of at least 5 times the read distance (parallel adjustment) or 10 times the read distance (opposing adjustment) should be observed.

Number of read/write cycles

Inductive passive code carriers can be read as often as desired and thus have an almost unlimited lifetime. Data carriers on EEPROM basis can only be written to a certain number of times (typically 100000 times). If these da-ta carriers are operated at approximately 25°C and a data hold time of only one month is required, significantly more than 1 million write cycles can usu- ally be achieved.Inductive data carriers with RAM memory can be written to more quickly and have an integrated battery. In the case of these data carriers, the read/write cycles depend on the battery life (typically 6...8 years, 500000 write cy-cles).Microwave data carriers are active components containing a battery. They are also limited due to the battery life. However, the battery can be replaced and the data carrier can continue to be used.

Wiring and EMC directives

Signal cables are normally screened, but nevertheless they are especially sensitive to external electromagnetic fields. For this reason, no power-con-ducting lines such as the 230VAC supply, three-phase current or strong consumers such as engines should be laid in parallel.Furthermore, it must be ensured that the power supply including the distri-bution in the switch cabinet is positioned separately from the signal and bus cables.The earthing information on the devices and in the manuals must be ob-served. Both the read heads and the control units must be connected with earth potential on both sides.For further information, a manual on all relevant EMC topics is available un-der the order number #104880 or on our Internet page.
Issue date 2005-08-18 - Catalogue Identification Systems 2005/2006 Subject to reasonable modifications due to technical advances.Copyright Pepperl+Fuchs, Printed in German y Pepperl+Fuchs Group • Tel.: Germany +49 621 776-0 • USA +1 330 4253555 • Singapore +65 67799091 • Internet http://www.pepperl-fuchs.co m

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