Biased magnetic contacts on metal (cross posted)

Nov 07, 2004 2 Replies

Aritech DC103 biased magnetic surface contacts are being used on metal (ferrous) windows, they are secured using a chemical adhesive.



A number of them are not going into alarm when the window is opened, possibly due to the frame retaining some residual magnetism, would inserting an aluminium shim sandwiched between the frame and switch reduce this effect.



Any help or constructive advice would be welcomed.



Thanks in advance



Ian


On Sun, 7 Nov 2004 11:12:56 -0000 "Spider" used 15 lines of text to write in newsgroup: alt.engineering.electrical

Yes. You should shim the contact and the magnet to get them as far away from the ferrous metal as possible.

Sounds more like they're not installed correctly. One of the advantages of a BMS is that it is very difficult to dummy out the switch with an alternate magnetic source, if it is correctly installed. I would use a multimeter and ensure proper operation of the switch itself, the tamper, and that it is correctly wired. The chances of the metal in the window frame effecting its operation are...well not unheard of, but slim. I've used them on vault doors for over 20 years with no loss of magnetic power, and without any spacers. You may have a couple of bad switches...but I bet the magnet is not the issue.

Jack

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