The capability parameters of EM strips
1. Sensitivity
The special EM strips should alarm everywhere inside the detecting area even in the weakest field, which means the EM strips have enough sensitivity.
The sensitivity of strips is decided by the material. The sensitivity is decided by original permeability ¦Ì0 and maximum permeability ¦Ìm in magnetics. Higher ¦Ì0 and ¦Ìm mean the higher sensitivity. Higher sensitivity EM strip has 60%~70% corporation of cobalt. When the cobalt corporation is higher than 70%, ¦Ì0 and ¦Ìm will go smaller and the magnetization will reduce and the sensitivity of burglarproof strips will reduce contrarily.
2. Reliability
EM strips used in libraries need to be high reliable. The strips are set inside the books, but it will never influence the burglarproof capability. They are fixed by gumwater or latex generally, which result in strong stress on strips.
When EM strips are being magnetized when entering detecting areas, magnetostriction phenomenon happens on strips in magnetics. (The phenomenon that, when EM strips being magnetized, the length of the object will be elongated or shortened with the magnetized direction, is called magnetostriction. ) One magnetizing capability of the magnetizing material is magnetostrictive saturation factor ¦Ës, which is used to show the magnetostrictive extent of object length along with magnetizing direction in magnetization, higher ¦Ës means higher elongation or shortening.
? Set the iron EM strips inside the books and fix them with gumwater or latex or stickers. Magnetostriction phenomenon results in a big stress on strips in magnetostriction which will reduce the capability of strips even invalidate them totally.
? The ¦Ës of iron strips is about 10~35 (x10~6), outside stress has a huge influence on them. Their reliability is bad.
? The ¦Ës of cobalt EM strips is always lower than 5 (x10~6), outside stress has a smaller influence on them. Their reliability is better.