Magnetic strip label of some of the questions
Q1: We all know we need better cobalt negative stress EM strips, but how to choose them?
A1: We could only distinguish the shape or thickness or brittleness of strips by eyes, we could not know their capability by our human eyes. We also could not distinguish the components or permeability or stress by our human eyes. We could only distinguish them by special equipments.
Q2: The EM strips are tested well when they are not set inside the book, but after being set inside the books, we find their sensitivity reduced when they are passing by the detecting channels, and there is a large blind area. Why do those things happen?
A2: You have bought iron strips or super microlite strips or low cobalt content strips set with gunwater. Since 2003, the price of materials has increased a lot all over the world and the price of cobalt has increased 200%~300%. Some factories changed the components of strips because they want to maintain the present price of EM strips. The content of cobalt should be more than 70% but they reduced it as less than 40%. So some users found that the capability went bad. Because users can not check the components of them, so they are easy to be cheated. What’s worse, some merchants sold the iron strips or super microlite strips or lower content cobalt strips to users as the price of well cobalt strips. This kind of selling is always with some temptations such as cash rebate. Users always believe them.
Q3: We bought the EM strips with stickers, but why is the sensitivity of some strips well, some bad?
A3: Generally speaking, most of the domestic strips with stickers are made of iron or super microlite. They can not be used without stickers. The alarm sensitivity of strips with stickers inside the books is not as bad as the strips with gumwater, but they are still worse than cobalt negative stress strips. And the stickers have time limitations which might be ignored by some users. Their time limitation is decided by their quality. Many library users have told us that their sticker strips inside the books dropt out from the books 2 years later when the stickers were dry.
Q4: Many library users said that the iron strips or super microlite strips are fragile, they are easy to be broken off by hands, but the cobalt strips are more difficult to be broken off. So could we distinguish the iron strips and cobalt ones by this?
A4: Iron strips and super microlite strips are fragile and they are easy to be broken off by hands, many of them present debris at the cutting place. The cobalt strips are tougher and they are more difficult to be broken off, even when they are broken, they won’t present debris. But this is not a scientific way to distinguish iron/super microlite strips and cobalt strips. Because some cobalt strips become fragile after heat treatment, and their quality is good.
Q5: I have seen a library worker paste the strips on detecting shelf, he said that we could distinguish cobalt strips and iron strips by only listening to the sound. Is this right?
A5: This is an old way used by many people. The material way is that: paste the strips (permanent strips will be better) that need checking on the detecting shelf (the outermost circuit will be better) under the open status of detectors, and then get close to the strips to hear, you could hear a sound of 2000HZ resonance with iron/super microlite strips but there is no sound with cobalt strips.
But the sound of 2000HZ resonance of iron/super microlite strips with stickers is not so obvious and this way cannot help you judge the components of strips and the permeability.
Q6: We don’t set burglarproof system before, but we are ready to set them. What kind of strips is better for us?
A6: It’s worth every penny of it. Cobalt negative stress composite strip is the best if the outlay is abundant or cobalt negative stress permanent strip is better if the outlay is tight. Both of the strips have good capability to protect books. Set one strip inside one book. Compare with sticker strip, they are hided very well. Bad quality products result in more cost for users. Because of the cost, better quality strips are more expensive which we have to accept. A book with one good quality strip is safe enough, but maybe you need to change the strips again and again with bad quality ones. So you could make your own wise choice