Reed Switches - Introduction

I apologise for posting my entry very late on the blog. The reason behind this is my injury because of what I was on the bed for more than 4 weeks and I could not do any work. After four weeks, I did my work but could not post it on the blog because of no internet access.

Reed switches are tiny switches that contain magnetisable, flexible, metal reeds whose end parts are separated by small gap when the switch is open. When they are exposed to a magnetic field, the magnetisable metals inside the switch tend to come in contact with each other and hence completing the electrical circuit. Since these reeds are quite stiff, it causes them to separate, resulting in an open circuit. This happens when there is no magnetic field.

The most important quality of these types of switches is their sensitivity to magnetic field. Its sensitivity is measured in ampere-turns, corresponding to the current flowing through the coil to the number of turns. The sensitivity ranges between 10 to 60 Ampere-turns for commercial devices. The lower the value of AT is more sensitive the switch is.
In manufacturing, a metal reed is inserted in each end of a glass tube and the ends of the glass tube are sealed by heating. They are heated so that both ends seal a portion of the reed. The glass of the tube is infrared absorbing glass, has a high electrical resistance and must not contain volatile components such as lead oxides and fluorides.