Reed switches, the basic parameters, control methods and scope

This is the second part of the article about the reed, which we will talk about the main parameters of the reed switch, the strengths and weaknesses of the product and on where they are used today.

The main parameters of the reed switch

In reed switches have a number of important electrical and mechanical characteristics, about which we will now discuss.

mechanical specifications

1. Magnetomotive force response. This characteristic tells us that, when a magnitude of the external magnetic field will circuiting or releasing the contact group. In those. documentation, these parameters are written as follows: V cp - magnetomotive force response, V TNA - magnetomotive force is released.

2. Operate and release time. It is the second most important parameter of all the reed switches, which shows how bystrodeystvenen a particular reed switch. The time is measured in milliseconds and is recorded in the documentation as: tcp, totp. In this case, the following pattern is observed: the smaller the size of the reed switch, the faster it works.

3. The maximum number of positives. This parameter tells, for a number of switching actions intended product.

electrical parameters

In this respect, the reed switches do not differ much from the most casual contact, that is, they have the same set of electrical characteristics, namely:

1. Transient contact resistance Rk. This value shows how the resistance has a reed switch when its contacts are closed.

2. insulation resistance Riso. A reed switch is a contact resistance in the open position.

3. Dielectric strength Ubr. This value indicates the breakdown voltage because of it is determined by the insulation quality of the reed switch, which shows how qualitative a vacuum or an inert gas is used for sealing internal area. As the magnitude of this voltage depends on a distance between the contact group in the reed switch.

4. Power Pmax. This parameter is determined by the material, size of the contact group, the method of treatment of the contact pads.

5. Capacity ck. This parameter is measured at open contacts and depends on the dimensions and spacing between the contacts.

Variants of reed switches control

Reed switches can be divided into a few groups:

- Management of permanent magnets.

- Management of the electromagnetic coil.

permanent magnet Control

This is the most common and simple control option when the magnet is moved relative to the reed switch in a linear fashion. A striking example of such an application is the simplest system, where a magnet is mounted in the door, and a reed switch mounted in the doorway is energized position with the door closed.

Other options for moving and placing the reed switches are used very rarely.

electromagnetic coil Management

This version is most common in applications of reed relays. These relays are arranged quite simply:

In the inner region of the coil current is mounted reed switch, it does not need to use all kinds of springs and levers (as in the classical relay). The only drawback of these relays is considered to be a small number of pins.

Such current Reed relays are widely used as an overload sensor system.

Pros and cons of the reed switch

In this world nothing is perfect, so that of the reed switch has pluses and minuses

pros reed switches

1. Increased reliability. Reed relays are very reliable and simple products and if they are compared with a simple contact group, then they (the reed) will be 100 times more reliable. Due to the increased strength and electrical insulation.

2. Performance. The switching frequency may be up to 1000 Hz, and the time of opening and closing the contacts 2 ms - 0.5 ms.

3. The number of operations may reach 5 billion times that are significantly higher than conventional contacts.

4. A simple way to match the load.

cons reed switches

Of course, the drawbacks are not so much, but still there:

1. Mostly switched load.

2. Number of contact groups in one flask was very small.

3. If you use a "dry" reed switch, it is necessary to take account of such features as contact bounce.

4. The glass bulb is very fragile and can not withstand mechanical stress.

That's all I wanted to tell you about the reed switch. If you liked this article, you will appreciate her huskies and thank you for your attention!