A normally closed or Form B reed sensor represent the state of contacts before any magnetic field is applied to them in which they exist in the closed state. To open the contacts a magnet of opposite polarity is brought into the existing magnetic field cancelling the field from the existing permanent magnet. This in turn opens the contacts. The magnet must be carefully chosen so that its strength is strong enough to cancel the field from the permanent magnet, but not too strong that it overpowers the permanent magnets field, which could re-close the contacts. Furthermore, care must be taken in selecting the physical operate and release points.
Basic technical specifications*
| Reed Sensor Series |
Dimensions (mm) |
Contact Form |
Operating Range |
Rated Power Max. (W) |
| MK01 | 1B (N.C.) | 10 – 60 AT | 10 | |
| MK02 | 1B (N.C.) | 4,5 – 15 mm | 10 | |
| MK03 | ø5,8 x 25,5 | 1B (N.C.) | 10 – 60 AT | 10 |
| MK04 | 1B (N.C.) | 10 – 60 AT | 10 | |
| MK05 | 1B (N.C.) | 10 – 60 AT | 10 | |
| MK07 | M8 | 1B (N.C.) | 10 – 60 AT | 10 |
| MK08 | 1B (N.C.) | 10 – 60 AT | 60 | |
| MK11 (design: stainless steell) | M5; M8 | 1B (N.C.) | 10 – 60 AT | 10 |
| MK11 (design: brass) | M6; M8; M10; M12 | 1B (N.C.) | 10 – 60 AT | 100 |
| MK11 (design: plastic) | M8 | 1B (N.C.) | 10 – 60 AT | 100 |
| MK13 | 1B (N.C.) | 10 – 60 AT | 10 | |
| MK14 | 4 x 25,5 | 1B (N.C.) | 10 – 60 AT | 10 |
| MK15 | 1B (N.C.) | 10 – 60 AT | 10 | |
| MK21P, MK21M | 1B (N.C.) | 10 – 60 AT | 10 | |
| MK24 | 1B (N.C.) | 5 – 25 AT | 3 | |
| MK25 | 1B (N.C.) | – | 10 | |
| MK26 | 1B (N.C.) | 10 – 60 AT | 100 | |
| MK27 | 1B (N.C.) | 10 – 60 AT | 100 | |
| MK28 | 1B (N.C.) | – | 10 |
* Complete technical specifications can be found in the contact series data sheet
- N.O. – Normally Open
- N.C. – Normally Close