MK21 Series

Magnetically operated Reed Sensor with mounting holes for screw fastening


MK21 sensors are magnetically operated Reed proximity switches designed for screw mounting. The sensor should be mounted on a fixed surface with the actuating magnet on the moving surface.  Introduction or removal of the magnetic field determines the closing and opening of the Reed Switch.  Leads are Teflon coated.   The magnetic pull-in / drop-out sensitivity is divided into four AT ranges.  A choice of switches, termination options and cable lengths is offered.


Position and limit switch, e.g. pneumatic or hydraulic actuator position indication and end travel limit switch

Door and window contacts, for security system applications

Level Sensor, use with magnetic floats for water level detection e.g. coffee-makers, washing-machines, dish-washers

Machine Industry


Tolerance +/- 0.10mm (0.004 inch)


The standard termination is a two-wire flat cable with a cross section of 2 x 0.14mm². The standard length of the cable is 500mm, other lengths can be supplied on request. The required length has to be noted on the part number. The cable end can be supplied with the following connection styles (please note after the length in the part number).

W Cable end cut, dismantled on 30 mm, cores stripped and tinned on 5 mm (0.2inch)


Contact Data

Contact type 71 84
Contact form A/dry A/dry
Rated Power max. (W) 10 10
Switching voltage max. (VDC) 1801 400
Switching current max. (A) 0.5 0.5
Carry current (A) 1.02 1.0
Contact resistance max. mOhm 150 150
Breakdown voltage (contact/contact) min. (VDC) 2103 700
Operating time incl. bounce (ms) 0.5 0.5
Releasing time (ms) 0.1 0.1
Operating temperature (°C) -20/+85 -20/+85
Storing temperature (°C) -35/+85 -35/+85

1Range D & E: 200 VDC 2Range D & E: 1.75 A 3Range D: 280 VDC; Range E: 310 VDC

Other switches by request.
Magnetic Sensitivity

Sensitivity class B C D E
Pull-in AT range 10-15 15-20 20-25 25-30
Available switches 71 71/84

This data relates to unmodified Reed Switches before mounting. Please refer to the respective single data sheets for sensitivity data and measurement methods for finished assemblies.

Order information

Ordering example

MK21 – 1A71 C – 500 W

MK4 Reed Sensor, 1 form A switch type 71, Sensitivity class C, Cable length 500mm, Termination W

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