Glossary / keyword index


AT-value (Ampere-turns)

is the English designation of the AW value. It defines the magnetic sensitivity of a reed switch. It is calculated from the number of turns of the magnetic coil times the current flow through the coil at which the reed contact switches.


Breakdown voltage

defines the voltage above which a breakdown occurs between the opened contact tongues of the reed switch.



of a reed switch is measured at the open contacts. The values are in the range of 0.1 … 1.0 pF. The low contact capacitance is a special feature of reed contacts.



Designates a structure with contact tongues that are necessary for the function of a reed switch or electromechanical relay. A contact always has at least two contact tongues, which can be symmetrical or asymmetrical in the glass body.

Contact bonding

is the situation in which the contact tongues are permanently welded together due to electrical overload of the reed switch. As a result, the switching function is no longer given, the contact has permanent continuity.

Contact form

Reed contacts and reed sensors have different contact types
(form A: normally open, form B: normally closed, form C: changeover).


Contact resistance

is the electrical resistance of a closed switch. It is measured after the contact has closed safely. The contact resistance of a reed switch is typically between 50 and 100 mOhm.



is the reduction of the magnetic force of a magnet. This is done by a counter field, temperature influence or radioactive radiation.

Drop-out value

indicates the voltage, current or flow value at which a reed switch or reed relay opens again. This is measured in V, A or AW.


Electrostatic shield

prevents crosstalk of signals between the coil and one or more contacts in a relay. The shield is usually made of copper and is led out at one or more points.


Holding voltage

is the voltage at a relay coil that is needed to keep a reed switch still closed.


Holding current

is the current through a relay coil needed to keep a reed switch still closed.

HG-wetted switches

are reed switches with a thin mercury film over the contact tongues. This achieves bounce-free switching, a high load capacity with a long service life and a low contact resistance that remains constant over the service life.

High insulated relays

have a very high insulation resistance of up to 100 TOhm. They are used, among other things, for switching voltages in the nanovolt range or for switching femto-amps.


of a reed switch is the difference between the response and dropout flux in a test coil. The hysteresis is often also given as the ratio of the drop-out value to the response value in %. The hysteresis depends on the construction of the reed switch. (contact tongue coating, coating thickness, contact tongue geometry).


IP protection classes

The IP codes define the degree of protection against the ingress of foreign bodies and water. This allows you to assess how suitable this product is for different environments.

Insulation voltage

is the voltage value that defines the insulation of an open contact, between two contacts, between contact and winding or between contact and shield or conductive housing.

Insulation resistance

is the DC resistance in ohms, measured at the open contact or, in the case of a relay, also between contact and winding or contact and shield. The measurement is usually carried out with 100 V/DC.



is a body surrounded by a permanent magnetic field. If it is brought close to a reed switch, the reed contact switches as a result of the magnetic flux (contactless switching).

Magnet pole

is located at the end of a magnet. This is where the field line density is greatest and where the magnetic force is also strongest (north and south poles of a magnet).

Magnetic shield

consists of ferromagnetic (magnetically conductive) material and is usually placed over the coil of a relay. This reinforces the magnetic flux within the winding and largely shields it from the outside. It contributes to the safe switching function and at the same time provides protection against external magnetic fields.

Magnetic sensitivity

Refers to the pick-up and drop-off point of a reed switch and is usually expressed in AW (AT).

Meltdown zone

is the area of the reed switch where the connecting wires or contact tongues are fused into the glass body.


Nominal voltage

is the defined, ideal voltage for the operation of a coil (a relay).


Operating temperature

determines the temperature range in which a reed switch, a reed sensor or a reed relay operates safely. Our specifications in the data sheets are for an ambient temperature of 20°C.


Reed relay

is a relay based on a reed contact as a switching element. Here, one or more reed contacts are located inside the coil. By applying the nominal voltage, the coil generates a magnetic field, which causes the reed contact to switch.

Reed sensor

is a reed contact encapsulated in a housing with connection leads or connection plugs. There are different housing shapes and different housing materials. Reed sensors are mostly used as position sensors.


is an electrical switching element with a control circuit and a load circuit. The control and load circuits are galvanically isolated from each other. An armature is actuated via a magnetic field generated by a coil, which opens or closes the contacts in the load circuit. Large voltages and currents can be switched with a small control voltage.

Reed switch

is a magnetically actuated switching contact. Here, 2 contact tongues are hermetically sealed in a glass tube with a protective gas filling.

Response time

is the time in ms from switching on the coil voltage to switching the reed contact.


is an abbreviation for “Restriction of (the use of certain) Hazardous Substances in electrical and electronic Equipment”. In German: Restriction of the use of certain hazardous substances in electrical and electronic equipment. The aim is to protect human health and the environment. These include, for example, lead in soldered connections, flame retardants in cable insulation, and many more.


Stainless steel

is a designation for unalloyed and alloyed steels with a special degree of purity. It is often used as a housing material for products that require special properties, e.g. high temperature resistance, high chemical resistance.


Switching current

is the current to be switched by the reed contact or reed sensor. This must not exceed the max. permissible value (not even for a short time).


Switching distance

is the distance in mm between the reed sensor and the actuating magnet at which a reed sensor switches.


Switching hysteresis

is the difference between the switch-on and switch-off point. It can refer to switching distances at the reed sensor or to response and drop-out values at the relay. It can be given in mm, V or as a ratio in %.


Switching voltage

The switching voltage is the maximum permissible voltage that a reed contact can safely switch. This voltage must not be exceeded, not even for a short time.