Technical information

Our products are almost all RoHS and REACH compliant. There are few exceptions, such as mercury relays or some special sensors.

The correct selection of the housing material is important for the durable of the product. The selected material have to permanently protect the components (reed switch) inside the sensor in order to ensure proper functioning.

 

Selection criteria:

  • Minimum and maximum surrounding temperature
  • Medium in which the sensor is used
  • Maximum pressure in the medium
  • Mechanical stress

 

Possible housing materials:

  • Metal: stainless steel, brass
  • Plastic: PA, PC, PP, POM, others on demand

 

We will be happy to advise you on the selection of your optimal housing material for your application.

The Reed technic allows a non-contact switching of an electrical signal or voltage. Here, a defined external magnetic field acts on a special ferromagnetic switching contact, also called Reed switch . This magnetic field is usually generated by a permanent magnet or a coil.

 

Advantages of the reed technic:

  • Non-contact, low-wear switching process
  • Long service life
  • High switching frequency
  • Cost-effective alternative to electronic switch

 

General technical data

Switching distance
The switching distance is the distance at which the magnetic switch is actuated by approximation of the magnet. The length of the switching distance depends on the field strength of the magnet and the sensitivity of the reed contact.
Switching hysteresis
The switching hysteresis is the differential distance between the switching on and off points. It is mainly dependent on the type of reed contact. Switching point accuracy
A very high repetition accuracy of the switching point is given for magnetic switches. It is located in the range of approx. 0.02 mm with constant ambient conditions.response time (incl. bounce)
The response time depends on the Reedkontaktgröße in the range between 0.6 and 3 Ms. Relapse Time
The relapse time depends on the Reedkontaktgröße in the range between 0.05 and 2ms. Switching Speed
For magnetic switches with Reedkontakten up to 300 Hz, depending on the type and size of the reed contact. For switches with Hall element up to 100 khz, depending on the version. vibration resistance
The mechanical vibration resistance is in the range from 10 to max. 30 G. With magnetic switches with built-in spring set contact, the vibration resistance is lower, magnetic sensors with hall element are largely insensitive to mechanical shocks. protection type
All switches except float switches: IP 67, contact protection against dust ingress, water protection against immersion
Float switch: IP 68, contact protection against dust ingress, water protection against immersion

Switching Capacity-Example
The max. switching power is the product of switching current and switching voltage. In the case of alternating current variables, the current and voltage must also be multiplied by the power factor cos φ. However, the individual limit values must not be exceeded. The working area of the switch can be seen from the switching power hyperbolic.
Max. switching capacity of the switch = 30 Va. In the case of 24 V DC voltage, the following switching current must be observed:
IMAX = 30 VA: 24 v = 1.25 A.

Temperature range
-5 °c… + 60 °c (standard) extended temperature range on request-40 °c… + 150 °

Construction of the reed switchThe reed switch consists of 2 ferromagnetic tongues, which are hermetically sealed in a glass tube. These 2 switches overlap minimally and have a distance of only a few micrometers. When a magnetic field approaches the switches, they attract each other and then close the contact. If the magnetic field is weakened again (by removing the magnet), the contact opens again.
Reed switch can be used in almost all environmental conditions due to the materials used and the hermetically sealed construction. Thus, the
both switches in the contact area are coated with a very hard metal, mostly rhodium or ruthenium (with special switches also tungsten and iridium). This construction will achieve the long service life and reliable working method.

 

The reed switch is available in many different versions. The following parameters are different:

Switching capacity
This is in the range from 0.1 to 30 W. Even a short-term overload already leads to a failure. It should be noted that none of the specified values (voltage, current) will be exceeded for a short time either.

Switching current
This is the maximum permissible current when closing the reed switch. The higher the current, the greater the switching arc on closing and opening. If the current is too high, it can be used for bonding (welding) of the contacts, which means that the function is no longer available. Also capacities of the connected circuit affect the service life of the reed switch negative. For relatively high switching signals, the current should be limited to the first 50 ns. Starting from 50 V and 50 pF, a permanent influence on the reed switch can already occur.

Transport flow
This specifies the maximum permissible current via the already closed contacts. This is higher than the Schaltsrom because the contacts are already closed.

Switching voltage
This is the maximum permissible voltage that the contact is allowed to switch. Switching voltages above the arc limit.

Insulation resistance
The value measured above the open reed switch is typically in the range of 10^9 to 10^14 ohms This good isolation causes only the smallest leakage currents from Femto to Picoampere. Test equipment in which high impedance must be switched between several inputs is therefore feasible.

Contact capacity
This is the capacity between the two open contacts. The values are approx. in the range of 0.1… 0.3 pF. The low contact capacity is a special feature of Reedkontakten. This allows impedance to transmit alternating voltage signals at low overtalk.

Tightening sensitivity
This value specifies the closing point of the switch. It is usually indicated in ampere coils (AWan). A defined measuring coil is used to determine this value. For this purpose, the current of the measuring coil, in which the reed contact to be used is located, is increased to the switch-on point. The calculated value of the sink is then multiplied by the number of coils = tightening sensitivity. The specification is generally valid for 20 °c.

Switching hysteresis
Is the ratio in % between the on and off point

Closing time (incl. bounce)
This is the time required to close the contact (until the end of the bouncing). Most reed switch have a closing time of 100-500 µs.

Release time
This is due to the reed contact in the range between 0.05 and 2 ms.

Switching speed
Up to 300 Hz

Vibration resistance
The mechanical vibration resistance is in the range from 10 to max. 30 G.

Temperature range
Approx.-20 °c… + 150 °c, types also with extended temperature range

normally open (Form A) k_normally open (Form A)
The reed switch is open in the resting position. When a magnet is placed near the switch, the paddles move towards each other – the switch closes. If the magnet is removed, the reed switch will open again.

normally closed (Form B) K_Opener (Form B)

A reed switch closed in a resting position opens when a magnet is brought near and closes when the magnet is removed again.

change over (Form C) K_change over (Form C)

A so-called SPDT (single pole double throw) is a switching contact, which changes from the rest to the working contact when a magnetic field is created.

The reed switch (thus also all products containing these) may only be operatedwithin the electrical limit values specified in the data sheet (switching current, switching voltage, switching capacity). A short-term exceedance of one of these limits can lead to a reduced service life or even to a failure .

the values specified in the data sheets apply to pure ohmic loads ! In most cases, however, the loads are fraught with inductive or capacitive components or lamp loads are switched. In all these cases, the reed contacts must be protectedagainst the occurrence of voltageand current peaks in order to avoid rapid wear or premature failure. See the point protection circuit.

Inductive loads (e.g. motors)

When switching alternating current, an RC link must be connected parallel to the switch and thus in series with the load.

When switching direct current, a freewheel diode must be connected parallel to the load. The polarity must be carried out in such a way that the diode locks at the normal operating voltage and briefly closes the voltage spike which always occurs when the switch is opened.

Capacitive loads
In the case of capacitive loads and lamp loads, increased inrush currents occur which can lead to disturbances up to the welding of the contacts. When switching charged capacitors (e.g. also cable capacities), a sudden discharge occurs, the intensity of which depends on the capacity and the length of the supply line to be considered as series resistor to the switch. The discharge current tip is largely reduced by a series resistance to the capacitor. It should be as large as possible to limit the discharge current to a permissible value.

Incandescent filaments have a resistance in the cold, i.e. in the non-switched state, which is about ten times smaller than in a glowing state. This means that when the power is switched on, if only for a short time a ten times higher current flows than in the glowing, static state of the lamp. This 10-times inrush current surge can be reduced to an acceptable level by means of a series-switched power limiting resistor. One possibility is the ParalleIschaltung of a resistor to the switch, which continuously heats the lamp thread in the switched off state so far that it is not yet glowing.

external magnetic fields can lead to malfunction or permanent changes.

Reed is based on a reed switch that switches when a defined magnetic field is approached. Accordingly, this system is precisely matched to our products. An additional external magnetic field can influence this and lead to malfunctions. Therefore they keep enough distance from magnetic fields, E. G. transformers, Motors,…

By falling or similar shock effects, the function of the sensors and relays can be severely affected, or lead to a failure.

DescriptionHall sensorReed sensor
Sensitivity > 10 Gauss > 5 Gauss
Switching distance Up to 20 mm Up to 40 mm
Power supply Permanently necessary No
Hysteresis Approx. 75% Depending on the application
Switching capacity Few milliwatts Up to 100 watts
Transition resistance > 200 Ohm 0.05 Ohm
Output capacity 100 pF 0.2 pF
Insulation resistance 10^6 Ohm 10^12 Ohm
ESD Sensitivity Yes, requires external protection No
Working temperature 0-70 °c -55-150 °c
DescriptionReed switchMechanical Relay
Life10^10 switching operations 10^10 switching operations
Switching time 0.2-1 ms > 5 ms
Switching voltage Femto-Volts up to 10kV Up to 4kV
Power consumption Approx. 5 mW Approx. 50 mW
Switching current To 3 A Up to 40 A
Insulation resistance Up to 10^14 Ohm Up to 10^9 Ohm

In many of our products permanent magnets are installed. The magnetic material used should be adapted to the respective application.

MaterialFlux densitySpecifics
FerriteLowInexpensive
AlNiCo (aluminium-nickel-cobalt)MeansHigh temperature up to 500 °c
SmCo (Samarium-cobalt)HighHigh temperature stability
NdFeB (Neodymium-iron-boron)Very highKorossionsanfällig