Limit value switches Manufacturers online

Limit value switches (also known as limit switches) are electromechanical components that detect the position of a moving part or a fill level and trigger a specific action as soon as a defined end point is reached.

They are used to convert mechanical movements into electrical signals.

Below you will find the function, types and use of limit value switches as well as a brief overview of their advantages and disadvantages:

How limit value switches work:

A limit value switch typically consists of the following main components:

Actuating element e.g. roller lever, plunger, rotary blade or stylus: This element is mechanically actuated by a moving object or product.

Switching mechanism: A mechanical movement is converted into an electrical contact change.

Housing: Protects the switch from environmental influences (e.g. dust, water, chemical substances).

Electrical contacts (NC contact, NO contact or changeover contact): These contacts switch an electrical circuit when the switch is activated.

Switching principles:

1. normally closed (NC): The circuit is closed and is interrupted when the switch is activated.
2. Normally open (NO): The circuit is interrupted and is closed when the switch is actuated.
3. Changeover contact (CO - Change Over): The switch can switch between two current paths.

Types of limit value switches:

There are different types of limit value switches, which have different mechanisms and designs depending on the application:

1. Mechanical limit switches:
   Limit switches with roller lever, plunger, rotary paddle, float or sensor forks.
   High-precision versions for exact switching points.
2. Inductive/proximity switches:
   Non-contact switches that react to metallic objects.
3. Optical limit value switches:
   Use light barriers or reflectors to determine position.
4. Magnetic switches:
   Work with magnetic fields and react to magnetic objects.
5. Pressure and temperature switches:
   Are used in hydraulic and pneumatic systems.

Use of limit value switches:

Limit value switches are used in many areas, including:

1. Automation technology:
Detecting end positions in machines and conveyor systems.
Safety shutdown in emergency situations.

2. Vehicle technology:
Detecting the position of moving vehicle parts (e.g. sunroofs, trunk lids).

3. Elevators and cranes:
Control of end positions and limitation of movement.

4. Industrial production:
Control of robots, machining centers and presses.

5. Door and gate control:
Detection of open or closed position.

6. Domestic appliances:
Detection of door positions in washing machines or microwaves.

7. Plastics and chemical industry:
overfill protection in granulate and plastic silos.
Control of dosing systems in plastics processing plants.

Advantages and disadvantages of limit value switches:

Advantages:

• High reliability and long service life.
• Mechanical versions do not require an external power supply.
• Versatile use in different environments.

Disadvantages:

• Mechanical wear and tear due to moving parts.
• Limited switching frequency compared to electronic sensors.
• Susceptible to environmental influences such as dust or moisture (except protected designs).

Limit value switches are indispensable components in automation and control technology. Their robust design and simple operation make them ideal for many industrial applications. Despite some limitations, particularly mechanical wear, they remain a cost-effective and reliable solution for position monitoring and safety shutdown.

Here are the most important aspects to look out for when purchasing limit value switches:

When purchasing, various technical, economic and qualitative factors must be considered in order to make an optimal choice.

• Before a purchase decision is made, the technical requirements should be precisely defined.
• Which switching principle and which type of actuation are suitable?
• Normally closed (NC): Switches off when actuated.
• Normally open (NO): Switches on when actuated.
• Changeover contact (CO - Change Over): Can switch between two current paths.
• Different actuating elements are required depending on the application:
• Roller lever: For moving machine parts with sliding or rotating movement.
• Stylus or plunger: For precise end position monitoring.
• Rotary lever: For larger mechanical forces.
• Cable actuation: For emergency stop and safety systems.
• Rotary vane float or oscillating element: For detecting limit levels.
• Limit switches often have to operate under extreme conditions. Important protection types are:
• IP65: Protection against dust and water jets.
• IP67: Protection against temporary immersion in water.
• IP69K: Protection against high-pressure cleaning (e.g. food industry).
• ATEX-certified: Required for potentially explosive atmospheres.
• The mechanical service life indicates how many switching cycles the switch reliably performs, e.g. 1 million switching cycles.
• The switching frequency indicates how many times per second the switch can be actuated, e.g. 10 Hz for fast applications.
• Observe the electrical specifications:
• Operating voltage: AC/DC, e.g. 24V, 110V, 230V.
• Switching current: Important information for the load, e.g. 5A, 10A.
• Switching capacity: Power that the switch can switch e.g. 250V AC, 5A.
• What mounting options should the limit value switch offer?
• Screw mounting: Classic mounting for robust applications.
• Snap-in mounting: For quick and easy installation.
• DIN rail mounting: For space-saving integration in switch cabinets.
• Pay attention to certifications and standards when purchasing: ISO 9001: Manufacturer's quality assurance, IEC/EN 60947-5-1: International standard for industrial switchgear, UL certification: Required for the US market, CE marking: Meets European safety requirements.
• Give preference to high-quality materials such as stainless steel or reinforced plastics for a long service life as well as dust and moisture-resistant designs for demanding environments.
• You should also keep an eye on temperature resistance: Standard models: -10°C to +70°C, special models for extreme environments: -40°C to +150°C.
• Consider the total cost of ownership. In addition to the purchase price, this also includes the costs for maintenance and downtime.
• Compare different suppliers and their guarantees.
• Check whether the desired limit value switch is available immediately or has a longer delivery time.

Professional purchasing of limit value switches requires a detailed analysis of the technical requirements, quality standards and economic aspects. By considering the above criteria, it is possible to ensure that the best choice is made for the application in question.

Limit value switches can be purchased from various suppliers. Comprehensive information about manufacturers and suppliers of Limit value switches from all over the world can be found on Exportpages.