In industrial machinery and compact tank systems, reliable level control is essential for safe operation, pump protection, alarm generation and process continuity. Applications such as hydraulic oil tanks, small storage tanks, machinery reservoirs and auxiliary tanks require level switches that are easy to install, economical and durable.
The ELM 31, ELM 41 and ELM 51 level switches are designed for these needs. As part of the ELM magnetic float level switch series, these models provide practical on/off level detection with compact dimensions, stainless steel construction and simple cable connection.
What Are ELM 31, ELM 41 and ELM 51?
ELM 31, ELM 41 and ELM 51 are vertical type level switches used for tank level control. They are especially preferred by machine manufacturers because of their ease of use, economical design and compact structure.
Their small dimensions allow installation in limited spaces, while stainless steel wetted parts make them suitable for use with various industrial liquids. These models are practical solutions for minimum or maximum level detection in small and medium-sized tank applications.
Operating Principle
The ELM series operates with a magnetic float and reed sensor principle. A magnet inside the float moves according to the liquid level. When the magnetic field reaches the reed sensor inside the tube, the electrical circuit opens or closes.
When the float moves away from the reed sensor, the contact returns to its original position. This signal can be used directly or evaluated through a relay circuit for pump control, alarm output, filling, emptying or automation applications.
Vertical Mounting Design
ELM 31, ELM 41 and ELM 51 are designed for vertical mounting. This makes them suitable for installation from the top or bottom of a tank, depending on the required switching point and tank design.
The vertical structure is ideal for applications where side mounting is not suitable or where the tank geometry requires a compact level switch. Their simple mechanical design supports fast installation and practical commissioning.
Model Differences
ELM 31 is the most compact model in this group. It has a cylindrical float design, an S1Y float type and a maximum pressure rating of 10 bar. It is suitable for applications where limited space, economical design and simple level detection are the main priorities.
ELM 41 has a larger spherical float design with S2A float type. It offers a maximum pressure rating of 30 bar and higher electrical contact capacity compared to ELM 31. It is suitable for applications requiring a more robust float structure while still maintaining compact dimensions.
ELM 51 uses S4A / S40A float options and has a larger spherical float structure. It also provides a maximum pressure rating of 30 bar and is suitable for applications where a larger mechanical connection and stronger float design are required.
Technical Features
All three models are designed for vertical mounting and cable electrical connection. Each model has one standard float and one contact output.
ELM 31 has 304 stainless steel as standard for float, wetted parts and tube material, with 316 stainless steel available as an option. ELM 41 and ELM 51 use 316 stainless steel float material, while wetted parts and tube material are 304 stainless steel as standard, with 316 stainless steel available as an option.
The maximum operating temperature for all three models is 125 °C. The minimum liquid density is 0.80 g/cm³. All models can be used with the optional SK-P2 liquid level relay.
Electrical Specifications
ELM 31 provides 1 x SPST-NO contact output, 1 A contact current, maximum contact power of 10 W / VA and maximum supply voltage of 200 VDC / 140 VAC.
ELM 41 and ELM 51 provide 1 x SPST-NO contact output, 1.5 A contact current, maximum contact power of 50 W / VA and maximum supply voltage of 200 VDC / 250 VAC.
This makes ELM 41 and ELM 51 suitable for applications requiring higher contact capacity, while ELM 31 is ideal for smaller and lower-power control circuits.
Mechanical Connection Options
ELM 31 and ELM 41 are available with R 1/8" or M10x1 mechanical connection options. These compact connections make them suitable for small tanks and machinery applications.
ELM 51 is available with R 3/8" or R 1/2" mechanical connection options. This larger connection structure provides a more robust installation option for applications requiring a bigger float and higher mechanical strength.
Application Areas
ELM 31, ELM 41 and ELM 51 are suitable for machinery, hydraulic oil tanks, small storage tanks and similar liquid level control applications.
They can be used for high-level alarm, low-level alarm, pump protection, dry-run protection, tank filling control, emptying control and general liquid level monitoring. Their compact structure makes them particularly useful in OEM machinery and equipment manufacturing.
Advantages of ELM 31, ELM 41 and ELM 51
The main advantages of these models are their economical design, easy installation, compact dimensions and stainless steel construction.
Because they use magnetic reed switch technology, they provide simple and dependable level detection without complex electronics. Their cable connection allows easy integration into control panels, relays and PLC systems.
The availability of different float sizes, pressure ratings and mechanical connections makes it possible to select the most suitable model according to the tank size, liquid type and control requirement.
Optional SK-P2 Liquid Level Relay
The ELM 31, ELM 41 and ELM 51 models can be used with the optional SK-P2 liquid level relay. This allows the contact signal from the level switch to be evaluated in control panel applications.
With SK-P2, the level information can be used for start-stop control, alarm functions, pump control and other automation scenarios. This provides additional flexibility for system integrators and machine manufacturers.
Why Choose the Right Model?
Choosing between ELM 31, ELM 41 and ELM 51 depends on the application requirements.
ELM 31 is suitable for compact, economical and lower-pressure applications. ELM 41 is a good choice when a larger float and higher pressure rating are needed while keeping the connection size small. ELM 51 is preferred when a larger float, stronger connection size and robust vertical level control are required.
By selecting the correct model, users can achieve reliable level detection with the right balance of size, pressure rating, connection type and electrical capacity.
Conclusion
ELM 31, ELM 41 and ELM 51 level switches provide compact, economical and reliable solutions for vertical tank level control. With stainless steel wetted parts, magnetic reed switch operation, cable connection and optional SK-P2 relay compatibility, they are suitable for a wide range of machinery, hydraulic tank and small reservoir applications.
Their simple structure, easy installation and different model options make them practical choices for machine manufacturers and industrial users looking for dependable liquid level control.