Seven Considerations When Selecting DIN-Rail Terminal Blocks
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Seven Considerations When Selecting
DIN-Rail Terminal Blocks
Top Tips
Know the number of circuit inputs/outputs your application will require.
Consider all aspects of your project for each interface you’ll be making, whether control circuitry, human/
machine interfaces, power supplies, sensors, and/or edge devices required for your automation
interconnections. Starting out with a clear number of circuits will give you a baseline for further selection
criteria you’ll be making.
Understand the types of terminal blocks that are available.
There are seven main types of terminal blocks:
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Feed-through terminal blocks are incorporated when connecting two wires together for wire-to-wire connections.
These blocks have one input and one output per contact and can come in single or multi-level modules.
• Earth/grounding terminal blocks provide electrical grounding to keep people and machinery safe, particularly
in control panel wiring.
• Fuse terminal blocks, as the name implies, provide overvoltage protection to your system so that you do
not damage high-cost devices.
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DIN-rail terminal blocks are used in nearly every industry that
requires hardwired interconnections of some type. Terminal blocks
are used to interconnect a variety of components from human/
machine interfaces, control circuits, motion systems, and more.
These tips will help design engineers understand some of the
characteristics that will make selection easier.
Seven Considerations When Selecting DIN-Rail Terminal Blocks
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• Test terminal blocks provide an easy and safe method to perform testing of the equipment that has been
interconnected into a complete system without disrupting the load circuit of the complete system.
• Distribution terminal blocks are used in multi-phase systems where various I/O congurations may be
present. They are used primarily to simplify the interconnections in a distributed system.
• Thermocouple terminal blocks are specically designed for temperature measuring circuits where very
small voltages are used.
• Electronic terminal blocks provide isolation between the printed circuit board and other components in
the system. They are used as indicators or for test circuits.
Know what accessories you might need for your application.
Depending on the type of application you are working on and the industry it will go into, you may need a
variety of accessories. Some items to consider include end stops to prevent the terminal blocks from shifting
on the rail, endplates to cover open terminals for safety reasons, and separator plates to separate circuits
visually. Jumpers and shorting links are available to interconnect two or more terminals, while protective
covers are used for uninsulated parts. Other accessories include test plugs for handsfree troubleshooting
and testing plus marking tags for identifying the terminals.
Calculate the current and voltage of the wires you’ll require for each terminal block.
There are three primary concerns you’ll want to think about when it comes to your system. You’ll want to know
the voltage and current ratings for each component, the wire sizes you’ll require to handle those ratings, and
the torques you will need to maintain connection when under potentially hazardous conditions.
Know the operating temperature of the equipment you are designing.
When considering your application, identify where it will be operating and under what temperatures. If not
calculated properly, over-temperature values can stress your equipment and cause early failures.
Plan your design with a clear understanding of the types of wires you will be using.
Dierent types of equipment need dierent types of wire for their interfacing. You don’t want to mix solid
and stranded wires without the right understanding of your project needs. The three wire types you’ll be
using are solid wires, stranded wires, and wires using ferrules. Multiple-sized wires and ferrules should be
considered dependent on the application.
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Seven Considerations When Selecting DIN-Rail Terminal Blocks
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Be clear on the three types of connection technologies that can be incorporated.
Common DIN-rail terminal blocks use screw clamp or spring/cage clamp technology for quick and easy
installation and maintenance. In addition, push-in DIN-rail terminal blocks are nding a solid hold in the
industry as well.
• Screw type terminals are the most dependent on human interaction because of the need to physically
screw the terminals. They have been in circulation the longest and oer simple operation. Most screw type
terminal blocks oer a locking mechanism to guarantee a safe connection.
• Spring/cage type terminals are typically used inside machine control enclosures where human involvement
is expected to happen less often than with screw type terminal blocks. A screwdriver or other tool is needed
to open a preloaded spring. Once removed, the stainless steel spring pushes the wire conductor against a
copper/tin-plated current bar for electrical connection. Because this type of terminal has a natural resistance
to shock and vibration, they are used in vehicles, elevator cabinets, and other moving equipment. Due to
their operation, spring/cage type terminal blocks are especially useful when stranded wire is used.
• Push-in type terminal blocks provide a toolless capability that is attractive in many industrial applications
where large numbers of terminal blocks are installed. Users are able to simply push solid wires or stranded
wires with ferrules into the terminal block for a reliable connection. These terminal blocks are ideal for
automation and robotic wiring applications.
Partner with a stable industry supplier that has experience with terminal block selection.
Working with the right supplier as a partner is always a benet. An experienced supplier can often help
your design engineers in their selection process, particularly with complex equipment that may be sold
around the world.
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