Tag Archives: Industrial Connectivity

What is Industrial Connectivity?

Engineers include any component involved in the path of delivering control signals or power for doing useful work as part of industrial connectivity. Typically, components such as terminal blocks, connectors, motor starters, and relays are part of industrial connectivity.

Engineers divide industrial connectors into four categories depending on the environments in which they operate—commercial, industrial, military, and hermetic. Commercial applications do not consider temperature and atmosphere as critical operating factors affecting performance. Industrial applications require connectors capable of handling more rugged environments involving hazards such as sand, dust, physical jarring, vibration, corrosion, and thermal shock.

Most general connectors use low-cost materials to merely maintain electrical continuity. However, designers have a large variety of materials from which to choose for making connectors. These include brass, beryllium copper, nickel-silver alloys, gold, gold-over-silver, gold-over-nickel, silver, nickel, rhodium, rhodium-over-nickel, and tin.

No wire preparation is necessary for use in terminal blocks. The user only needs to strip the insulation and install the wire using a screwdriver. One can use a wide range of wire sizes with terminals that provide an easy way to hookup wires from different components, ensuring fast connection/disconnection during troubleshooting and maintenance.

Manufacturers make terminal bodies from a copper alloy with the same expansion coefficient as the wire it connects. This prevents uneven expansion from causing loosening between the connector screws and the wire, avoiding an increase in contact resistance. Using similar metals also avoids corrosion, usually with two different metals in contact, as a result of electrolytic action between them.

SSRs or Solid-State Relays control load currents passing through them. For this, they use power transistors, SCRs, or silicon-controlled rectifiers, or TRIACs as switching devices. Engineers use isolation mechanisms such as optoisolators, reed-relays, and transformers for coupling input signals to the switching devices to control them.

To reduce the voltage transients and spikes that load-current interruptions typically generate, engineers use zero-crossing detectors and snubber circuits, incorporating them within solid-state relays.

Semiconductor switches generate significant amounts of waste power, and engineers must minimize their operating temperature using heat sinks attached to solid-state relays. SSRs can operate in rapid on/off cycles that would wear out conventional electromechanical relays quickly.

Electromechanical relays physically open and close electrical contacts for operating other devices. In general, they cost much less than equivalent electronic switches. They also have some inherent advantages over solid-state devices. For instance, the input circuit in electromechanical relays is electrically isolated from the output circuits, and one relay can have more than one output circuit, each electrically isolated from the others.

Furthermore, the contact resistance offered by electromechanical relays is substantially lower than that offered by a solid-state relay of a similar rating. The contact capacitance is lower as well, benefitting high-frequency circuits. Compared to solid-state relays, electromechanical relays are far less sensitive to transients and spikes, not turning on as frequently as SSRs do. Brief shorts and overloads also damage electromechanical relays to a far less extent than the damage they cause to SSRs.

Improved manufacturing technology is now making available electromechanical relays in small packages suitable automated soldering for PCB mounting and surface mounting.

What Influences Industrial Connectivity?

In the industry, any component coming in the path of delivering control signals or power to do useful work is termed industrial connectivity. For instance, components including relays, motor starters, terminal blocks, and connectors are all typical connectivity components.

Generic connectors can use low-cost material as they merely maintain electrical continuity. However, based on operating environments, connectors are differentiated into four categories: hermetic, military, industrial, and commercial. While hermetic connectors offer maximum exclusion of their inner structural materials from the elements, military and industrial connectors handle more rugged environments with hazards including thermal shock, vibration, corrosion, physical jarring, dust, and sand. Most commercial applications do not make such extreme demands of connectors, and therefore, atmospheric and temperature conditions are the least critical factors that affect the performance of commercial connectors. This allows designers to select from different connector materials.


This is a metal alloy made from copper and zinc, with manufacturers varying the proportions to create varying properties. Although brass has excellent conductivity, it cannot withstand abrasion from many cycles of insertion and withdrawal. It undergoes crystallization under repeated stress and loses flexibility as it ages. Suitable for non-critical and low-contact-force applications, it is easy to braze, weld, solder, and crimp brass.

Beryllium Copper

With excellent electrical, mechanical, and thermal properties, beryllium copper easily resists corrosion and wear. Among all copper-based spring alloys, beryllium copper is stronger and more resistant to fatigue, while able to withstand repeated insertion and withdrawal cycles. However, it is the most expensive among all basic contact materials.

Nickel-Silver Alloys

Not always requiring plating, nickel-silver alloys resist oxidation. While contacts made of nickel-silver alloys are susceptible to stress corrosion, the extent does not exceed that of brass.


Gold, a highly stable plating material, is an excellent conductor inferior only to silver and marginally so to copper. With the lowest contact resistance and providing the best protection from corrosion, manufacturers use hard gold plating for contacts experiencing frequent insertion/withdrawal cycles. For even greater frequency of cycling, gold impregnated with graphite offers only a slight increase of contact resistance.


A general-purpose plating metal for power contacts, silver has a poor shelf life and tarnishes when exposed to the atmosphere. Although this increases the contact resistance, the oxide coating does not affect contacts carrying higher currents.


With good corrosion resistance, nickel offers low contact resistance and fair conductivity. Therefore, it is used as an undercoat to prevent migration of silver through gold in high-temperature environments. Although it has good wear resistance, nickel may crack during crimping unless properly plated onto the base material.


Manufacturers use rhodium for contacts that need exceptional wear qualities. Although conductivity of rhodium is lower than that of gold or silver, the higher resistance is acceptable for thin coatings.


Providing good conductivity and excellent solderability, tin offers a low-cost finish and poor wipe resistance. This makes it the most suitable for connections requiring only very few mating cycles. Tin, not being a noble metal, will corrodes easily.


This is a widely used plating combination as it offers the surface qualities of gold, while minimizing the amount of gold required. The hard under-plating of nickel prevents migration of the base metal.