Complete guide to instrumentation cables

Instrumentation cables are highly durable, flexible and reliable cables that are designed to carry signals from instrumentation and control equipment across a wide range of industries, including the marine industry, manufacturing industry, petrochemical industry and more. These cables feature unique properties to ensure they can handle signal transmission reliably, even in harsh environments.

Instrumentation cables are also incredibly versatile, and can be used for almost any application involving the transmission of voice and data. This is why you can find these cables in many types of devices across a wide range of industries. However, this also means that these cables often need to be custom-built to suit a particular application, even if this just involves tweaking a basic cable design.

Here at Custom Designed Cables, we’re industry-leading experts in the design and manufacture of custom cables, including custom instrumentation cables for a variety of sectors. We have the breadth of experience required to handle almost any instrumentation-related project, but if you’re not exactly sure what you need, you may find it difficult to work on your design enquiry in the first place.

This is why we’ve created a complete guide to instrumentation cables. Keep reading to gain a comprehensive overview to inform your next cable design project.

What is an instrumentation cable?

As briefly explained, instrumentation cables are designed for reliable signal transmission and process control applications. This can be in a wide variety of environments, but you’ll commonly find instrumentation cables used for industrial process control in factories, where they will connect instruments and electrical equipment and carry signals between them.

In these industrial environments, instrumentation cables are designed to cater to low-power field-driven signals and data. This makes them useful for gathering and relaying accurate signals when connecting sensors and measuring devices to control units, allowing them to ensure reliable data transmission in these setups. This is extremely important in environments where the reliability and accuracy of signal transmission is essential for data precision and process control.

Since these cables are often used in harsh industrial environments, they also have to be able to resist a lot of external complications and interference that could potentially destabilise essential processes, including temperature fluctuations, electrical interference, chemical exposure, rough handling, mechanical stress, and wear and tear. We’ll discuss how the properties and construction of instrumentation cables enable them to do this later, but first, let’s clear up some confusion about instrumentation cables and other popular types of industrial cables.

Instrumentation cable vs control cable

Instrumentation cables are often confused with control cables, as they are both industrial cables used for measurement and control applications. However, while instrumentation cables are mainly designed to transmit low-energy data or communication signals, control cables are designed to carry power signals to control or operate machinery. 

Since control cables are designed for power transmission rather than signal transmission like instrumentation cables, they can handle higher voltages and currents. They are also manufactured to resist harsh environmental conditions such as extreme temperatures to ensure safety when powering equipment. Instrumentation cables are designed for harsh industrial environments too, but their focus is more on ensuring accurate, interference-free signal and data transmission. This is achieved through cable shielding technology.

Instrumentation cable vs power cable

As instrumentation cables are used for the reliable transmission of voice, data or low-voltage power in a range of environments (including industrial), they are quite different from power cables or electrical cables, which are designed to power many types of machinery and devices, including industrial equipment, lighting, household appliances, and much more. Power cables are built to handle a variety of voltages and currents to safely support power infrastructure for many different applications, and they require insulation and grounding to work properly. Instrumentation cables are more flexible, lightweight and need cable shielding to eliminate signal interference.

How is an instrumentation cable constructed?

Instrumentation cables have many properties that enable them to be used reliably in harsh industrial environments, including resistance to temperature fluctuations, resistance to abrasion and wear and tear, durability, flexibility (to enable use in a variety of environments and setups), resistance to mechanical stress, signal integrity and more. These fantastic properties are the result of instrumentation cables’ unique construction, which consists of:

  • A conductor – This is either a bare or tinned copper wire in stranded form (many wires twisted together) or solid form. The conductor allows the flow of electrical current through the cable. Instrumentation cables can have multiple conductors.
  • Insulation – An insulating material, such as PVC, PE or XLPE, is applied around the conductor to prevent the current from leaking out and to also protect the conductor from environmental threats such as water or temperature fluctuations. Insulation ensures safety, signal integrity and efficiency.
  • Cable shielding – A fine wire mesh, weave or braid (or sometimes a material like aluminium foil) is applied over the conductors and insulation to reduce electromagnetic interference (EMI). 
  • Drain wire – Drain wires are added to shielded cables for grounding, as a drain wire provides a low-resistance connection to the cable’s shield to protect the cable from electrical surges. 
  • Inner sheath – This is an optional component that covers the shielded conductors and drain wire to keep everything together and provide more protection against environmental factors and wear and tear.
  • Armour – Another optional component is cable armouring, which provides enhanced mechanical protection for harsh environments and applications. The cable armour consists of a layer of steel wires that are either wrapped or braided around the internal construction depending on your mechanical strength vs flexibility needs. To learn more about armoured cables, check out our article on the differences between GSWB and SWA cables.
  • Outer sheath – This is the final layer that holds everything together and protects the internal components. Multiple individual cables or ‘cores’ can be bundled together inside a single outer sheath, creating a large multi-core cable. Multi-core cables are able to transmit multiple signals simultaneously, making them extremely useful in the telecommunications and audio visual industries.
inside of a cable

Since instrumentation cables are incredibly versatile and can be used for a wide variety of applications, they’re often custom-built to suit a specific purpose. This can either be a significant project or could simply involve taking a basic instrumentation cable design and making some tweaks, such as adding more cores, adding cable armour or changing the insulation material.

Common materials used

Different materials can have various effects on the end product, making the cable suitable for different kinds of applications and environments. Here are some of the most commonly used materials in instrumentation cable construction and their properties:

  • PVC (polyvinyl chloride) – PVC can either be used as a cable sheathing material or as an insulating material. PVC is flame-retardant and resistant to a wide range of chemicals. It can be used for indoor and outdoor applications, direct burial, and environments with temperature fluctuations.
  • LSZH (Low Smoke Zero Halogen) – LSZH sheathing is used as a safer alternative to PVC in projects where potential fires could pose a significant threat to life, such as projects in public and residential areas. LSZH is more fire-resistant and does not produce toxic halogen gas if it does start to burn.
  • PE (polyethylene) – Like PVC, PE can also be used as a sheathing or insulating material. It has superior mechanical strength, chemical resistance and resistance to low temperatures, but the trade-off is that PE is more rigid and isn’t flame-retardant. Due to this fire risk, PE is usually used for outdoor applications and direct burial.
  • XLPE (cross-linked polyethylene) – XLPE has even better chemical resistance and temperature resistance. It’s often used as an insulation material.
  • SWA (steel wire armour) – This type of cable armouring improves mechanical strength with a layer of galvanised steel wires wrapped around the cable components, providing maximum coverage and protection at the expense of flexibility.
  • GSWB (galvanised steel wire braid) – Steel wires are braided around the cable core rather than wrapped, which offers slightly less coverage and mechanical protection but more flexibility.
  • Silicone rubber – This can be used as an insulating material when resistance to extended temperature ranges is needed.
  • Metal tape – Steel or brass metal tape can be wrapped around the insulated cable cores to provide inductive protection and rodent protection. It’s a very high-coverage but inflexible type of cable armouring.
  • Mica tape – This is an insulating material that’s often used in fire-resistant cables.
  • Lead or lead alloy sheathing – This type of cable sheathing is particularly useful in environments where enhanced protection against oils and chemicals is needed, e.g., in polluted mud.

What are instrumentation cables for?

Instrumentation cables are incredibly versatile and can be found in many industries. Here are just a few examples:

Factories

Instrumentation cables are perhaps most commonly found in industrial environments like plants and factories, where they’re used to connect instruments and electrical equipment. In any situation where processing and data transmission operations need to be measured and controlled using electrical equipment, you’ll find instrumentation cables being used to transmit data efficiently and reliably. Plus, since these cables are designed for harsh environments with temperature fluctuations, chemical exposure, and the potential for rough handling, they can be relied upon to keep these process control systems running smoothly.

Medical equipment

Larger multi-core instrumentation cables are frequently used for larger and more complex machinery, such as medical machines like MRI scanners. Reliable signal transmission is absolutely vital in medical settings, as this ensures all data and processes are handled accurately.

Monitoring electrical systems

Monitoring is extremely important in electrical power systems for safety, compliance, efficiency and reliability. Instrumentation cables are used to monitor these systems to ensure that these systems and their associated processes are running as they should.

Small devices

In addition to being used for complex machinery, instrumentation cables can also be used for an incredible range of smaller devices you’d find around your home. Anything that involves the transmission of data will likely use instrumentation cables, including small voice transmission devices like handheld walkie-talkies. Of course, these household instrumentation cables will be much smaller to fit in these devices, but the basic properties will be very similar.

Benefits of instrumentation cables

If you’re not already convinced of the importance of instrumentation cables, here are some of the amazing benefits they offer:

1. Signal integrity

Perhaps most importantly, instrumentation cables transmit signals and data reliably in process control applications, where consistent precision is paramount. Instrumentation cables are shielded against EMI and other external factors like chemical exposure and temperature fluctuations, which means they can operate extremely reliably even in harsh industrial environments.

2. Durability

Since they’re often designed for use in factories, instrumentation cables are very robust, durable and long-lasting. Standard PVC instrumentation cables are already durable enough to withstand bending, mechanical stress, and wear and tear, but you can also customise your cables with additional cable armouring to make it strong enough for the toughest of applications, including direct burial.

3. Flexibility

Instrumentation cables are both strong and flexible, making them ideal for even the most awkward configurations. Flexible PVC or silicone rubber sheathing can be used to enhance the flexibility of these cables further.

4. Lightweight

Depending on the exact construction of your instrumentation cable, it can be very lightweight and easy to install. Thicker multi-core cables with added armouring will naturally be heavier and less easy to manoeuvre, but if needed, you can customise your instrumentation cables to prioritise easy handling.

5. Versatile

Instrumentation cables can be used for signal transmission and process control across a huge range of industries, environments and applications. Plus, since they can be custom-built to suit your specific needs, you can design the perfect instrumentation cables for your projects, using the right materials, dimensions, and even your company branding for the cable jacketing.

Looking for an instrumentation cable manufacturer? At Custom Designed Cables, we design and supply instrumentation cables for a wide variety of industries, using our extensive experience to manufacture high-quality cables that comply with national or international standards where appropriate. Contact us today for a quote!