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A cable shield reduces interference only when its construction suits the installation and the shield has a continuous, low-impedance connection. There is no universal rule to ground every shield at one end or both: use the grounding method specified for the equipment and signal, and account for the installation’s bonding arrangement.
What does a cable shield do?
A cable shield is a conductive layer around signal conductors that attenuates coupled electrical, magnetic, or electromagnetic interference. As Siemens puts it, “Shielding is a measure to attenuate (dampen) magnetic, electrical or electromagnetic interference fields.” The shield also needs a suitable low-impedance path for interference current; a shield that is disconnected, poorly bonded, or terminated with a high-impedance connection may not perform as intended.
Siemens SIMATIC ET 200eco PN Manual Collection V20, published November 2024, describes this function and emphasizes a low-impedance protective-conductor connection.
How do foil, braid, and combined shields differ?
Choose a construction for the signal’s interference environment, cable movement and strain, connector or clamp method, and the equipment maker’s installation requirements. The cited guidance does not establish a standardized effectiveness ranking that makes one construction best for every job.
#1 Best Overall
- SPECIFICATIONS: 18AWG 4 conductor shielded wire, Rated voltage: 300V, Rated temperature: 80℃/176℉, Resistance: ≤ 23.2Ω/KM20℃. Current: 8.6A. Conductor: Tinned Oxygen Free Copper. Insulation: PVC. Shield: Tinned Copper + AL, OD:6.6±0.25mm, UL Listed
- HIGH CONDUCTIVITY: UL2464 18 gauge 5 conductor shielded cable, each cable consists of 34 strands of 0.18 mm tinned oxygen-free copper stranded. It is characterized by high conductivity, low resistance, ultra-low eccentricity and oxidation resistance
- EXCELLENT SHIELDING: This UL2464 CNC shielded cables are double shielded (aluminum + tinned copper) for superior interference immunity with up to 85% shielding. In addition, the shielding serves as a safety protection for the internal cables
- DURABLE MATERIAL: The 18/5 shielded wire has a PVC jacket of uniform thickness. It is flame retardant, safe and stable, anti-aging, acid and alkali resistant, easy to bend, etc. Flame retardant passes the test standards of VW-1 and FT1
- WIDELY APPLICATION: Our 18 gauge shielded cables have excellent data signal transmission capability and efficient conductivity, and are widely used in CNC devices, stepper motors, 3D printers, security and alarm systems, sound, speaker, and so on
| Construction | Practical considerations | What the cited guidance establishes |
|---|---|---|
| Braid | Can support a clamp-style termination; confirm suitability for the cable and equipment. | Siemens and SEW-EURODRIVE recommend braid in their respective guidance. SEW-EURODRIVE recommends braid coverage above 80%; that is its recommendation, not a universal standard or a shielding-effectiveness measurement. |
| Foil | Consider how the cable will be fastened and whether it will experience tensile or compression strain. | Siemens warns that strain can damage foil-shielded cable at the fastening point and reduce shielding effect. This does not mean all foil shields are unsuitable. |
| Foil and braid combined | May be a specified construction option; performance still depends on correct installation and termination. | LAPP documents network cable screened with braid and aluminum-laminated foil. This does not guarantee performance in every installation. |
Siemens also recommends more than 80% contact at the contact point for the installation covered by its 2024 manual. That figure is not a universal performance score and should not be confused with shielding effectiveness in decibels.
Should a cable shield be grounded at one end or both ends?
It depends on the signal, equipment, and grounding design. Some instructions call for both-end grounding, especially for high-frequency interference; others specify single-point grounding for particular systems or signals. Follow the applicable equipment documentation rather than applying one method to every cable.
Rank #2
- SPECIFICATIONS: 22AWG 3 conductor shielded wire, Rated voltage: 300V, Rated temperature: 80℃/176℉, Resistance: ≤ 59.4Ω/KM20℃. Current: 3.4A. Conductor: Tinned Oxygen Free Copper. Insulation: PVC. Shield: Tinned Copper + AL, OD:4.9±0.18mm, UL Listed
- HIGH CONDUCTIVITY: UL2464 22 gauge 3 conductor shielded cable, each cable consists of 17 strands of 0.16 mm tinned oxygen-free copper stranded. It is characterized by high conductivity, low resistance, ultra-low eccentricity and oxidation resistance
- EXCELLENT SHIELDING: This UL2464 CNC shielded cables are double shielded (aluminum + tinned copper) for superior interference immunity with up to 85% shielding. In addition, the shielding serves as a safety protection for the internal cables
- DURABLE MATERIAL: The 22/3 shielded wire has a PVC jacket of uniform thickness. It is flame retardant, safe and stable, anti-aging, acid and alkali resistant, easy to bend, etc. Flame retardant passes the test standards of VW-1 and FT1
- WIDELY APPLICATION: Our 22 gauge shielded cables have excellent data signal transmission capability and efficient conductivity, and are widely used in CNC devices, stepper motors, 3D printers, security and alarm systems, sound, speaker, and so on
When guidance specifies both ends
ABB’s guidance says shielded data cables should be grounded at both ends. In the context it describes, grounding at one end protects against capacitive interference and low-frequency disturbances only. ABB also advises connecting the shield directly with a clip at the cabinet entry and using metallic or metal-plated connectors for shielded data connections. ABB’s cable-shield guidance is specific to its described installation context.
SEW-EURODRIVE recommends grounding both ends for high-frequency interference. It identifies exceptions where a one-sided connection may be preferable, including some very low-level analog signals or cases where equipotential bonding cannot be routed. It also warns that a potential difference between grounding points can drive compensating current through the shield. See SEW-EURODRIVE’s shielding guidance for its conditions and exceptions.
Rank #3
- SPECIFICATIONS: 22AWG 2 conductor shielded wire, Rated voltage: 300V, Rated temperature: 80℃/176℉, Resistance: ≤ 59.4Ω/KM20℃. Current: 3.4A. Conductor: Tinned Oxygen Free Copper. Insulation: PVC. Shield: Tinned Copper + AL, OD: 4.7±0.18mm, UL Listed
- HIGH CONDUCTIVITY: UL2464 22 gauge 2 conductor shielded cable, each cable consists of 17 strands of 0.16 mm tinned oxygen-free copper stranded. It is characterized by high conductivity, low resistance, ultra-low eccentricity and oxidation resistance
- EXCELLENT SHIELDING: This UL2464 CNC shielded cables are double shielded (aluminum + tinned copper) for superior interference immunity with up to 85% shielding. In addition, the shielding serves as a safety protection for the internal cables
- DURABLE MATERIAL: The 22/2 shielded wire has a PVC jacket of uniform thickness. It is flame retardant, safe and stable, anti-aging, acid and alkali resistant, easy to bend, etc. Flame retardant passes the test standards of VW-1 and FT1
- WIDELY APPLICATION: Our 22 gauge shielded cables have excellent data signal transmission capability and efficient conductivity, and are widely used in CNC devices, stepper motors, 3D printers, security and alarm systems, sound, speaker, and so on
When instructions specify single-point grounding
For the Schneider Electric TM5 system, the instructions call for shielded, properly grounded cable for analog, high-speed I/O, and communications. The stated default is single-point grounding; multipoint grounding is permissible on a properly dimensioned equipotential ground plane. This is guidance for that system, not a general rule for unrelated equipment. Consult Schneider Electric’s Machine Expert V2.1 system-grounding instructions.
How should you terminate a cable shield?
The aim is a secure, low-impedance connection that preserves shield continuity when the shield serves functional EMC purposes. A long, thin wire connection can have more impedance than a broad, direct contact, particularly at higher frequencies. Use the termination method specified for the cable and equipment.
Rank #4
- PRODUCT SPECIFICATION -- 100FT 22 Gauge 2 Conductor Shielded Plenum Cable. Rated voltage: 300V. Rated working temperature from -10℃/14℉ to 80℃/176℉.
- HIGH CONDUCTIVITY -- MOOKEERF 22 AWG shielded wire is built with stranded pure copper conductor,which has better conductivity,lower resistance and corrosion resistance than CCA (copper clad aluminium),providing maximum conductivity and reliability to ensure that your fire alarm systems run smoothly.
- CMP PLENUM-RATED CABLE -- Our low voltage electrical wire use flame retardant materials for improved safety,ensuring optimal pressure resistance and good fire performance attributes.It features a CMP/CL3P/FPLP (Plenum-Rated) flame-retardant rating that provides peace of mind in case of fire.
- EASY TO USE -- Stranded pure copper offers a variety of benefits when compared to solid wiring. Our security alarm control cable is flexible enough to be bent arbitrarily and can be comfortably fitted even in narrow corners,reducing entanglement during installation.
- WIDELY APPLICATION -- The 22 gauge 2 conductor alarm control wire is widely used for wiring fire alarm, security burglar alarm, public address systems, intercoms, walkie talkies, telephone stations, communications, instrumentation, access control, nurse call, security and other low voltage applications.
- Check the equipment instructions. Confirm whether the shield should be grounded at one end or both, where it should be bonded, and which connector or clamp is approved.
- Make contact near the cabinet or system entry when specified. ABB recommends a direct clip connection at cabinet entry. Schneider Electric describes a clamp contacting exposed shield close to the system base and secured to a conductive backplane.
- Use a compatible clamp or connector. Confirm that it fits the cable diameter and makes contact with the exposed shield and required conductive surface. ABB recommends metallic or metal-plated connectors for the shielded data connections it covers.
- Maintain broad, low-impedance contact. LAPP says a correctly made connection over as large an area as possible helps keep impedance low. Siemens’ more-than-80% contact recommendation applies to its referenced installation, not to every cable or installation.
- Protect the shield from damage. Fasten the cable without imposing damaging tensile or compression strain, especially where foil-shielded cable is used, as Siemens cautions.
See LAPP’s overview of shielded cables and EMC connection systems and its shielding information for additional construction and connection context.
How should shielded cables be routed?
Where practical, route communication and I/O cables separately from power cables to reduce opportunities for interference coupling. Schneider Electric includes this separation in its TM5 system guidance. Preserve the shield’s continuity through the installation when it provides functional EMC shielding, and follow the equipment instructions for connectors, cabinet entry, and bonding.
Best Value
- Cost-Effective: The use of Copper-Clad Aluminum (CCA) reduces material costs, making this cable an economical option for projects with budget constraints..
- Lightweight and Easy to Install: The lightweight nature of CCA makes this cable easy to handle and install, minimizing installation time and effort.
- Excellent Electrical Conductivity: This 18 AWG cable provides excellent electrical conductivity, ensuring that your signals and data transmission are reliable and interference-free.
- Durability: The cable is designed to withstand environmental conditions, and the CCA core is resistant to corrosion, ensuring long-lasting performance.
- Versatile Applications: With 2 conductors and a 18 AWG thickness, this cable is suitable for a wide range of low-voltage applications, including alarm systems, intercoms, and other communication networks.
What should you check before selecting shielded signal cable?
- Signal type: Identify whether the cable carries analog, high-speed I/O, data, or communications signals; grounding instructions may differ.
- Conductors and electrical characteristics: Match conductor or pair count and the cable’s electrical specifications to the equipment.
- Interference environment: Consider the interference sources and frequency range relevant to the installation; the cited sources do not provide a universal construction ranking.
- Mechanical demands: Account for cable movement, flex, fastening, tensile strain, and compression.
- Termination details: Check the connector, clamp, cable diameter, mounting surface, and shield-contact requirements.
- Equipment requirements: Use the grounding and installation method specified by the equipment manufacturer and the system’s grounding design.
“Shielded signal cable” is a broad product-search phrase, not a complete specification. A cable shield grounding clamp can be an appropriate accessory where the installation permits that termination method; confirm its compatibility with the cable and mounting surface.
Quick Recap
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