A shielded cable gland is only as good as the bond it makes to the cable screen. You can order the right part number, seal it to IP68, and still lose most of the screening because the braid was twisted into a pigtail or the gland landed on a painted enclosure wall. The gland is not a fitting that happens to be metal — it is the point where the screen stops being a wrap of copper and becomes part of the enclosure potential.

This guide covers the cable side of that decision: how the common screen constructions behave, which termination geometry holds up at radio frequencies, when to bond at one end or both ends, and how to size a gland without trapping yourself. The gland’s own mechanism is covered in our article on what an EMC cable gland is and how it works.

Why a Shielded Cable Needs a Different Gland

A standard metal gland seals, grips and provides strain relief. What it does not guarantee is a low-impedance circumferential path from the screen to the enclosure — many designs have no component shaped to press against a braid.

Screening works because the screen carries interference current back to its source as a return current flowing over its outside surface, and that only happens while the screen behaves like a continuous conductor. Introduce a break — a length of thin wire, a loose spiral, an unpainted gap — and the bond acquires series inductance that increasingly blocks the interference current as frequency rises. The screen stops behaving like a short circuit and starts behaving like an antenna. Published cable-assembly measurements routinely report a 20–40 dB improvement above 100 MHz when a pigtail bond is replaced by a full circumferential bond on the same cable. Coverage percentage and shield material matter far less than that single decision.

An EMC gland earns its place by providing a clamping surface that touches the screen around its whole circumference, close to the enclosure sheet.

The Four Screen Constructions You Will Actually Meet

Termination technique has to follow construction. A gland that is perfect for a braid can be useless on a foil.

Two of these are frequently confused. Foil is a continuous wrap, so it presents no apertures to high-frequency leakage, but it is fragile and tears if clamped directly. Braid is tough and easy to clamp, but its weave leaves small gaps — which is why combination cable exists. When a datasheet claims 100% coverage, it usually means the foil layer, not the braid.

Termination Methods Ranked by What They Deliver

Every practical termination is a compromise between bond quality and build convenience. Sorted from worst to best in high-frequency terms:

The step from row one to row four is the difference between a cable screened in the catalogue and one screened in the cabinet. Current-carrying capacity, bending radius and gland material all stay the same — only the geometry of the contact changes.

Where a panel is thickness-limited, a nickel-plated brass body with a conductive contact insert, such as the M22 shielded gland, keeps the whole path inside a normal panel thickness.

When Foil Is the Only Screen You Have

Foil-shielded cable is the awkward case, and it turns up constantly in control and instrumentation work because it is inexpensive and terminates easily in a terminal block. The foil is only microns thick: it cannot be clamped or crimped directly, and tears if a cone is screwed down onto it. So the manufacturer supplies a drain wire, and that wire becomes the bond.

Recognise what that is: a single-point bond through one thin conductor, electrically much like a short pigtail. Reasonable for sensor loops, thermocouples and low-speed control in moderate noise; the wrong starting point for a drive-fed motor cable.

If you must use foil cable in a noisy area, keep the exposed drain wire as short as the gland allows and avoid loose loops of screen inside the enclosure — a loop both raises impedance and picks up noise.

Bond One End or Both Ends?

Bond strategy depends on frequency rather than preference.

Bond at both ends when the cable carries a drive output, a servo signal, industrial Ethernet, or anything operating above roughly 1 MHz. At those frequencies the skin effect keeps interference current on the outside of the screen and the signal return on the inside, so the two do not share a path. A screen bonded at one end only has a floating end, and a floating end radiates.

Bond at one end for low-frequency analogue runs — thermocouples, strain gauges, audio — and for cables linking equipment with different earth potentials, such as two buildings with separate earth systems. Here the dominant risk is a circulating current appearing directly as noise on the signal, and the cable is not screened at radio frequencies in this configuration.

If a project has both problems, do not weaken the bond. Bond at both ends and deal with the loop separately, using a common-mode choke or a differential receiver. Our comparison of EMC and standard cable glands sets out what else changes when you move to a screened build.

Sizing: Measure the Cable, Not the Conductor

For larger motor and feeder cables, a longer body is usually the practical choice because it gives the screen more room. An IP68 nickel-plated brass body in the larger metric sizes, such as the M36 shielded gland, accommodates a dressed-back braid without forcing the fit.

Material and Ground Path: Where Good Terminations Fail

A correct termination into a poor ground path is still a failed screen. Three things decide whether the path holds.

• Body material. Nickel-plated brass suits general industrial and indoor use, roughly −40 °C to +120 °C. Stainless steel 304 or 316L is the right answer for washdown, coastal, offshore and chemical exposure, roughly −40 °C to +200 °C; the stainless steel gland range covers these cases.
• What the gland lands on. Powder coating, anodising and heavy oxide layers are insulators. Use an earthing nut or locknut with cutting edges, or mask the hole to bare metal, so the bond reaches the enclosure rather than the paint.
• Corrosion at the contact. A corroded bond becomes a resistor, and a resistive bond behaves like an inductor at high frequency. In wet or saline environments that means stainless steel hardware — a full metal-body stainless steel PG gland keeps the path conductive over time.

Sealing and screening compete for space: the seal compresses on the jacket while the screen compresses onto metal, and neither should be sacrificed for the other. Check that the ingress protection you need is stated for the exact size and cable range you are ordering, because a rating quoted for one size does not transfer to the series.

Common Mismatches That Cost You the Screening

Most of these are caught in the first ten minutes of assembly rather than in a test chamber, which is why the checks belong on the drawing. Our step-by-step walkthrough of installing an EMC cable gland covers the sequence itself, including how to confirm the bond is real before the panel closes.

Conclusion

The choice of shielded cable gland matters less than what happens at the moment the screen meets metal. Match the gland’s contact geometry to the screen construction, keep the transition from screen to enclosure as short and as circumferential as the hardware allows, decide the bonding strategy by frequency rather than habit, and size on the jacket diameter with the screen dressed back.

If you are specifying screened cable entry for a panel, machine or marine installation, send us the cable construction, the outside diameter and the entry thread and we will confirm the gland, the contact element and the earthing hardware to match. Talk to our team with your cable datasheet.

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What is a shielded cable gland?

A cable entry gland whose body and internal clamping components create a low-impedance electrical path between the cable screen and the enclosure. It seals and grips the cable like a standard gland, and additionally terminates the screen circumferentially.

Can I use a standard cable gland on shielded cable?

You can, and in low-noise, low-frequency circuits it often works acceptably. But a standard gland has no component designed to press against the braid, so the screen usually ends up bonded through a drain wire or a twisted pigtail. Above roughly 1 MHz that bond stops carrying the interference current effectively.

Do I need to bond the screen at both ends?

For anything above about 1 MHz — drive outputs, servo signals, industrial Ethernet — yes. For low-frequency analogue signals and runs between equipment with different earth potentials, bond one end to avoid a circulating current. Where both risks exist, bond both ends and treat the loop separately.

How do I terminate a foil shield with a drain wire?

Land the drain wire on an earth terminal or the gland’s earth provision and keep the exposed length as short as the hardware permits. Avoid loose loops inside the enclosure, and fold the foil together with the drain wire where the gland accepts a fold-back.

Are shielded cable glands waterproof?

Many are, and IP68 versions are common because the same sealing components are used. Ingress protection is declared for a specific size and cable range, so check the rating against the exact part number rather than the series as a whole.