What are shielded armored instrument cables?
Shielded and armored instrument cables are used to transmit low-voltage analog signals (e.g., 4-20mA) or digital signals. Their core feature is the addition of a metallic armor layer (such as steel tape or steel wire armor) to the basic shielded instrument cable, providing extra mechanical protection.
Shielding: Shielded with aluminum foil, copper wire braid, or composite tape to resist electromagnetic interference (EMI) and ensure signal purity.
Armored: Steel tape armor (STA) or steel wire armor (SWA) to protect against external mechanical damage, such as crushing, rodent bites, or construction damage.
Common standards: BS 5308, IEC 60332, UL 2250, and GB/T 9330, etc.
Why is dual protection—shielding and armoring—needed?
In many industrial control environments, cables face complex challenges:
Environmental challenges: Cables may be buried directly underground or laid in trenches filled with machine oil.
Interference challenges: Instrument cables are often laid parallel to high-power power cables. Without shielding, frequency converter harmonics from the motor can interfere with instrument signals, causing fluctuations in the DCS system’s displayed data.
Therefore, shielded and armored instrument cables exist to ensure signal integrity in harsh industrial environments.
Structure of Shielded Armored Instrument Cables
Shielded armored instrument cables employ a multi-layer design, comprising, from the inside out:
Conductor: Multi-strand tinned copper wire (0.5-1.5mm²), flexible and corrosion-resistant.
Insulation: XLPE, PVC, or LSZH (low smoke halogen-free).
Twisted Pairs + Individual Shielding: Each pair of core wires is twisted and individually shielded (aluminum-plastic composite tape + drainage line).
Overall Shielding: Integral copper wire braid or aluminum foil shielding.
Inner Sheath: PVC or LSZH filler layer.
Armor Layer: Steel tape armor (double steel tape wrapping) or steel wire armor (high tensile strength).
Outer Sheath: Oil-resistant, weather-resistant PVC or special materials.
Comparison of different instrument cables
| characteristic | ordinary cable | Only Armored | Only shielded. | Shielded Armored �� |
|---|---|---|---|---|
| Anti-interference | Bad | Bad (the armor attracts magnets). | good | Excellent |
| Anti-rollover | weak | powerful | Weak (flattened easily when pressed) | Extremely strong |
| Rat bite prevention | weak | powerful | weak | powerful |
| price | $ | $$ | $$ | $$$ |
| in conclusion | Indoor use | Power transmission | Clean environment | For use in harsh environments |
Common Models
Common Models in China
| model | Detailed Explanation of Meaning | Main features and application scenarios |
|---|---|---|
| DJYPVP22 | Copper core PE insulation, twisted pair shielding (copper strip) + main shielding (copper strip), PVC inner/outer sheath, steel strip armor | Split-screen + main-screen configuration offers the strongest anti-interference capability, ideal for direct burial or high-interference environments. |
| DJYVP22 | Copper core PE insulation, main shield (copper wire braid), PVC sheath, steel tape armor | Overall shielding, general-purpose, with good mechanical protection. |
| DJYPV22 | Copper core PE insulation, twisted pair shielding (copper strip), PVC sheath, steel strip armor | Partial shielding, multiple pairs of independent signal transmissions |
| DJYPVP32 | Same as DJYPVP22, but with steel wire armor (32). | Higher tensile strength, suitable for tensile or suspended installation. |
| ZR-DJYPVP22 | Flame-retardant DJYPVP22 | Locations with high fire safety requirements, such as chemical plants |
| IA-DJYPVP22 | Intrinsically safe DJYPVP22 | Explosion-proof areas (such as oil platforms) |
| KYJVP2-22 | Copper core XLPE insulation, copper tape shielding, PVC sheath, steel tape armor | Higher temperature resistance (90℃), high temperature environment |
Other common models
| model | Detailed Explanation of Meaning | Main features and application scenarios |
|---|---|---|
| RE-Y(St)Y-SWA-PVC | Overall shielding, steel wire armor, PVC sheath | Collective shielding, general mechanical protection |
| RE-Y(St)Y PiMF-SWA-PVC | Individual shielding per pair + overall shielding, steel wire armor, PVC sheath. | Highest resistance to interference, offshore/oil platforms |
| PE-IS-OS-SWA-PVC | PE insulation, independent + overall shielding, steel wire armor, PVC sheath | Intrinsically safe types are common, with a blue outer sheath. |
| XLPE-IS-OS-SWA-LSZH | XLPE insulation, independent + overall shielding, steel wire armor, low smoke halogen-free sheath | High temperature + fire prevention, nuclear power/ship |
FAQ
Q: Can shielded armored cables directly replace ordinary KVVP cables?
A: Upgrading is only recommended when there is a risk of mechanical damage in the field (e.g., direct burial, heavy-load areas). If only interference suppression is required, ordinary KVVP is more economical. Do not replace in reverse: replacing KVVP with KVV22 (unshielded armored) will cause signal distortion!
Q: Should the shielding layer grounding terminal be “field end” or “control cabinet end”?
A: The unified principle is to connect it to the end with the weakest interference source. Usually, there are few interference sources inside the control cabinet, so the shielding layer is grounded at a single point on the control cabinet end.
Q: How to quickly verify the shielding effect?
A: Simple method: Use a multimeter to test the continuity of the shielding layer; Professional method: Request the supplier to provide a “transfer impedance” test report.