OS-TP-300/500V
Overall Screened Twisted Pair Cable for EMC-Critical Panels
Foil for coverage, braid for the return path — the construction panels need next to drives.
Twisting and screening solve two different halves of the same problem. Twisting makes an external magnetic field induce equal and opposite voltages in the two conductors, so a differential receiver cancels them; screening stops an external electric field reaching the conductors at all. A pair that is only twisted still picks up capacitively coupled noise, and a pair that is only screened has no defence against a magnetic field crossing the loop area between the conductors.
This construction does both, and then adds a second screen layer: aluminium foil for 100 % coverage, with a tinned copper braid over it to carry the interference current to earth. That combination is what belongs in a panel where a 100 mV analogue signal, a 4–20 mA loop and a contactor coil all live within a few hundred millimetres of each other, and where a single-layer screen will not hold the error inside tolerance.
Specification
| Item | Value |
|---|---|
| Rated voltage U0/U | 300/500 V |
| Conductor | Class 5 flexible plain annealed copper, IEC 60228 |
| Number of pairs | 1 – 24 |
| Cross-section range | 0.5 – 2.5 mm² |
| Insulation | Polyethylene or PVC, to the capacitance requirement |
| Pair twisting | Lay length 40–70 mm, varied between adjacent pairs |
| Pair screen | Optional aluminium foil per pair with drain wire (PiMF variant) |
| Overall screen | Aluminium foil 100 % coverage plus tinned copper braid ≥ 85 % coverage, with drain wire |
| Sheath | PVC grey or black; LSZH and blue Ex i variants available |
| Mutual capacitance at 1 kHz | ≤ 60–85 pF/m |
| Test voltage | 2 kV rms core to core, 1 kV rms core to screen, 5 min |
| Minimum bending radius | 10 × cable overall diameter |
Layer-by-layer construction
Listed from the conductor outward. Read this alongside the specification table — the two together tell you whether the cable will survive its installation method.
- 1. ConductorBunched fine-wire plain annealed copper, Class 5 to IEC 60228
- 2. InsulationPolyethylene or PVC extruded at 0.5–0.7 mm wall, colour coded per conductor
- 3. Pair twistingTwo cores twisted at a 40–70 mm lay length, varied between adjacent pairs to limit crosstalk accumulation
- 4. Foil screenAluminium-laminated polyester foil applied with overlap over the bundle, 100 % coverage, with a tinned drain wire
- 5. Braid screenTinned copper wire braid at ≥ 85 % coverage over the foil, carrying interference current to earth
- 6. SheathPVC grey or black, 1.2–1.8 mm nominal; LSZH and light blue Ex i variants available
Reference dimensions and weights
| Pairs × cross-section (mm²) | Conductor structure (No./mm) | Insulation thickness (mm) | Braid wire diameter (mm) | Pair lay length (mm) | Approx. overall diameter (mm) | Approx. weight (kg/km) | Max. DC resistance at 20 °C (Ω/km) | Mutual capacitance at 1 kHz (pF/m) |
|---|---|---|---|---|---|---|---|---|
| 4×2×0.5 | 16/0.20 | 0.5 | 0.15 | 45 | 12.2 | 240 | 39.0 | ≤ 60 |
| 4×2×0.75 | 24/0.20 | 0.5 | 0.15 | 50 | 13.6 | 300 | 26.0 | ≤ 65 |
| 4×2×1.0 | 32/0.20 | 0.6 | 0.15 | 55 | 15.0 | 370 | 19.5 | ≤ 70 |
| 4×2×1.5 | 30/0.25 | 0.6 | 0.15 | 60 | 16.6 | 470 | 13.3 | ≤ 75 |
| 4×2×2.5 | 50/0.25 | 0.7 | 0.20 | 70 | 19.6 | 660 | 7.98 | ≤ 85 |
Reference figures for preliminary sizing and drum planning. Overall diameter and weight vary with strand construction and sheath thickness tolerance; certified drawings are issued with each quotation.
Engineering characteristics
- Two-layer screen: 100 % foil coverage for electric fields plus a ≥ 85 % tinned braid for the current path
- Twisted pairs at 40–70 mm lay length, varied between adjacent pairs so crosstalk does not accumulate
- Polyethylene option holds mutual capacitance at ≤ 60–85 pF/m for long analogue runs
- 300/500 V rating, 2 kV rms core to core and 1 kV rms core to screen
- Class 5 conductors give a smaller bending radius than a Class 2 equivalent inside a crowded panel
- Foil plus braid keeps screen transfer impedance low from power frequency through to tens of megahertz
- Supplied in 1 to 24 pairs with numbered tape or printed identification above 10 pairs
Typical applications
- Panels where analogue inputs share a cable route with contactors and drive output leads
- PLC and DCS analogue input homeruns in EMC-hostile plant areas
- Signal wiring downstream of a variable frequency drive or a soft starter
- Test and measurement looms where millivolt signals must stay inside tolerance
- Control room marshalling with mixed signal types in one sheath
Ordering options
- PiMF variant with a foil screen on each pair in addition to the overall foil and braid
- Polyethylene or PVC insulation, chosen on the capacitance requirement
- LSZH sheath to IEC 60754-1 and IEC 61034-2
- Light blue sheath with documented capacitance and inductance for Ex i circuits
- Armoured version with steel wire braid for outdoor and inter-building runs
Standards manufactured to
- GB/T 9330 (construction and test practice)
- IEC 60228 (conductor)
- IEC 60332-1-2 (flame propagation)
- IEC 61000-4-6 (immunity practice for screened signal cable)
- IEC 60079-14 (intrinsically safe installation practice)
- RoHS and REACH compliant compounds
Manufactured to other standards on request. Send the standard number with your RFQ and we will quote against it rather than against a near-equivalent.
Price and availability for Overall Screened Twisted Pair Cable
Include cross-section, core count, voltage grade, route length and installation method — those five determine price more than anything else on the page.
- Engineer-reviewed before pricing
- Reference drawings issued with the quotation
- Free sample up to free sample up to 5 m
Overall Screened Twisted Pair Cable — frequently asked questions
Why both a foil and a braid?
The foil gives 100 % coverage, so no field leaks through an aperture, but it is thin and has a relatively high resistance along its length. The braid adds a low-resistance path that carries the interference current to earth. Neither layer alone covers both frequency ranges well.
Does twisting alone solve the noise problem?
No. Twisting cancels magnetically induced voltage, because the field induces equal and opposite voltages in the two conductors and the differential receiver rejects them. It does nothing about capacitively coupled current, which is what the screen addresses.
Should the overall screen be earthed at both ends?
For a panel in an EMC-hostile area, yes, through a 360° gland or clamp at both ends, so the interference current has a path that does not pass through the signal conductors. For a low-frequency analogue loop on a single earth reference, one end is enough and avoids ground-loop current.
Can I run 24 V DC switching and a 4–20 mA loop in the same screened cable?
Only with the PiMF variant, where each pair has its own foil screen. The overall screen stops interference entering the cable but not interference generated between pairs inside it; an inductive load switched in one pair will still inject a spike into the pair next door.
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