Twisted Pair vs Coaxial vs BS5308: Which Instrumentation Cable Should You Choose?
- The Direct Answer: No Single “Best” – It Depends on Your Application
People always ask: “What type of instrumentation cable is best?”
The simple answer: There is no single “best” cable – the right choice depends on your signal type, distance, electrical environment, and industry sector.
|
Cable Type |
Best For |
Key Advantage |
Limitation |
|
Twisted Pair |
4-20mA loops, RTDs, thermocouples, RS485/Modbus |
Cancels common-mode noise; cost-effective for analog/digital |
Limited high-frequency performance (>10 MHz) |
|
Coaxial |
High-frequency signals, video, RF, high-speed data (>10 MHz) |
Excellent high-frequency shielding; precise impedance (50/75Ω) |
Higher cost; less flexible; not ideal for low-level analog |
|
BS5308 |
Oil & gas, petrochemical, hazardous areas |
Twisted pair + shielding + mechanical protection + IS rating (blue sheath) |
Higher cost; heavier; overkill for general industrial |
The Bottom Line: Use twisted pair for most process instrumentation (4-20mA, RS485). Use coaxial for high-frequency or video. Use BS5308 when the specification demands it – typically for oil, gas, and petrochemical projects requiring mechanical toughness and hazardous area certification.
At Dingzun Cable, we manufacture all three types. Our engineering team helps you select based on your signal, environment, and industry standard – not just inventory.
- Core Comparison: Twisted Pair vs Coaxial vs BS5308
Understanding the fundamental differences is essential for correct selection.
（Instrumentation cable cross-sections）
Table 1: Twisted Pair vs Coaxial vs BS5308 – Key Parameters
|
Parameter |
Twisted Pair (e.g., 4-20mA, RS485) |
Coaxial (e.g., RG59, RG6) |
BS5308 (Oil & Gas Spec) |
|
Conductor configuration |
Two insulated copper wires twisted together |
Single center conductor + dielectric + braid/foil shield |
Twisted pair(s) + overall shield + mechanical protection |
|
Characteristic impedance |
100Ω, 120Ω (RS485), or 150Ω (analog) |
50Ω (RF), 75Ω (video), 93Ω (data) |
100Ω, 120Ω, or 150Ω (same as twisted pair) |
|
Typical signal type |
4-20mA, thermocouple (mV), RTD (resistance), RS485 (digital) |
Video (CCTV), RF, high-speed data (>10 MHz) |
Same as twisted pair – plus hazardous area (Ex-ia/Ex-ib) |
|
Noise rejection mechanism |
Common-mode rejection via twisting |
Shield reflection and absorption |
Twisting + foil/braid shield + drain wire |
|
Shielding coverage |
70-95% (braid) or 100% (foil) |
100% (foil + braid typically) |
100% foil + braid (composite) typical |
|
Mechanical protection |
Moderate (standard jacket) |
Moderate to high (depending on construction) |
High – often includes GSWA armor, LSZH sheath |
|
Maximum distance (typical) |
1,200m (RS485 at low baud); 500-800m (4-20mA) |
200-500m (video, depends on signal quality) |
Same as twisted pair – plus armor for direct burial |
|
Hazardous area rating |
Available (with blue LSZH sheath) |
Rare |
Common – Ex-ia/Ex-ib with light-blue (RAL 5015) sheath |
|
Relative cost |
1.0× (baseline) |
1.2-1.5× |
1.5-3.0× (depending on armor/certification) |
|
Typical industries |
General industrial, manufacturing, water/wastewater |
Broadcast, security, telecom, high-speed data |
Oil & gas, petrochemical, offshore, mining |
At Dingzun Cable, we offer all three configurations with full customization – conductor gauge, pair count, shielding density, jacket material, armor, and hazardous area certification as required.
- Deep Dive: Twisted Pair – The Workhorse for Analog and RS485
Twisted pair is the most common instrumentation cable for a reason. The twisting mechanism cancels electromagnetic interference.
Table 2: Twisted Pair – Key Specifications and Applications
|
Parameter |
Typical Value |
Why It Matters |
|
Twists per meter |
30-60 twists/m (varies by pair) |
More twists = better common-mode noise rejection |
|
Characteristic impedance |
100Ω, 120Ω, or 150Ω |
Matches termination for RS485 (120Ω) or analog (100-150Ω) |
|
Capacitance (core-core) |
≤60-150 pF/m (PE better than PVC) |
Lower capacitance = longer possible distance |
|
Shielding options |
Unshielded (UTP), foil (ASTP), braid (BSTP), composite (SF/UTP) |
Match to EMI environment – see Table 3 |
|
Max distance (RS485, 9.6 kbps) |
1,200 meters |
Longest among copper-based instrumentation |
|
Max distance (4-20mA) |
500-800 meters (depends on loop resistance) |
Adequate for most plants; longer runs require thicker conductors |
|
Best applications |
4-20mA loops, RTDs, thermocouples, RS485/Modbus, general instrumentation |
Most common choice for process control |
When to Choose Twisted Pair:
|
If You Need... |
Choose Twisted Pair Because... |
|
4-20mA or mV signals |
Low cost, adequate shielding, long distance |
|
RS485/Modbus communication |
Standard impedance (120Ω) available |
|
Thermocouple extension |
Special alloys available (Type J, K, T, etc.) |
|
General plant instrumentation |
Most cost-effective solution |
|
Long runs (up to 1,200m) |
Lower capacitance (PE insulation) enables long distance |
At Dingzun Cable, we manufacture twisted pair instrumentation cables in 1 to 100+ pair configurations, with PE or XLPE insulation for low capacitance, and foil, braid, or composite shielding.
- Deep Dive: Coaxial – High-Frequency and Video Applications
Coaxial cable is designed for high-frequency signals where impedance control is critical.
Table 3: Coaxial Cable – Key Specifications and Applications
|
Parameter |
Typical Value |
Why It Matters |
|
Characteristic impedance |
50Ω (RF), 75Ω (video), 93Ω (data) |
Must match source and load to prevent reflection |
|
Center conductor |
Solid or stranded copper, copper-clad steel (CCS) |
Determines attenuation and flexibility |
|
Dielectric |
Solid or foam PE (lower attenuation) |
Foam PE has lower loss but less crush resistance |
|
Shielding |
Single braid, dual braid, foil + braid, or solid tube |
Dual/composite for high EMI environments |
|
Attenuation (typical RG59) |
16 dB/100m @ 100 MHz |
Higher frequency = higher loss; limits distance |
|
Max distance (analog video) |
200-500m (with proper signal quality) |
Depends on cable quality and signal level |
|
Best applications |
CCTV, RF transmission, high-speed data (>10 MHz), broadcast |
Not for 4-20mA or low-level analog |
When to Choose Coaxial:
|
If You Need... |
Choose Coaxial Because... |
|
Video (CCTV, analog/IP over coax) |
Standard impedance (75Ω) for video |
|
Radio frequency (RF) signals |
Standard impedance (50Ω) for RF |
|
High-frequency data (>10 MHz) |
Superior high-frequency performance vs twisted pair |
|
Long high-frequency runs |
Lower attenuation than twisted pair at high frequencies |
|
Precision impedance control |
Coaxial has tight impedance tolerance (e.g., 75Ω ±3Ω) |
At Dingzun Cable, we manufacture coaxial cables in 50Ω and 75Ω variants, with single, dual, and composite shielding – suitable for CCTV, RF, and high-speed data applications.
- Deep Dive: BS5308 – The Oil & Gas Specification
BS5308 is a British standard specifically for instrumentation cables in the petrochemical industry. It is not a fundamentally different electrical design – it adds mechanical robustness and hazardous area compliance.
Table 4: BS5308 Instrumentation Cable – Key Features
|
Feature |
BS5308 Requirement |
Why It Matters for Oil & Gas |
|
Construction |
Twisted pair(s) + individual screening (foil) + overall screen (braid) |
Maximum EMI protection in high-noise environments (VFDs, pumps, switchgear) |
|
Mechanical protection |
Optional SWA (steel wire armor) or braid |
Resists crushing, impact, rodent damage – required for direct burial, heavy industrial |
|
Sheath color |
Light-blue (RAL 5015) for IS circuits (per IEC 60079-14) |
Immediate identification of intrinsically safe circuits |
|
IS rating |
Ex-ia (Zone 0/1) or Ex-ib (Zone 1) common |
Safe for hazardous areas with flammable gases/vapors |
|
Flame retardancy |
IEC 60332-1 or IEC 60332-3 (bundled) |
Prevents fire spread in cable trays and risers |
|
LSZH |
Low smoke zero halogen optional (BS5308 Part 2 Type 2) |
Required for enclosed spaces (platforms, control rooms, tunnels) |
|
Typical industries |
Oil & gas (onshore/offshore), petrochemical, refining, chemical plants |
Specification often mandated by engineering contractors (e.g., Shell, BP, Total) |
BS5308 Part Classification:
|
Part |
Description |
Typical Use |
|
BS5308 Part 1 |
PVC insulated, PVC sheathed |
General purpose (non-LSZH) |
|
BS5308 Part 2 |
PVC insulated, LSZH sheathed |
Fire-safe, low smoke (offshore, enclosed areas) |
|
Type 1 |
Individual and overall screening |
Standard EMI protection |
|
Type 2 |
Overall screening only (no individual pair screen) |
Lower cost, less demanding EMI |
When to Choose BS5308:
|
If You Need... |
Choose BS5308 Because... |
|
Oil & gas project specification |
Often mandated by engineering spec (client requirement) |
|
Hazardous area (Zone 1/2) IS circuits |
Light-blue sheath, Ex-ia/Ex-ib rating, documented Cc/Lc parameters |
|
Direct burial or heavy industrial |
SWA armor available |
|
Fire safety (low smoke, zero halogen) |
Part 2 LSZH construction |
|
Refinery, chemical plant, offshore platform |
Standard in these industries – known, accepted, trusted |
At Dingzun Cable, we manufacture BS5308 compliant instrumentation cables (Part 1 and Part 2, Type 1 and Type 2) with full certification – including SWA armor, LSZH sheathing, light-blue IS identification, and documented entity parameters for hazardous area compliance.
- Selection Flowchart: Which Cable Should You Choose?
Use this decision framework to select the right cable type.
Table 5: Instrumentation Cable Selection Decision Flow
|
Question |
Yes → |
No → |
|
Is the signal high-frequency (>10 MHz) or video? |
Coaxial (50Ω or 75Ω) |
Continue |
|
Is the signal 4-20mA, thermocouple, RTD, or RS485 (≤10 MHz)? |
Continue |
Reconsider signal type |
|
Is the project in oil & gas, petrochemical, or offshore? |
BS5308 (or client may specify another standard like IEC 60092) |
Continue |
|
Does the specification require BS5308, SWA armor, or hazardous area (Ex-ia/Ex-ib)? |
BS5308 |
Continue |
|
Is cost the primary driver and environment is general industrial? |
Twisted pair (unshielded or foil/braid as needed) |
Continue |
|
Is the environment electrically noisy (VFDs, motors, welders)? |
Twisted pair with composite shield (foil + braid) |
Twisted pair with basic shield (foil or braid) |
(Instrumentation cable selection for a customized flowchart for your project)
Practical Examples:
|
Application |
Recommended Cable |
Why |
|
4-20mA pressure transmitter in general plant |
Twisted pair (foil shield) |
Cost-effective; adequate for moderate EMI |
|
RS485 network in VFD-heavy factory |
Twisted pair (composite shield + 120Ω impedance) |
Protects against broadband EMI |
|
CCTV camera in industrial plant |
Coaxial (75Ω, dual shield) |
Standard for analog video; good shielding |
|
Instrumentation in oil refinery (Zone 1) |
BS5308 Part 2 Type 1 (LSZH, Ex-ib) |
Meets spec; IS rating; fire safety |
|
Direct burial IS cable in petrochemical plant |
BS5308 with SWA armor + light-blue LSZH |
Mechanical protection + hazardous area compliance |
|
High-speed data acquisition (>10 MHz) |
Coaxial or shielded twisted pair (depending on interface) |
Match to transceiver requirement |
At Dingzun Cable, we provide a free selection consultation with a flowchart customized to your project requirements. Contact our engineering team with your signal type, environment, and any industry standards.
- Quick Comparison Summary
|
Selection Factor |
Twisted Pair |
Coaxial |
BS5308 |
|
Best for signal type |
4-20mA, mV, RTD, RS485 |
Video, RF, high-speed data |
Same as twisted pair + hazardous area |
|
Typical impedance |
100-150Ω |
50Ω or 75Ω |
100-150Ω (same as twisted pair) |
|
Max distance |
1,200m (RS485 low baud) |
200-500m (video) |
Same as twisted pair (plus armor for burial) |
|
EMI protection |
Good to excellent (depending on shield) |
Excellent (high-frequency) |
Excellent (composite shield typical) |
|
Mechanical toughness |
Moderate |
Moderate to high |
High (SWA armor optional) |
|
Hazardous area (IS) rating |
Available (blue sheath) |
Rare |
Common (light-blue, Ex-ia/Ex-ib) |
|
Relative cost |
Low to moderate |
Moderate |
Moderate to high |
|
Primary industry |
General industrial, manufacturing |
Broadcast, security, high-speed data |
Oil & gas, petrochemical, offshore |
At Dingzun Cable, we manufacture all three types with full customization – including BS5308 certification, SWA armor, LSZH sheathing, and hazardous area (Ex-ia/Ex-ib) ratings. We help you select based on your signal, environment, and industry standard – not just what is in stock.
About Dingzun Cable: Your Instrumentation Cable Engineering Partner
With 20+ years of specialized manufacturing experience, Dingzun Cable is a trusted partner for global industrial projects, oil & gas facilities, and general manufacturing plants requiring high-quality instrumentation cables – including twisted pair, coaxial, and BS5308 certified types. We combine deep signal integrity expertise with extreme customizability to deliver cables that match your exact application.
(Dingzun Cable instrumentation cables)
Our Instrumentation Cable Capabilities:
|
Capability |
Dingzun Specification |
|
Cable types |
Twisted pair (UTP/STP), Coaxial (50Ω/75Ω), BS5308 Part 1 & 2 (Type 1 & 2) |
|
Twisted pair pairs |
1 to 100+ pairs |
|
Conductor gauge |
18 AWG to 24 AWG |
|
Conductor material |
Bare copper, Tinned copper |
|
Insulation |
PE (low capacitance), PVC, XLPE |
|
Shielding |
Foil (100%), braid (70-95%), composite (foil+braid) |
|
BS5308 features |
Individual + overall screen, SWA armor, LSZH sheath, light-blue (RAL 5015) |
|
Hazardous area |
Ex-ia (Zone 0/1), Ex-ib (Zone 1) – documented Cc/Lc parameters |
|
Impedance (twisted pair) |
100Ω, 120Ω ±5Ω (RS485), 150Ω |
|
Impedance (coaxial) |
50Ω ±2Ω, 75Ω ±3Ω |
|
Certifications |
ISO 9001:2015, UL, CE, RoHS, REACH, BS5308 compliance |
|
Testing |
100% electrical testing on every reel |
Why Dingzun Cable for Your Instrumentation Cable Needs:
- Complete range – Twisted pair, coaxial, and BS5308 – all under one roof
- BS5308 certified – Full compliance with Parts 1 & 2, Types 1 & 2, SWA armor, LSZH
- Expert engineering team – Free selection consultation based on signal type, environment, and spec
- Extreme customizability – Pairs, gauge, shielding, jacket, armor – fully tailored
- Direct professional communication – Fast quotes, technical datasheets, global shipping
- Full documentation – Test reports, certificates of compliance, entity parameters for IS
Need help selecting between twisted pair, coaxial, or BS5308 for your project?
[Contact our technical team today for a free consultation and custom quote].