Technical Characterisitics

 

Below given are the Technical Characteristics in manufacturing of cables:

  1. Materials used in various types of cables
  2. Insulation Material Properties
  3. Resistance of Insulation Materials
  4. Colour codes for Thermcouple Extension and Compensating Cables
  5. Loop resistance for Thermocouple Conductors
  6. Loop resistance for Copper Conductors

Click on each each of the above characteristic for more details.

1. Materials used in various types of cables

Instrumentation cable construction is of a very complex nature. There is a vast variety of sizes and construction used by various project consultants.

Listed below are various options available within cable constructions, allowing engineers to specify cables that are best suited to the application.

Conductor

Electrolytic grade, annealed plain or tinned copper, either solid or stranded. Thermocouple cables with matched pair of thermocouple alloys.

Insulation
Depending on conductor temperature, flame retardancy, electrical characteristics, compatibility and flexibility various insulating materials such as PVC, Polyethylene, XLPE, Silicon rubber, Mica tape etc.

Identification

Identification either by colour code and /or by no. printed tapes over pairs.

Electrical Screening

Electrical screening is provided over twisted elements and /or total cable to protect fidelity of the signal.


Inner Sheath

Material such as PVC, Polyethylene, FRLS PVC, LSF are used to serve as electrical bedding as well as chemical ingress barriers.

Armour

Galvanized steel wire or strips applied spirally over inner sheath or symmetrical or asymmetrical braid depending on final use of the cable.

Outer Sheath

The choice of sheathing material depends on the application requirements such as temperature, flame retardancy, smoke and acid gas emission limitations (Halogen free), resistance to chemicals and water, flexibility, exposure to UV and hazardous environment, anti-rodent and anti-termite properties. The materials used are PVC and Polyethylene LSF.

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2. Insulation Material Properties

Insulation Material Tensile strength N/MM² Elongation at break % Temperature range C° Dielectric constant
@ 10³Hz
Dissipation factor
@ 10³Hz
Volume resistance Ohm x cm
PVC 15 250 -50
80 to 105
4 to 7 0.02 2X1014
Polyethylene 14 500 -60 to 70 2.27 0.0003 1017
XLPE >15 500 90 250 2.3 0.005


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3. Resistance of Insulation Materials
 

Insulation Material Abrasion Resistance Oil Resistance Solvent Resistance Water Resistance Flame Retardance Radiation Resistance Flexibility
PVC                  
Polyethylene              
XLPE              

POOR
FAIR
GOOD
VERY GOOD





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4. Colour codes for Thermcouple Extension and Compensating Cables
 

Codes/Conductor
combinations
Characteristics of various
standards of Extension
and Compensating Cables

Colour code for Thermocouple Extension 
and Compensating Cables

British Standard
BS 1843

American Standard
ANSI MC 96.1

Indian Standard
IS 8784

International
Electro Technical
Commission

Code Conductor
Combinations

IEC 584-3

+ VE Leg - VE Leg
KX

Nickel
Chromium

Nickel
Aluminium

+/-
2.5°C
+/-
2.2°C
+/-
2.2°C
+/-
2.5°C
VX

Copper

Copper-
Nickel

+/-
2.5°C
- - - - +/-
2.5°C
TX

Copper

Copper-
Nickel

+/-
1.0°C
+/-
1.0°C
+/-
1.0°C
+/-
1.0°C
JX

IRON

Copper-
Nickel

+/-
2.5°C
+/-
2.2°C
+/-
2.2°C
+/-
2.5°C
EX

Nickel
Chromium

Copper-
Nickel

+/-
2.5°C
+/-
1.7°C
+/-
1.7°C
+/-
2.5°C
RX

Copper

Copper-
Alloy

+/-
2.5°C
+/-
1.5°C
+/-
1.5°C
- -
SX

Copper

Copper-
Alloy
+/-
2.5°C
+/-
1.5°C
+/-
1.5°C
+/-
2.5°C
BX

Copper

Copper-
Alloy
- - +/-
0.5°C
+/-
0.5°C
- -


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5. Loop resistance for Thermocouple Conductors

LOOP RESISTANCE (MAX) FOR THERMOCOUPLE CONDUCTORS at 20ºC OHM / Km.

THERMOCOUPLE   TYPE

KX VX TX JX EX RX/SX
1)  20  AWG  Conductor 1910 980 980 1214 2312 280
2)  18  AWG  Conductor 1212 624 624 772 1470 175
3)  16  AWG  Conductor 746 385 385 475 905 110

 
6. Loop resistance for Copper Conductors

LOOP RESISTANCE (MAX) FOR COPPER CONDUCTORS at 20°C OHM / Km.

SIZE IN SQ.MM.

0.5 0.75 18 AWG 1.0 1.5 2.5

Max. resistance
at 20°C

Flexible Copper
Plain Conductors

79.20 50.40 45.00 36.20 25.40 15.30

Max. resistance
at 20°C

Solid Copper
Plain Conductors

72.00 48.00 44.00 35.40 24.20 14.50


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