THERMOCOUPLE CABLES
THERMOELECTRICITY When a metallic conductor is exposed to a difference of temperature between the two extremities, an electromotive force (emf) is generated by the temperature gradient, which causes a redistribution of the electrons through the conductor. The EMF value depends on the material and the temperature gradient. Let s consider two materials, generically denominated A and B, exposed to the same difference of temperature between their extremities. In each one an electromotive force will result. The EMF value depends on the type of material and the temperature gradient. In case of a homogeneous material the EMF value depends solely on the difference of temperature between the extremities. The phenomenon described above is fundamental to understand the thermoelectricity and its applications to measurement of temperature it s called See beck Effect, which is what creates the sensor known as thermocouple or thermoelectric couple. Elements A and B that make up a thermocouple are denominated Thermo elements. In the configuration of a thermocouple, the extremity at which the thermo elements are joined is called Measuring (or hot) Junction. If the temperature of the Reference (or cold) Junction, the other extremity, is fixed at 0 C, then the EMF value will depend solely on the temperature of the Measuring (or hot) Junction. Extension and Compensating cables Extension and compensating cables shall have temperature-emf characteristics similar to the thermocouple with which they should be connected to transfer signals from the Measuring (or hot) Junction to the Reference (or cold) Junction. Extension cables comprise conductors with the same nominal composition as the corresponding thermocouple; compensating cables comprise conductors with different nominal composition but same temperature EMF characteristics as the corresponding thermocouple.
Table 1 : Table 2 : Loop Resistance at 20 C (nominal value in Ω/km) Conductor material Conductor Size Thermocouple IEC 60584 0.5 mm 2 0.8 mm 2 1.0 mm 2 1.3 mm 2 1.5 mm 2 0.8 mm Ø 1.02 mm Ø 1.13 mm Ø 1.29 mm Ø 1.38 mm Ø Solid Ω/km J JX 1257 769 628 483 418 T TX 1044 639 522 402 348 E EX 2493 155 1246 958 831 K KX 2039 1248 1020 785 680 K KCB 1044 639 522 402 348 K KCA 1298 794 649 499 433
In most cases thermocouples are connected to other processing instruments by connecting cables. Connecting cables are divided into compensating cables and extension cables. These can again be divided into solid and stranded conductors. Extension cables are connecting cables with conductors made of thermocouple material, i.e. of the same material as the thermocouple itself. Extension cables therefore are subject to the same accuracy limits as the thermocouples. Extension cables are marked with an X behind the identification letter for the thermocouple. For example, KX means that the cable is an extension cable / insulated thermocouple wire for the thermocouple type K (NiCr-Ni). Compensation cables are connecting cables with conductors made of materials which only in a limited temperature range have the same thermoelectric properties as the thermocouple itself. Compensating cables are marked with a C behind the identification letter for the thermocouple. For example, KC means that the cable is a compensating cable for the thermocouple type K. The insulation of the conductors as well as of the sheaths can be made of a variety of materials. The following criteria must be taken into consideration when selecting the appropriate material: chemical and mechanical resistance against the ambient conditions, temperature range, insulation resistance, flexibility, outside diameter, screening etc. Apart from that there is a large number of cable types available as compensating cables or extension cables as well as those with more than two inner conductors. Many special designs are available upon request, most of them on a short term basis.
Common Types Extension and Compensating Cable Solid conductor pairs, individual and/or overall static screen. Common Types Halogen-free, flame retardant types Fire resistance, Flame retardant types 500V PVC or PVCw or PE or XLPE (70 C) (105 C) (70 C) (90 C) Insulated/PVC-sheathed PE or XLPE (70 C) (90 C) Insulated/LSOH-sheathed Non- Non-
Common Types Single & Multipair, Individual and/or Collective screen, PVC-sheath» Non-»» With or without chemical protection, armoured Technical Data Type of insulation/sheath Type of cabling elements No.of cabling elements Conductor material Conductor sizes 1. Non- types» Laying» Bending radius 2. types» Laying» Bending radius PVC/PVC PVCw/PVCw PE/PVC XLPE/PVC Pair, Pair in Metal Foil 1, 2, 4, 5, 6, 8, 10, 12, 16, 20, 24 Extension or compensating material acc. to IEC 60584-3 / see Table 1, page ii 0.8 mm, 1.02 mm, 1.13 mm, 1.29 mm, 1.38 mm SC-01 SC-02 SC-03 SC-04 Recommended for indoor and outdoor installation, on racks, trays, in conduits, in dry and wet locations 7.5 x cable Ø SC-05 SC-06 SC-07 SC-08 Recommended for indoor and outdoor installation, on racks, trays, in conduits, in dry and wet locations, for direct burial 10 x cable Ø 3. Temperature range» During operation» During installation - 30 C up to 70 C - 5 C up to 50 C - 30 C up to 105 C - 5 C up to 50 C - 30 C up to 70 C - 5 C up to 50 C - 30 C up to 90 C - 5 C up to 50 C 4. Reaction to fire» Flame propagation a) Test on single cable b) Test on bunched cables Application IEC 60332-1 IEC 60332-3 For transmission of thermoelectric voltage from measuring junction to reference junction; allowed for use in zone 1 and zone 2, group II (IEC 60079-14)
Common Types Single & Multipair, Individual and/or Collective screen, PVC-sheath Non- With or without chemical protec on, armoured Construction Product Type Non- Types Types Conductor Extension or compensating material acc. to IEC 60584-3» cross-section (mm 2 )» conductor design (mm) 0.5 1 x 0.8 0.75 1 x 1.02 1.0 1 x 1.13 1.3 1 x 1.29 1.5 1 x 1.38 Insulation materials Cabling element 1)» without ind. Screen» with ind. Screen Individual screen Wrapping Overall screen Cross linked Polyethylene (XLPE) or Polyethylene (PE) or Polyvinylchloride (PVC) or Polyvinylchloride heat resistant PVCw Pair Pair in Metal Foil Aluminium/Plastic-tape over solid tinned copper drain wire, 0.6 mm plastic tape under and above screen at least one plastic tape above cable core Aluminium/Plastic-tape over solid tinned copper drain wire 0.5 mm 2 / 20 x 0.18 mm Inner sheath -- PVC and PVCw resp., black Armouring -- Galvanised steel wire armouring; wire Ø depending on cable- Ø under armouring, at least 0.9 mm Outer sheath PVC and PVCw resp., Colour see Table 1, page ii Marking Length e.g:. EXTENSION OR COMPENSATING CABLE. STANDARD. RATED VOLTAGE. RP 2). LENGTH MARKING 1000 meter/drum 1) Colour code of cabling elements : see Table 1 2) RP = Reduced flame propagation
Common Types Single & Multipair, Individual and/or Collective screen, PVC-sheath» Non-»» With or without chemical protection, armoured Electrical Data at 20 C Properties Character Unit Conductor sizes nom. mm 2 0.5 0.75 1.0 1.3 1.5 Conductor resistance (Loop) max. Ω/km see Table 2, page ii Insulation resistance PVC / PVCw - insula on min. MΩ.km PE/ XLPE - insula on min. MΩ.km Mutual capacitance PVC / PVCw - insula on Pair 1), 2) max. nf/km Pair in Metal Foil max. nf/km 100 5000 150 190 160 200 PE / XLPE - insula on Pair 1), 2) max. nf/km Pair in Metal Foil max. nf/km 75 85 115 115 Test Voltage Core/Core (U rms ) Core/Screen (U rms ) V V 1500 1500 Operating voltage (U rms ) max. V 300 1) Values for cables with 1 element correspond to those for Pair in Metal Foil 2) Values for cables with 2 up to 4 elements + 20%
Halogen-free, flame retardant types Extension and Compensating Cable Solid conductor pairs, individual and/or overall static screen. Common Types Halogen-free, flame retardant types Fire resistance, Flame retardant types 500V PVC or PVCw or PE or XLPE (70 C) (105 C) (70 C) (90 C) Insulated/PVC-sheathed PE or XLPE (70 C) (90 C) Insulated/LSOH-sheathed Non- Non-
Halogen-free, flame retardant Types Single & Multipair, Individual and/or Collective screen, PVC-sheath» Non-» Technical Data Type of insulation/sheath PE/LSOH XLPE/LSOH Type of cabling elements No.of cabling elements Conductor material Conductor sizes 1. Non- types» Laying» Bending radius 2. types» Laying» Bending radius 3. Temperature range» During operation» During installation 4. Reaction to fire» Flame propagation a) Test on single cable b) Test on bunched cables» Test on gases evolved during combustion: a) amount of halogen acid gas b) degree of acidity of gases Measurement of smoke density Application Pair, Pair in Metal Foil 1, 2, 4, 5, 6, 8, 10, 12, 16, 20, 24 Extension or compensating material acc. to IEC 60584-3 / see Table 1, page ii 0.5 mm 2, 0.75 mm 2, 1.0 mm 2, 1.3 mm 2, 1.5 mm 2 SC/LSOH-01 SC/LSOH-02 Recommended for indoor and outdoor installation, on racks, trays, in conduits, in dry and wet locations 7.5 x cable Ø SC/LSOH-03 SC/LSOH-04 Recommended for indoor and outdoor installation, on racks, trays, in conduits, in dry and wet locations, for direct burial 10 x cable Ø - 30 C up to 70 C - 30 C up to 70 C - 5 C up to 50 C - 5 C up to 50 C IEC 60332-1 IEC 60332-3 IEC 60754-1 (0%) IEC 60754-2 (ph > 4.3, c < 10µS/mm) IEC 61304-2 (Light transmission > 60%) For transmission of thermoelectric voltage from measuring junction to reference junction; allowed for use in zone 1 and zone 2, group II, classified areas (IEC 60079-14)
Halogen-free, flame retardant Types Single & Multipair, Individual and/or Collective screen, PVC-sheath Non- Construction Product Type Non- Types Types Conductor» cross-section (mm 2 )» conductor design (mm) Insulation materials Cabling element 1)» without ind. Screen» with ind. Screen Individual screen Wrapping Overall screen Extension or compensating material acc. to IEC 60584-3 0.5 0.75 1.0 1.3 1.5 1 x 0.8 1 x 1.02 1 x 1.13 1 x 1.29 1 x 1.38 Polyethylene (PE) or Cross linked Polyethylene (XLPE) or Pair Pair in Metal Foil Aluminium/Plastic-tape over solid tinned copper drain wire, 0.6 mm plastic tape under and above screen at least one plastic tape above cable core Aluminium/Plastic-tape over solid tinned copper drain wire 0.5 mm 2 / 20 x 0.18 mm Inner sheath -- LSOH, black Armouring -- Galvanised steel wire armouring; wire Ø depending on cable- Ø under armouring, at least 0.9 mm Outer sheath Colour Marking Length LSOH black or blue for intrinsically safe systems e.g:. EXTENSION OR COMPENSATING CABLE. STANDARD. RATED VOLTAGE. LSOH. LENGTH MARKING 1000 meter/drum 1) Colour code of cabling elements : see Appendix 1, Table 1
» Non-» Electrical Data at 20 C Properties Character Unit Conductor sizes nom. mm 2 0.5 0.75 1.0 1.3 1.5 Conductor resistance (Loop) max. Ω/km Insulation resistance PE/ XLPE - insula on min. MΩ.km Inductance max. mh/km Mutual capacitance PE / XLPE - insula on Pair 1), 2) max. nf/km Pair in Metal Foil max. nf/km see Table 2, page ii 5000 1 75 85 115 115 Test Voltage Core/Core (U rms ) Core/Screen (U rms ) V V 1500 1500 Operating voltage (U rms ) max. V 300 1) Values for cables with 1 element correspond to those for Pair in Metal Foil 2) Values for cables with 2 up to 4 elements + 20%