TC-KX/KCA

KX and KCA Alloy Conductor Cable — Extension versus Compensating Grades

Same-alloy KX or substitute-alloy KCA, with the tolerance range stated on the datasheet.

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Lead time15–25 working days
Minimum500 m per size
SampleFree up to 5 m

Illustrative cross section. Construction layers listed below.

The letter after K is the whole specification. X means extension: the conductors are drawn from the same nickel-chromium and nickel-silicon alloys as the Type K thermocouple, so the cable continues the sensor's own EMF characteristic. CA means compensating: the positive leg is copper and the negative leg a copper-nickel alloy whose thermoelectric behaviour reproduces the Type K curve over a limited temperature span.

Choosing between them is a trade between accuracy and cost. KX holds Class 1 tolerance of ±1.5 °C and tolerates a hotter route; KCA costs less, has roughly a tenth of the loop resistance, and is entirely adequate where the cable stays between 0 °C and 150 °C. Voltcore states the valid range for each grade on the datasheet, because that range — not the tolerance figure alone — is what determines whether the cable is suitable for a given route.

Specification

KX and KCA grades — Technical Specification
Item	Value
Thermocouple type	Type K
KX grade conductors	Nickel-chromium positive, nickel-silicon negative — same nominal alloys as the sensor
KCA grade conductors	Copper positive, copper-nickel negative — substitute alloys matching Type K EMF over a limited range
Tolerance class	Class 1 ±1.5 °C; Class 2 ±2.5 °C, to IEC 60584-3
Valid tolerance range	KX: −20 °C to +200 °C; KCA: 0 °C to +150 °C
Cross-section range	0.5 – 2.5 mm²
Insulation	PVC rated 105 °C; PTFE, FEP and LSZH available
Screen	Aluminium foil with tinned drain wire, or copper wire braid
Sheath	PVC green to IEC 60584-3; ANSI yellow available
Construction	1 pair as standard, up to 12 pairs for multi-point monitoring
Test voltage	1 kV rms core to core, 500 V 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. ConductorKX: nickel-chromium positive and nickel-silicon negative. KCA: copper positive and copper-nickel negative
2. InsulationPVC rated 105 °C, 0.5–0.7 mm wall, coloured to the IEC or ANSI code for the grade
3. Pair twistingPositive and negative conductors twisted at a 35–60 mm lay length
4. Binder tapePolyester tape over the pair where a screen is specified
5. ScreenAluminium foil with tinned drain wire, or tinned copper wire braid at ≥ 85 % coverage
6. SheathPVC green to IEC 60584-3, yellow to ANSI practice, or light blue for Ex i circuits

Reference dimensions and weights

KX and KCA cable — 1 pair, loop resistance comparison (reference figures)
Nominal cross-section (mm²)	Conductor structure (No./mm)	Insulation thickness (mm)	Approx. overall diameter (mm)	Approx. weight (kg/km)	KX loop resistance (Ω/km)	KCA loop resistance (Ω/km)
0.5	7/0.30	0.5	3.6	34	1 980	250
0.75	7/0.37	0.5	4.0	46	1 320	167
1.0	7/0.43	0.6	4.6	60	990	125
1.5	7/0.52	0.6	5.2	82	660	83
2.5	7/0.68	0.7	6.2	126	396	50

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

KX continues the sensor's own EMF curve because the conductors are the same nominal alloys
KCA substitutes copper and copper-nickel legs, giving roughly a tenth of the KX loop resistance
Class 1 tolerance of ±1.5 °C or Class 2 of ±2.5 °C, stated against a defined temperature range
Valid range of −20 °C to +200 °C for KX and 0 °C to +150 °C for KCA, published on every datasheet
Screened and unscreened versions, because the signal is only about 4 mV at 100 °C
Both grades identified to IEC 60584-3, with ANSI yellow coding available
Supplied in 1 to 12 pairs for multi-point furnace and kiln monitoring

Typical applications

KX: furnace, kiln and oven routes where the cable passes through warm zones
KCA: control room and marshalling runs where the route stays cool and cost matters
Multi-point temperature monitoring on heat treatment and annealing lines
Plastics machinery barrel and die zones with many sensors on one cable
Replacement of existing Type K circuits where the grade must match the original

Ordering options

KX or KCA grade, Class 1 or Class 2 tolerance
PTFE, FEP or LSZH insulation where the route is hot or the specification requires it
Foil screen with drain wire, or copper wire braid screen
Up to 12 pairs with numbered pair identification
IEC green, ANSI yellow or light blue Ex i sheath colour

Standards manufactured to

IEC 60584-3 (extension and compensating cables, tolerances, colour coding)
ANSI/ASTM E230 (temperature-EMF reference tables)
IEC 60228 (conductor construction)
IEC 60332-1-2 (flame propagation)
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 KX and KCA Alloy Conductor Compensating 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

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KX and KCA Alloy Conductor Compensating Cable — frequently asked questions

When should I pay for KX instead of KCA?

When the cable route leaves the 0 °C to 150 °C window, or when the tolerance budget is tight. Outside its stated range a KCA cable is not simply less accurate, it is wrong by an unpredictable amount, because the substitute alloy's EMF curve diverges from Type K.

Why is the KCA loop resistance so much lower?

One leg is copper. Nickel-chromium has a resistivity roughly forty times that of copper, so a KX pair at 0.5 mm² measures about 1 980 Ω/km against roughly 250 Ω/km for KCA. Neither figure affects accuracy, since a thermocouple input draws almost no current.

Can I join KX and KCA in the same circuit?

No. Every junction of dissimilar metals is a thermocouple in its own right, so mixing grades adds an uncharacterised junction whose EMF depends on its local temperature. Pick one grade for the whole circuit from sensor to instrument.

What does tolerance Class 1 mean in practice?

It is a limit on how far the cable's EMF may deviate from the Type K reference table over the stated range: ±1.5 °C for Class 1 and ±2.5 °C for Class 2. The figure applies only within that range, which is why the range belongs on the datasheet alongside the class.