RTD-PT100-3/4W

Pt100 RTD Signal Cable — 3-Wire and 4-Wire Screened Construction

Screened triples and quads that keep lead resistance out of the temperature reading.

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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.

A Pt100 is a resistor, nominally 100 Ω at 0 °C and changing by 0.385 Ω per kelvin to IEC 60751. That sensitivity is what makes it accurate and what makes it vulnerable: the instrument cannot distinguish resistance in the sensor from resistance in the copper that reaches it, so 1 Ω of lead resistance reads as 2.6 °C. The third and fourth wires are the industry's answer.

Voltcore builds this cable as a screened twisted triple or quad rather than as a multi-core, because the cancellation a three-wire circuit depends on requires all three conductors to be identical in length, cross-section and termination. Cores are twisted together with a short lay length so they share the same route and the same temperature, then screened with foil and braid — the signal is only 100 mV or so across the sensor at typical excitation currents.

Specification

Pt100 RTD signal cable — Technical Specification
Item	Value
Sensor type	Pt100 to IEC 60751, α = 0.00385 Ω/Ω/°C
Connection	3-wire (compensated) or 4-wire (Kelvin)
Conductor	Class 5 flexible plain annealed copper, IEC 60228
Cross-section range	0.5 – 2.5 mm²
Construction	3-core or 4-core twisted, laid up as one triple or quad
Insulation	PVC or polyethylene
Screen	Aluminium foil plus tinned copper braid ≥ 85 % coverage, with tinned drain wire
Sheath	PVC grey or black; LSZH and blue Ex i variants available
Max. continuous conductor temperature	70 °C
Test voltage	2 kV rms core to core, 1 kV rms core to screen, 5 min
Minimum bending radius	10 × cable overall diameter
Core identification	Three red cores for 3-wire; colour-coded pairs for 4-wire

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, identical construction in every core
2. InsulationPVC or polyethylene extruded at 0.5–0.7 mm wall, colour coded for polarity identification
3. TwistingThree or four cores twisted together at a short lay length so all leads follow the same route and temperature
4. Foil screenAluminium-laminated polyester foil applied with overlap, 100 % coverage, with a tinned drain wire
5. Braid screenTinned copper wire braid at ≥ 85 % coverage over the foil
6. SheathPVC grey or black, 1.0–1.5 mm nominal; LSZH and light blue Ex i variants available

Reference dimensions and weights

Pt100 RTD cable — 4-core dimensions, lead resistance and error (reference figures)
Cores × cross-section (mm²)	Conductor structure (No./mm)	Insulation thickness (mm)	Approx. overall diameter (mm)	Approx. weight (kg/km)	Lead resistance per conductor at 100 m (Ω)	Approximate 2-wire measurement error at 100 m (°C)
4×0.5	16/0.20	0.5	7.2	95	3.90	20.3
4×0.75	24/0.20	0.5	7.8	120	2.60	13.5
4×1.0	32/0.20	0.6	8.6	150	1.95	10.1
4×1.5	30/0.25	0.6	9.4	195	1.33	6.9
4×2.5	50/0.25	0.7	11.0	280	0.80	4.2

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

Cores built to identical construction, which is what the three-wire cancellation assumes
0.385 Ω/K sensitivity means 1 Ω of lead resistance is about 2.6 °C, so conductor size is a measurement decision
Foil plus braid screen, because the sensor voltage is only tens of millivolts at typical excitation
Short twist lay length keeps all leads at the same temperature, so their resistances track together
0.5–2.5 mm² range: 1.5 mm² gives 1.33 Ω per 100 m lead and about 6.9 °C of two-wire error at that distance
Class 5 conductors for termination in a transmitter head or a panel terminal
3-core and 4-core constructions, plus multi-triple versions for multi-point monitoring

Typical applications

Pt100 sensors on process plant connected to a temperature transmitter or PLC input card
Bearing and winding temperature monitoring on motors, pumps and generators
HVAC, chilled water and building management temperature loops
Food, pharmaceutical and clean steam applications with hygienic RTD probes
Calibration laboratory and test bench wiring using four-wire measurement

Ordering options

3-core or 4-core construction, or multiple triples in one sheath
Foil screen with drain wire, or foil plus braid composite
LSZH sheath to IEC 60754-1 and IEC 61034-2
Light blue sheath with documented capacitance and inductance for Ex i circuits
Polyethylene insulation where lower capacitance is required on long runs

Standards manufactured to

IEC 60751 (industrial platinum resistance thermometers)
IEC 60228 Class 5 (conductor)
IEC 60332-1-2 (flame propagation)
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 Pt100 RTD 3-Wire & 4-Wire Signal 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

or sales@cable-export-manufacture.com · WhatsApp

Pt100 RTD 3-Wire & 4-Wire Signal Cable — frequently asked questions

Why does a three-wire connection cancel lead resistance?

The instrument measures the sensor through one lead and senses the voltage through two others, then subtracts the drop in a shared lead. The cancellation only holds if all three leads have equal resistance, which is why the cores in this cable are built identically and twisted together.

When is a four-wire connection worth the extra core?

When you are calibrating or measuring to better than a few tenths of a degree. A four-wire circuit drives a constant current through one pair and senses voltage through the other, so no current flows in the sense leads and their resistance is irrelevant regardless of length or balance.

What cross-section should I use for a 100 m Pt100 run?

1.5 mm² gives 1.33 Ω per lead at 100 m, which a three-wire input cancels almost entirely. If you must use a two-wire connection, the same run leaves about 6.9 °C of error, so either move to three-wire or increase the section and calibrate the offset out.

Can thermocouple cable be used for a Pt100?

No. Thermocouple extension conductors are nickel alloys with a resistivity roughly forty times that of copper, so they would add tens of ohms of lead resistance and a large error. RTD circuits need copper conductors throughout.