ISO 9001:2015CE MarkedASTM E1461ISO 22007-2

Thermal Conductivity Tester — High Precision Thermal Conductivity Measurement for Materials Testing

A technical guide to thermal conductivity measurement methods, instrument operating principles, material classification by thermal performance, and test workflows for research, quality control, and materials characterization laboratories.

View Thermal TestersRequest a Quote
0.001 W/mK
Minimum Measurable λ
500 W/mK
Maximum Measurable λ
±2%
Measurement Accuracy
-150 – 700°C
Operating Temp Range

What is a Thermal Conductivity Tester?

A thermal conductivity tester is a precision laboratory instrument used to quantify the rate at which heat flows through a material. Thermal conductivity — expressed as lambda (λ) in units of watts per meter kelvin (W/mK) — is a fundamental material property that governs how materials behave in thermal management applications, insulation systems, building construction, electronics packaging, and aerospace structures.

The instrument applies a controlled heat flux across a specimen of known geometry and measures the resulting temperature gradient. By applying Fourier's Law of Heat Conduction — which states that heat flux is proportional to the negative temperature gradient and the material's thermal conductivity — the instrument calculates the λ value with high accuracy. Modern instruments achieve measurement uncertainty as low as ±1–2% across ranges spanning from aerogels (0.015 W/mK) to metals such as copper (400 W/mK).

Thermal conductivity testers are available in several measurement configurations — guarded hot plate, transient plane source (TPS), laser flash analysis (LFA), and hot wire — each suited to specific material types, temperature ranges, and accuracy requirements. Selection of the appropriate method depends on the specimen form factor, expected conductivity range, and whether steady-state or transient measurements are needed.

Fourier's Law — Core Measurement Principle
q = −λ · (ΔT / Δx)
q = heat flux (W/m²) | λ = thermal conductivity (W/mK)
ΔT = temperature difference | Δx = specimen thickness
1
Apply Known Heat Flux to One Face of Specimen
2
Measure Temperature on Both Surfaces (ΔT)
3
Record Specimen Thickness (Δx) and Cross-Section Area
4
Calculate λ = q · Δx / ΔT — Output Result

Measurement Methods — Flowchart & Comparison

1. Define Material Type
Solid / powder / liquid / film
→
2. Estimate λ Range
Insulator / conductor
→
3. Select Method
GHP / TPS / LFA / Hot Wire
→
4. Prepare Specimen
Size, surface, conditioning
→
5. Set Temperature
Ambient or elevated
→
6. Run Test Cycle
Steady-state or transient
→
7. Read λ Value
W/mK output + report
Guarded Hot Plate (GHP)

Steady-state absolute method. Gold standard for insulation materials. Specimen sandwiched between metered and guard heater plates.

  • Range: 0.01–2 W/mK
  • Best for: foam, fiber, insulation
  • Std: ISO 8302 / ASTM C177
Transient Plane Source (TPS)

Rapid transient method. Flat spiral sensor acts as both heater and thermometer. Suitable for anisotropic and bulk materials.

  • Range: 0.01–500 W/mK
  • Best for: polymers, ceramics, metals
  • Std: ISO 22007-2
Laser Flash Analysis (LFA)

Measures thermal diffusivity. Laser pulse heats one face; IR detector records temperature rise on opposite face. λ = α · ρ · Cp.

  • Range: 0.1–2000 W/mK
  • Best for: metals, composites, ceramics
  • Std: ASTM E1461
Hot Wire / Needle Probe

Transient line-heat-source method. Wire embedded in or inserted into specimen. Fast measurement; suited to loose or granular materials.

  • Range: 0.02–20 W/mK
  • Best for: soils, powders, pastes, liquids
  • Std: ASTM D5334 / ISO 8894

Applications by Industry

Building & Construction Materials

Thermal conductivity measurement of insulation boards, concrete mixes, mortars, aerogels, and glazing systems for energy efficiency rating, U-value calculation, and regulatory compliance under building codes.

Electronics & Thermal Interface Materials

Characterization of thermal interface materials (TIMs), heat sink compounds, gap fillers, PCB laminates, and encapsulants for thermal management in high-power electronics and LED assemblies.

Aerospace & Advanced Composites

Testing of carbon fiber composites, ceramic matrix composites (CMC), thermal protection system tiles, and ablative materials for aircraft, spacecraft, and re-entry vehicle thermal qualification.

Polymers & Plastics

Measurement of bulk thermal conductivity in thermoplastics, thermosets, rubber compounds, and filled polymer systems for product design in automotive, medical device, and consumer goods applications.

Geotechnical & Soil Science

Needle probe measurements of soil, sediment, and rock thermal conductivity for ground-source heat pump design, underground cable routing, and nuclear waste repository site assessment.

Pharmaceutical & Food Science

Thermal property measurement of excipients, active pharmaceutical ingredients, food products, and packaging materials for freeze-drying process design, shelf-life modelling, and cold-chain optimisation.

Material Thermal Conductivity Infographic

λ Values Across Material Classes (W/mK)
Copper / Silver (Metals)385–430 W/mK
Aluminium Alloys150–240 W/mK
Steel / Stainless Steel15–50 W/mK
Dense Ceramics (Al₂O₃)20–30 W/mK
Glass / Concrete0.8–1.8 W/mK
Polymers / Plastics0.1–0.5 W/mK
Foam / Aerogel Insulation0.012–0.04 W/mK
Values are representative ranges at 25°C. Actual λ varies with temperature, density, moisture content, and microstructure.
Method Selection Guide by Material
Metals & alloys (high λ) → Laser Flash Analysis (LFA)
Ceramics & composites → TPS or LFA (depends on form)
Polymers & rubbers → Transient Plane Source (TPS)
Thermal insulation boards → Guarded Hot Plate (GHP)
Soils, powders, pastes → Hot Wire / Needle Probe
Thin films & coatings → 3ω or Modulated DSC method
Liquids & gels → Transient Hot Wire or TPS disk
TPS (ISO 22007-2) covers the widest range of solid material forms and is the most versatile single-instrument method for laboratory QC.

Instrument Architecture Diagram

Specimen
Loading Stage
→
Heating Element
& Heat Flux Sensor
→
Thermocouple
Array (ΔT)
→
Signal Conditioning
& ADC
Temperature
Controller (PID)
→
Data Acquisition
Software
→
λ Result
Report (W/mK)
PID temperature control maintains isothermal boundary conditions; signal conditioning amplifies microvolt thermocouple outputs; software applies Fourier's Law to calculate λ.

Technical Specifications

ISO 9001:2015ISO 22007-2ASTM E1461ASTM C177ISO 8302ASTM D5334EN 12667IEC 61010-1
ParameterSpecificationStandard / Reference
Measurement Range (λ)0.001 – 500 W/mK (method-dependent)ISO 22007-2 / ASTM E1461
Measurement Accuracy±1–2% (traceable calibration)ISO/IEC 17025
Temperature Range-150°C to 700°C (model-dependent)ASTM E1461
Temperature Stability±0.01°C (PID-controlled)ISO 22007-2
Specimen Size (TPS)10 mm – 150 mm diameter discISO 22007-2
Measurement Time40 s – 1800 s (method-dependent)ISO 9001:2015
Heat Flux SensorCalibrated thin-film heat flux transducerASTM C177 / EN 12667
Data OutputUSB / RS-232 / software report (PDF, Excel)ISO/IEC 17025
DisplayTouchscreen LCD + PC software interfaceIEC 61010-1
Power Supply100–240 V, 50/60 HzCE 2014/35/EU

Frequently Asked Questions

Thermal conductivity (λ, W/mK) is an intrinsic material property describing how readily heat flows through a unit volume of material per unit temperature gradient — it is independent of specimen geometry. Thermal diffusivity (α, m²/s) describes how quickly a material responds to temperature changes and equals λ divided by the product of density (ρ) and specific heat capacity (Cp): α = λ / (ρ · Cp). Laser flash analysis directly measures thermal diffusivity, from which λ is calculated when ρ and Cp are known. Thermal resistance (R, m²K/W) is a geometry-dependent property describing the resistance of a specific specimen of given thickness to heat flow; R = thickness / λ. R-value, used in building codes, is thermal resistance expressed in imperial units. All three are related but serve different design and measurement purposes.

For polymer and composite materials in the range 0.1–5 W/mK, the Transient Plane Source (TPS) method per ISO 22007-2 is widely regarded as the most accurate and versatile approach. The TPS sensor — a double spiral of nickel wire sandwiched between two halves of the specimen — acts simultaneously as heater and resistance thermometer. The test takes 40–160 seconds, requires minimal sample preparation, and is suitable for anisotropic materials where in-plane and through-plane conductivities differ. For filled composites with higher conductivity (5–50 W/mK), the laser flash method (ASTM E1461) may provide better accuracy. Guarded hot plate (ISO 8302) offers highest accuracy for low-conductivity polymer foams and films (0.01–0.5 W/mK) but requires longer equilibration times of 30 minutes to several hours.

Thermal conductivity is temperature-dependent for most materials, and the relationship varies by material class. In metals, λ generally decreases with increasing temperature due to increased phonon-electron scattering. In non-metallic crystals and ceramics, λ decreases with temperature as phonon-phonon scattering increases (Umklapp scattering). In amorphous polymers, λ is relatively temperature-insensitive below Tg but may increase slightly above it. In gases and some porous materials, λ increases with temperature. For this reason, measurements must be reported with the specific test temperature, and for materials used across a temperature range, λ(T) curves should be generated by measuring at multiple setpoints. Instruments with variable temperature stages (-150°C to 700°C) enable full characterisation of temperature-dependent thermal conductivity for design database generation.

Specimen preparation requirements depend on the measurement method. For guarded hot plate (GHP) testing, specimens must be flat parallel-faced discs or squares with uniform thickness; surface roughness should be below 10 µm to minimise contact resistance, and multiple specimens may be required (typically two for double-sided configurations). For TPS measurements, two flat-faced specimens are required with contact surfaces ground or polished to achieve intimate contact with the sensor; minimum specimen diameter should exceed the sensor radius by at least 2–3×. For laser flash analysis (LFA), discs of 6–25 mm diameter and 1–6 mm thickness are needed, with both faces coated with thin graphite spray to ensure uniform absorption of the laser pulse and emissivity for the IR detector. For needle probe measurements in soils or pastes, no rigid specimen preparation is required — the probe is simply inserted into the sample container. Moisture content and density must always be recorded as they significantly influence λ.

Thermal conductivity testers are calibrated using Certified Reference Materials (CRMs) with well-characterised, NIST-traceable λ values. Common calibration standards include Pyrex 7740 glass (λ ≈ 1.143 W/mK at 25°C), fused silica (λ ≈ 1.38 W/mK), stainless steel AISI 310 (λ ≈ 14.6 W/mK), and polymethyl methacrylate (PMMA, λ ≈ 0.19 W/mK). For LFA instruments, graphite discs serve as high-temperature reference materials. Calibration should be performed at the beginning of each measurement session and whenever the instrument is relocated or the measurement configuration is changed. Temperature sensor calibration (thermocouples and RTDs) must be verified against NIST-traceable temperature calibrators. Full calibration records, uncertainty budgets, and certificate documentation are required for laboratories operating under ISO/IEC 17025 accreditation or for data submitted to regulatory bodies in building, pharmaceutical, or aerospace applications.

Explore Fison Thermal Conductivity Testers

ISO-certified and CE-marked instruments for materials characterization, quality control, and research applications across insulation, polymers, composites, metals, and geotechnical testing. Contact our team for method guidance, demo requests, and configuration options.

Browse ProductsContact Us