Fox 801

Measurement Technique

Samples are placed between two plates in the test stack and a temperature gradient is established over the thickness of the material. The plates may be positioned either to a user-defined thickness, or using AutoThickness, in which the instrument automatically moves to establish contact with the sample. In-situ sample thickness is measured with four optical encoders, one at each corner of the plate, providing stable measurements to within 0.025 mm.

Advanced Heat Flux Measurement

At the heart of the measurement is the LaserComp Heat Flux Transducer, designed and manufactured specifically and exclusively for thermal conductivity measurements. The Heat Flux Transducer integrates over the entire active area (254x254mm / 10 sq. in.) to provide a truly representative measurement of the total heat flow. Overall transducer thickness is less than 1 mm, precluding heat flow distortion. A type E thermocouple is bonded in the center of each transducer and both are sealed to ensure consistent precision over the life of the instrument. Because each thermocouple is positioned within 0.1 mm of the sample surface, they provide truly representative readings of the sample’s surface temperature (± 0.01 °C resolution) and heat flux. The same thermocouples are also used for plate temperature control.

Precision Temperature Control

The FOX series Heat Flow Meters achieve accurate, stable thermal equilibrium quickly through a combination of intimate sample temperature measurement, low mass solid state elements and advanced temperature control electronics.

Plate temperature control is based on the same responsive thermocouples in close sample contact as are used for the sample heat flux measurement. An advanced temperature control algorithm monitors the plate temperatures 20 times per second and rapidly brings the system to the selected equilibrium test condition. Plate temperature is controlled to within 0.01 °C by a digital signal processor. A multistage PID algorithm ensures temperature control which is responsive, stable, and prevents set-point overshoot. To achieve this, heater power output from the solid state elements is adjusted every 0.5 s.

Both the top and bottom plates can be heated or cooled, allowing for testing with heat flow up or down. The low thermal mass design of the plates combined with the power of the DSP and power output board enable extremely fast attainment of set-points.

Complete Thermal Conductivity Solution

The FOX series Heat Flow Meters can be operated as either stand-alone instruments, or coupled to a PC for test set-up and data storage. The WinTherm software package is a user-friendly tool for setting experimental parameters, viewing real-time test results, storing, and analyzing data. In either operational mode, the instrument electronics detect equilibrium according to defined conditions, automatically proceeding to the next programmed measurement temperature after a final value is collected. Specific heat measurements are also available, with data collection and calculation guided by the WinTherm software.

External Thermocouple Kit

Thermocouples are attached directly to the sample surfaces, eliminating the impact of interface resistance, and improving the measurement accuracy for higher thermal conductivity samples (up to 2.5 W/m K). In case of rigid specimens the external thermocouples can be also placed in grooves machined in the sample. Instruments configured for this option feature auxiliary outlets for the external thermocouples.

Rotational System

The FOX 801 Heat Flow Meter can be configured with the innovative Rotational System from LaserComp. Understanding the complex combination of heat transfer mechanism present in field installations, the Rotational System allows to measure thermal conductivity under conditions matching real-life material’s orientation. The rugged system allows the motorized rotation of the test system to a user-defined angle between 0° and 90°. This allows for the exact, representative, simulation of conditions present in roofs, walls, skylights, and more.