FHF05 series heat flux sensors

Heat flux sensors that cover most heat flux measurement applications

Sensors of the FHF05 series are suitable for general-purpose heat flux measurement. The range consists of sensor models of five different dimensions. Sensors with larger dimensions have a higher sensitivity and a larger area over which the heat flux is averaged.

Thin, flexible and versatile, FHF05 sensors measure heat flux through the object in which they are incorporated or on which they are mounted, in W/m². The sensor in FHF05 is a thermopile. This thermopile measures the temperature difference across FHF05’s flexible body. A type T thermocouple is integrated as well to provide a measurement of temperature. The thermopile and thermocouple sensors do not require power. 

Multiple small thermal spreaders, which form a conductive layer covering the sensor, help reduce the thermal conductivity dependence of the measurement. With its incorporated spreaders, the sensitivity of the FHF05 sensors is independent of their environment. Many competing sensors do not have thermal spreaders so their sensitivity cannot be relied upon; it depends on the material on which they are mounted. The passive guard area around the FHF05 sensor reduces measurement errors due to edge effects and may also be used for mounting.

Unique features and benefits

• flexible (bending radius ≥ 7.5 x 10⁻³ m)
• low thermal resistance
• wide temperature range 
• fast response time
• large guard area
• integrated type T thermocouple
• robustness, including connection block, for strain relief
• IP protection class: IP67 (essential for outdoor application and in humid environments)
• integrated thermal spreaders for low thermal conductivity dependence
• sensor foil only: may be used in vacuum

Easy to use

Using an FHF05 sensor is easy. It can be connected directly to commonly used data logging systems. The heat flux in W/m² is calculated by dividing the sensor output, a small voltage, by the sensitivity. The sensitivity is provided with the sensor on its certificate.

Heat flux sensors that are robust and stable

Equipped with a potted cable connection block that prevents moisture from penetrating and may also serve as strain relief, FHF05 has proven to be very robust and stable.

FHF05 calibration is traceable to international standards. The factory calibration method follows the recommended practice of ASTM C1130 - 21. 

BLK and GLD sticker series

Would you like to study energy transport / heat flux in detail? Hukseflux helps taking your measurement to the next level: order FHF05 with radiation-absorbing black and radiation-reflecting gold stickers. You can then measure convective + radiative flux with one, and convective flux only with the other. Subtract the 2 measurements and you have radiative flux. There are stickers for every sensor dimension. See the BLK – GLD sticker series user manual and installation video for instructions. Optionally, these stickers can be ordered pre-applied on FHF sensors. 

FluxTeq PHFS-01 and Omega HFS-5 heat flux sensors compared to Hukseflux FHF05 series: test results

For accurate heat flux measurement, sensor buyer may reasonably assume that
• sensitivity does not change over time; stability
• sensitivity as specified on the calibration certificate can be relied upon; that it does not depend on the
environment of the sensor

Testing at Hukseflux reveals that FluxTeq heat flux sensors of model PHFS-01 and Omega heat flux sensors of model HFS-5 are less stable than those manufactured by Hukseflux, and that their sensitivity depends on the environment. In applications that require traceable measurements, users must account for both in their uncertainty evaluation. This leads to a much larger measurement uncertainty than the 5 % stated on the PHFS-01 and HFS-5 calibration certificate.

Read in detail about these test results: FluxTeq heat flux sensor and Omega heat flux sensor.

Image on the right: Close-up of an FluxTeq PHFS-01/Omega HFS-5 heat flux sensor. The thermopile is made using printing technology. Two different metal-filled electrically conducting inks are printed into through-holes.