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 five different dimensions. Larger dimensions mean a higher sensitivity and a larger area over which the heat flux is averaged. They are thin, flexible and versatile. FHF05 measures heat flux through the object in which it is incorporated or on which it is 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. The thermopile and thermocouple are passive sensors; they 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 FHF05 is independent of its environment. Many competing sensors do not have thermal spreaders. The passive guard area around the sensor reduces measurement errors due to edge effects and is also 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)
• integrated thermal spreaders for low thermal conductivity dependence

Easy to use

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

Heat flux sensors that are robust and stable

Equipped with a connection block, which may serve as strain relief, and with potted protective covers on both sides so that moisture does not penetrate, 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 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. BLK – GLD stickers can be applied by the user to the sensor. There are stickers for every sensor dimension. Optionally,  they can be ordered pre-applied. See the BLK – GLD sticker series user manual and installation video for instructions.

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.