The World’s Most Popular Sensor for Heat Flux Measurement
HFP01 measures heat flux through the object in which it is incorporated or on which it is mounted, in W/m². The sensor in HFP01 is a thermopile. This thermopile measures the temperature difference across the ceramics-plastic composite body of HFP01. A thermopile is a passive sensor; it does not require power. Using HFP01 is easy. It can be connected directly to commonly used data logging systems. The heat flux in W/m² is calculated by dividing the HFP01 output, a small voltage, by the sensitivity. The sensitivity is provided with HFP01 on its calibration certificate. A typical measurement location is equipped with 2 or more sensors. HFP01 is the world’s most popular sensor for heat flux measurement in the soil as well as through walls and building envelopes.
Robust and Stable
Equipped with heavy-duty cabling, protective covers on both sides and potted so that moisture does not penetrate the sensor, HFP01 has proven to be very robust and stable. It survives longterm installation in soils, as well as repeated installation when a measuring system such as TRSYS01 is used at multiple locations.
- Building heat flux
- U-value and R-value measurements
- Soil heat flux
Application of this instrument
Areas of Application
Building physics / insulation, thermal comfort and energy budget measurement
Geotechnics / soil thermal route analysis
Material characterization / thermal conductivity measurement
Meteorology / surface energy flux measurement
Scientific research / heat and heat transfer measurement
|Measurement range||-2000 to +2000 W/m²|
|Sensitivity (nominal)||60 x 10⁻⁶ V/(W/m²)|
|Sensing area||8 x 10⁻⁴ m²|
|Guard width to thickness ratio||5 m/m (as required by ISO 9869 D.3.1)|
|Sensor thermal resistance||71 x 10⁻⁴ K/(W/m²)|
|Sensor thickness||5.4 x 10⁻³ m|
|Uncertainty of calibration||± 3 % (k = 2)|
|Rated operating temperature range||-30 to +70 °C|
|Cable diameter||4 x 10⁻³ m|
|IP protection class||IP67|
|Standard cable length||5 m|
|Options||longer cable length (10, 15, 20, 30, 40 m)
• LI19 hand held readout unit
Frequently asked questions
Heat flux sensors measure energy flux onto or through a surface in [W/m²].
The source of the heat flux may be:
Convective and conductive heat transfer are associated with a temperature difference. Heat always flows from a source to a sink, from a hot to a cold environment. Convective and conductive heat flux is measured by letting this heat flow through the sensor. Radiative flux is measured using heat flux sensors with black absorbers. The absorbers converts radiative to conductive energy. Hukseflux started in 1993 with sensors for measurement of heat flux in soils and on walls. In the course of the years, we have added specialised sensors and systems for many other applications.
Heat flux sensors manufactured by Hukseflux are optimised for the demands of different applications:
- rated temperature range
- rated heat flux range
- response time
- chemical resistance, safety requirements
- size, shape and spectral properties
Hukseflux is the world market leader in heat flux measurement. We have prepared a white paper briefly explaining the fundamentals of measuring with heat flux sensors. It also offers general directions what to watch out for and some, perhaps surprising, applications of heat flux sensors. Take a look at our white papers.
There are quite a few general considerations when starting a heat flux measurement.
- Representativeness in time and space; average!
A heat flux sensor measures at a certain location. Is this location representative of what you need to measure? If possible, use a relatively large sensor, rather than a small one, and consider use of multiple sensors. Thermal processes often have large time constants; instantaneous measurements may be misleading. Average to get the full picture.
- Optical properties
When heat flux sensors also measure radiation, pay attention to the surface color. If needed paint the sensor surface. Please mind that shiny metallic surfaces reflect both infra-red and visible radiation. Paints may have different colors in the visible range, but are usually “black” absorbers in the far-infra-red.
- Sensor thermal resistance
A heat flux sensor distorts the local heat flux. In order to minimize this effect, use the sensor with the lowest possible thermal resistance.
- Edge effects
A heat flux sensor locally distorts the heat flow pattern, in particular around the edges of the sensor. A passive guard, i.e. a non-sensitive part around the sensor is essential to avoid errors due to edge effects.
There are more characteristics that matter. Please find them in our white paper on heat flux fundamentals and applications.
Hukseflux manufactures a range of sensors for surface energy flux measurements. All have proven reliability.
These state-of-the-art sensors are made for the global fluxnet community:
- NR01 is a market leading 4-component net radiometer.
- HFP01 and HFP01SC measure soil heat flux.
- STP01 offers an accurate temperature profile measurement.
- TP01 is the leading sensor for soil thermal conductivity.
Sensors made by Hukseflux are designed for compatibility with most common datalogger models. For many models we have example programs and wiring diagrams available.
On-site measurements of thermal resistance, R, are often applied in studies of buildings. Alternatives are to measure its inverse value, the thermal conductance which is called the Λ-value, or the thermal transmittance which includes ambient air boundary layer thermal resistance, the U-value. The measurements of R are based on simultaneous time averaged measurement of heat flux Φ and differential temperature, ΔT, (using two temperature sensors on each on a different side of the wall).
R = ΔT / Φ
Hukseflux provides a range of sensors and measuring systems for use in measurement of the energy budget of buildings and characterization of construction materials.
HFP01 heat flux sensor and TRSYS01 measuring system are widely used for on-site measurements on walls, windows and other construction elements in building physics.
- HFP01 can be used for in-situ measurement of building envelope thermal resistance (R-value) and thermal transmittance (H-value) according to ISO 9869, ASTM C1046 and ASTM 1155 standards. HFP01 is the world’s most popular sensor for heat flux measurement in the soil as well as through walls and building envelopes. HFP01 measures heat flux through the object in which it is incorporated or on which it is mounted, in W/m². More information? Visit the HFP01 product page.
- TRSYS01 is a high-accuracy system for on-site measurement of thermal resistance, R, thermal conductance, the Λ-value, and thermal transmittance, the U-value, of building envelopes. TRSYS01 is mostly used for measurements according to standard practices of ISO 9869 and ASTM C1155 / C1046. The system is equipped with high-accuracy electronics, two heat flux sensors of model HFP01 as well as two pairs of matched thermocouples. The two measurement locations provide redundancy, leading to a high level of confidence in the measurement result. The high accuracy of the heat flux sensors and temperature difference measurements ensures that TRSYS01 continues measuring when other systems no longer perform; in particular at very low temperature differences across the wall.
Hukseflux, market leader in heat flux measurement, offers both sensors and systems.
These measuring systems typically include a Measurement and Control Unit and one or more sensors for measuring heat flux as well as other measurands, such as temperature and humidity. Examples are the TCOMSYS01 Hot Cube thermal comfort measuring system, including a TCOM01 sensor, and the TRSYS01 measuring system, incorporating two HFP01 heat flux sensors and two pairs of matched thermocouples.
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