Hukseflux

Thermal Sensors

HFP01

Heat flux plate / heat flux sensor
HFP01 is the world’s most popular sensor for heat flux measurement in the soil as well as through walls
and building envelopes. The total thermal resistance is kept small by using a ceramics-plastic composite
body. The sensor is very robust and stable. It is suitable for long term use on one location as well as
repeated installation when a measuring system is used at multiple locations.

Introduction
HFP01 measures heat flux through the object inwhich it is incorporated or on which it ismounted, in W/m2. The sensor in HFP01 is athermopile. This thermopile measures thetemperature difference across the ceramicsplastic composite body of HFP01. A thermopile isa 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 theHFP01 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 throughwalls and building envelopes.

Unique features and benefits•
Figure 1 HFP01 heat flux plate; the opposite side has a
blue coloured cover

•
••
•
•

low thermal resistance (essential for use on
walls and windows)
large guard area (required by the ISO 9869
standard)
low electrical resistance (low pickup ofelectrical noise)high sensitivity (good signal to noise ratio
in low-flux environments such as buildings)
robustness, including a strong cable
IP protection class: IP67 (essential foroutdoor application)

Calibration
HFP01 calibration is traceable to international
standards. The factory calibration method follows
the recommended practice of ASTM C1130.

Standards

Figure 2 HFP01 heat flux sensor in use

HFP01 can be used for on-site measurement ofbuilding envelope thermal resistance per unit
area (R-value) and thermal transmittance (Uvalue) according to the standardised practices ofISO 9869, ASTM C1046 and ASTM 1155.

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Robust and stable
Equipped with heavy-duty cabling, protective
covers on both sides and potted so that moisturedoes not penetrate the sensor, HFP01 has provento be very robust and stable. It survives longterm installation in soils, as well as repeatedinstallation when a measuring system such as
TRSYS01 is used at multiple locations.

Working with heat flux sensors
A typical measurement location is equipped with
2 heat flux sensors for good spatial averaging. If
the sensitivity of a single sensor is too low, twoor more sensors can electrically be put in series,
creating an amplified single output signal. The
user should analyse his own experiment andmake his own uncertainty evaluation. Moreinformation can be found in the HFP01 manual.
See also our application note how to install aheat flux sensor.

13

HFP01 specifications
Measurand
Sensing area
Guard width to thickness ratio
Sensor thermal resistanceSensor resistance range
Sensor thickness
Uncertainty of calibration
Measurement range
Sensitivity (nominal)
Rated operating temperature
range
Cable diameter
IP protection classStandard cable length
Optionsheat flux
8 x 10-4 m2
5 m/m (as required by
ISO 9869 D.3.1)
71 x 10-4 K/(W/m2)
1 to 4 Ω
5.4 x 10-3 m± 3 % (k = 2)
-2000 to 2000 W/m2
60 x 10-6 V/(W/m2)-30 to +70 oC
4 x 10-3 m
IP675mlonger cable length(10, 15, 20, 30, 40 m)
BLK-80 black sticker
GLD-80 gold sticker

GLD and BLK sticker series
Would you like to to study energy transport / heat
flux in detail? Hukseflux helps taking yourmeasurement to the next level: order HFP01 withradiation-absorbing black and radiation-reflecting
gold stickers. You can then measure convective +radiative flux with one, and convective flux onlywith the other. Subtract the 2 measurements andyou have radiative flux. BLK – GLD stickers can beapplied by the user to the sensor. Optionally, they
can be ordered pre-applied. See the BLK – GLD
sticker series user manual and installation video
for instructions.

2Options
•5m

5.480

Figure 3 HFP01 heat flux plate: (1) sensing area, (2)passive guard of ceramics-plastic composite (3) cable,standard length is 5 m. Total sensor thickness including
covers is 5.4 x 10-3 m. Dimensions in x 10-3 m

Suggested use•••

building heat flux
U-value and R-value measurements
soil heat flux•••

longer cable, in multiples of 5 m, cable
lengths above 20 m in multiples of 10 m
BLK-80 black sticker (to measure radiative
as well as convective heat flux)
GLD-80 gold sticker (to measure convective
heat flux only)
BLK - GLD sticker series can also be ordered
pre-applied at the factory

See also•••

if measuring in soil, in case a high level ofquality assurance and accuracy of themeasurement is needed, consider use ofmodel HFP01SC
model HFP03 for increased sensitivity (alsoconsider putting two or more HFP01’s
electrically in series)
BLK - GLD sticker series to separate radiativeand convective heat fluxes

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Thermal Sensors••

view our complete range of heat flux sensors
view the TRSYS01 building thermal resistancemeasuring system which includes 2 x HFP01
and 4 x matched thermocouple type K•

Figure 4 HFP01 heat flux plate: with BLK-80 and GLD80 stickers to measure radiative and convective heat
fluxes seperately

About Hukseflux
Hukseflux Thermal Sensors offers measurement
solutions for the most challenging applications.
We design and supply sensors as well as test &measuring systems, and offer related services
such as engineering and consultancy. With ourlaboratory facilities, we provide testing services
including material characterisation andcalibration. Our main area of expertise ismeasurement of heat transfer and thermal
quantities such as solar radiation, heat flux andthermal conductivity. Hukseflux is ISO 9001:2008
certified. Hukseflux sensors, systems andservices are offered worldwide via our office in
Delft, the Netherlands and local distributors.

Interested in this product?
E-mail us at: info@hukseflux.com

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MARKET LEADER IN HEAT FLUX MEASUREMENT

HFP01 outperforms competing models: how?
HFP01 is the world’s market leading model for building and soil heat flux measurement. Purchasing a HFP01 is a good investment in accurate and stable measurement.

Durable cable with strain relief
World market leader
HFP01 is on the market for more than 15 years andused by the vast majority of building physics andmeteorological institutes.

60 x 10-6
V/(W/m2)

Low disturbance: small thermal resistance
HFP01 is 5.4 mm thick, but thanks to its ceramicsplastic composite body it is thermally thin. Its thermal
resistance is comparable to 1.4 mm normal plastic,causing little disturbance of the undisturbed heat flux.

Corrosion-proof plastic coverprotecting the complete sensor

Sensitive area with thermal spreader

Continues measuring when others
give up: high sensitivity

High accuracy: passive guard included
A passive guard, i.e. a non-sensitive part aroundthe sensor is essential to avoid errors due toedge effects, HFP01 includes guard according toISO 9869. Competing models often havesensitive parts running to the edge of thesensor, resulting in large potential measurement
errors.

For buildings and soil you need at least
50 x 10-6 V/(W/m2) sensitivity to measuredown to the 0.2 W/m2 level. Competing
sensors are often not sufficiently sensitive,and stop measuring anything significant
while HFP01 can still measure.

Ceramic plastic composite body,equivalent thickness in plastic 1.4 mm
Durable: sturdy “student andinstaller-proof” connection
HFP01’s cable to sensor connection is glued,
and withstands rough handling and repeatedinstallations typical for building applications.
Student and installer-proof! Competing
sensors often have wire connections on
weak solder pads.

Best paperwork

Passive guard area, reducing deflection
errors, also used for mounting

Hukseflux has the paperwork covered;
HFP01 is provided with formally traceablecalibration certificates. We calibrate inaccordance with ASTM C1130.

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