Hukseflux

Thermal Sensors

FHF05SC series

Two self-calibrating foil heat flux sensors with thermal spreaders and heater
Next-level sensors from the world market leader in heat flux measurement, FHF05SC series is a combinationof our standard models FHF05 heat flux sensor and a heater. The heater allows you to perform self-tests,verifying sensor functionality and stability during use, without having to remove the sensor. FHF05SC series
is ideal for high-accuracy and long-term heat flux measurement, construction of calorimeters, (zero heat flux)
core temperature measurement and thermal conductivity test equipment. Available in two models: standard
model size 50X50 mm and a larger size of 85X85 mm.

Introduction
FHF05SC series are sensors for general-purpose
heat flux measurement, combined with a heater. It
is used when the highest level of quality assurance
is required and for long-term heat flux
measurements. It is thin, flexible and versatile.
FHF05SC series measures heat flux through theobject in which it is incorporated or on which it ismounted, in W/m2. The sensor within is athermopile. This thermopile measures thetemperature difference across FHF05SC’s flexible
body. A type T thermocouple is integrated as wellto provide a temperature measurement. Thethermopile and thermocouple are passive sensors;
they do not require power.

Figure 1 Model FHF05SC-50X50 and FHF05SC-85X85
self-calibrating heat flux sensor with heater: thin, flexible
and versatile.

Multiple small thermal spreaders, which form a
conductive layer covering the sensor, help reduce
the thermal conductivity dependence of themeasurement. With its incorporated spreaders, thesensitivity of FHF05SC series is independent of its
environment. Many competing sensors do not havethermal spreaders. The passive guard area aroundthe sensor reduces edge effects and is also used formounting.
Looking only for heat flux and temperature
measurement without the heater: see our FHF05
series heat flux sensors.

Unique features and benefits
•
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•
•
•
•
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Figure 2 FHF05SC-50X50 being installed to measureheat flux on a curved surface.

heater for self-test
flexible (bending radius ≥ 15 x 10-3 m)
low thermal resistancewide temperature range
fast response time
integrated type T thermocouple
robustness, including potted connection
block, may be used as strain relief
IP protection class: IP67 (essential foroutdoor application)

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Thermal Sensors•integrated thermal spreaders for low
thermal conductivity dependence

Using FHF05SC series is easy. For heat flux
measurements, it can be connected directly tocommonly 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 FHF05SC series on
its product certificate. When used under conditions
that differ from the calibration reference conditions,
the FHF05SC series sensitivity to heat flux may bedifferent than stated on its certificate. See the user
manual for suggested solutions.
Make sure your data acquisition accepts type T
thermocouples before doing temperature
measurements.

FHF05SC series specifications
Measurand
Measurand
Temperature sensor
Thermal spreaders
On-line functionality testing
Rated bending radius
Rated load cableOuter dimensions foil with guard
Sensor thermal resistanceSensor thickness
Uncertainty of calibration
Measurement range
Sensitivity (nominal) per model
50X50
85X85
Rated temperature range
continuous use:short intervals:
IP protection classStandard wire length
Heater resistance per model
50X50
85X85
Heater power supply
Optionsheat flux
temperature
type T thermocouple, IEC60584-1:2013 class 2*
included
self-test including selfcalibration≥ 15 x 10-3 m≤ 1.6 kg
(50 x 50) x 10-3 m(85 x 85) x 10-3 m
24 x 10-4 K/(W/m2)
0.7 x 10-3 m± 5 % (k = 2)(-10 to +10) x 103 W/m2
13 x 10-6 V/(W/m2)
50 x 10-6 V/(W/m2)-40 to +120 oC**
-160 to +150 oC*
IP67***
2m
120 Ω (nominal)
40 Ω (nominal)
12 VDC
5 or 10 m cable length
separate cable
BLK black sticker
GLD gold sticker*

temperature measurement uncertainty: 5 % of value in C. For details, refer touser manual.
** rated operating conditions: 120 ˚C continuous use, 150 ˚C short intervals; use
to -80 ˚C is possible.
*** sensor is not suitable for continuous exposure to water.

Suggested use
Figure 3 Working with FHF05SC-85X85 on a metal wall.

•Self-testing
Measuring heat flux, users may wish to regularly
check their sensor performance. During use, thefilm heater is activated to perform a self-test.
The heat flux sensor response to the self-test
results in a verification of sensor performance.
Implicitly also cable connection, data acquisition,
thermal connection of sensor to its environmentand data processing are tested. Heat flux sensors
are often installed for long periods of time. Using
self-testing, the user no longer needs to takesensors to the laboratory to verify their stableperformance. In a laboratory environment, using a
metal heat sink, you may even perform a formal
calibration. The heater has a well characterised andtraceable surface area and electrical resistance.

••••high-accuracy scientific measurement of heat
flux, with a high level of data quality
assurance
study of convective heat transfer mechanisms
calorimeter prototyping(zero heat flux) non-invasive coretemperature measurement
thermal conductivity test equipment

Measurement and control
Requirements for data acquisition and control:•for heat flux: one millivolt measurement•
for heater voltage: one voltage measurement•
optional, for heater current: one current
measurement or voltage measurement over aresistor•
for switching the heater current on and off:
one relay with 12 VDC nominal output

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Thermal Sensors

Calibration
FHF05SC series calibration is traceable tointernational standards. The factory calibration
method follows the recommended practice of
ASTM C1130 - 21.
In a typical calibration setup as shown in figure
3, the FHF05SC series is positioned between an
insulating material and a heatsink with theFHF05SC series heater on the side of theinsulating
material. In such a setup, the heat losses
through the insulation may be ignored.
Measuring the heater power (voltage Uheater square
divided by resistance Rheater), and dividing by thesurface area Aheater, gives the applied heat flux.
The heat flux sensor sensitivity S is the voltage
output Usensor divided by the applied heat flux.
S = (Usensor∙Rheater∙Aheater)/Uheater²
The reproducibility of this test is much improved byusing contact material (such as glycerol or a thermalpaste) between sensor and heat sink.

Figure 5 Calibration of FHF05SC series; a typical stackused for calibration consists of a block of metal (mass > 1kg), for example aluminium (5), the heat flux sensor (3),with heater (2) and an insulation foam (1). Under theseconditions, heat losses through the insulation arenegligible. Heat flux (4) flows from hot to cold.

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, FHF05SC series has proven to be very
robust and stable.

Figure 6 Model FHF05S0C-50X50 and FHF05SC-85X85
heat flux sensors’ front side.

Application exampleFigure 4 FHF05SC series models 50X50 and 85X85
heat flux sensor; Y = 36 or 70, H1 = 47.6 or 82.6 andH2 = 48 or 83.Dimensions in x 10-3 m. (1) sensing
area with thermal spreaders, (2) passive guard, (3)contour of the heater area for self-test, (4) type T
thermocouple, (5) dot indicating front side, (6)connection block for strain relief, (7) cable, standard
length is C = 2 m.

The FHF05SC series heater can be used to checkfor stable performance of the sensor at regularintervals without the need to uninstall the sensor
or to interrupt operation. A typical stability checkis based on the step response of the measured
heat flux and sensor temperature to an appliedheater. Upon installing the sensor, a reference
measurement should be made. A time trace ofthe heater voltage, the measured heat flux andthe measured sensor temperature should bestored as reference measurement.

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Thermal Sensors

Stable operation of the sensor can then beconfirmed at any time by comparing to thereference measurement. The test protocol is asfollows:
1. Make sure that the absolute temperature issimilar to that during the reference measurement
2. Check the heater resistance stability; this canaccurately be done because the connection is 4wire. Subtract wire-to-wire resistance from thewire-sensor-wire resistance.
3. Store the same parameters, normalise withthe heater power. Normally (if the heater isstable) this process scales with V2.
4. Compare patterns of heat flux andtemperature rise and fall during and afterheating. In both cases relative to the values justbefore heating.
• When signal patterns match, but the amplitudediffers (after correction for heater power), thispoints towards sensor instability.
• Non-matching patterns point towards changes
in sensor environment e.g., loss of contact
between sensor and sample.

Figure 7 FHF05SC series heat flux sensor with BLK5050 and GLD-5050 stickers.

See also•••

GLD and BLK sticker series
Would you like to study energy transport / heat
flux in detail? Hukseflux helps taking yourmeasurement to the next level: order FHF05SC
series with radiation-absorbing black andradiation-reflecting gold stickers. You can thenmeasure convective + radiative flux with one, andconvective flux only with the other. Subtract the 2
measurements and you have radiative flux. BLK –GLD stickers can be applied by the user to thesensor. There are stickers for every sensor
dimension. Optionally, they can be ordered preapplied. See the BLK – GLD sticker series user
manual and installation video for instructions.

Options••••••with 5 or 10 metres cable length
separate cable in 2, 5 or 10 metres length
LI19 hand-held read-out unit / datalogger
NOTE: LI19 measures heat flux only, nottemperature, does not support the self-test
functionality
BLK black sticker (to measure radiative
as well as convective heat flux)
GLD gold sticker (to measure convective heatflux only)
BLK - GLD sticker series can also be ordered
pre-applied at the factory••

FHF05 series, our standard model for
general-purpose heat flux measurement
model HFP01 for increased sensitivity (alsoconsider putting two or more FHF05s in series)
model HTR02, a loose heater for calibrationand verification of performance of FHF typesensors
BLK - GLD sticker series to separate radiativeand convective heat fluxes
Hukseflux offers a complete range of heat flux
sensors with the highest quality for any budget

About Hukseflux
Hukseflux is the leading expert in measurementof energy transfer. We design and manufacture
sensors and measuring systems that support theenergy transition. We are market leaders in solar
radiation- and heat flux measurement.
Hukseflux products and services are offeredworldwide 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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