Hukseflux FHF05SC Series User manual

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USER MANUAL
FHF05SC series
Self-calibrating foil heat flux sensor with thermal
spreaders and heater
Hukseflux
Thermal Sensors

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Cautionary statements
Cautionary statements are subdivided into four categories: danger, warning, caution and
notice according to the severity of the risk.
DANGER
Failure to comply with a danger statement will lead to death or serious
physical injuries.
WARNING
Failure to comply with a warning statement may lead to risk of death or
serious physical injuries.
CAUTION
Failure to comply with a caution statement may lead to risk of minor or
moderate physical injuries.
NOTICE
Failure to comply with a notice may lead to damage to equipment or may
compromise reliable operation of the instrument.

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Contents
Cautionary statements 2
Contents 3
List of symbols 4
Introduction 5
1Ordering and checking at delivery 9
1.1 Ordering FHF05SC series 9
1.2 Included items 9
1.3 Quick instrument check 10
2Instrument principle and theory 11
2.1 Theory of operation 11
2.2 The self-test 14
2.3 Calibration 14
2.4 Application example: stable performance check 15
2.5 Application example: non-invasive core temperature measurement 18
3Specifications of FHF05SC series 19
3.1 Specifications of FHF05SC series 19
3.2 Dimensions of FHF05SC series 22
4Standards and recommended practices for use 23
4.1 Heat flux measurement in industry 23
5Installation of FHF05SC series 24
5.1 Site selection and installation 24
5.2 Installation on curved surfaces 26
5.3 Electrical connection 27
5.4 Requirements for data acquisition / amplification 30
6Maintenance and trouble shooting 31
6.1 Recommended maintenance and quality assurance 31
6.2 Trouble shooting 32
6.3 Calibration and checks in the field 34
7Appendices 35
7.1 Appendix on cable extension 35
7.2 Appendix on using FHF05SC series with BLK – GLD sticker series 36
7.3 Appendix on standards for calibration 37
7.4 Appendix on calibration hierarchy 37
7.5 Appendix on correction for temperature dependence 38
7.6 Appendix on measurement range for different temperatures 39
7.7 Appendix on temperature measurement accuracy 40
7.8 EU declaration of conformity 42

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List of symbols
Quantities Symbol Unit
Heat flux ΦW/m²
Voltage output U V
Sensitivity S V/(W/m2)
Temperature T °C
Thermal resistance per unit area Rthermal,A K/(W/m²)
Area A m²
Electrical resistance R Ω
Electrical power P W
subscripts
property of heatsink heatsink
property of heater heater
property of sensor sensor
maximum value, specification limit maximum

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Introduction
FHF05SC series is a combination of the standard model FHF05 heat flux sensor and a
heater. The heater allows the user to perform self-tests, verifying sensor functionality
and stability during use, without having to remove the sensor. FHF05SC series are 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: size 50X50 mm and a larger size of 85X85 mm.
FHF05SC series measures heat flux through the object in which it is incorporated or on
which it is mounted, in W/m2. The sensor within is a thermopile. This thermopile
measures the temperature difference across FHF05SC’s flexible body. A type T
thermocouple is integrated as well to provide a temperature measurement. 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 FHF05SC series is independent of its
environment. Many competing sensors do not have thermal spreaders. The passive guard
area around the sensor reduces edge effects and is also used for mounting. Looking for
only heat flux and temperature measurement without a heater? See our FHF05 series heat
flux sensors.
Figure 0.1 Model FHF05SC-50X50 self-calibrating foil heat flux sensor with thermal
spreaders and heater, showing its back and front side.

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Measuring heat flux, users may wish to regularly check their sensor performance. During
use, the film 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 wire
connection, data acquisition, thermal connection of the sensor to its environment and
data processing are tested. Heat flux sensors are often kept installed for as long as
possible. Using self-testing, the user no longer needs to take sensors to the laboratory to
verify their stable performance. In a laboratory environment, using a metal heat sink,
you may even perform a formal calibration. The heater has a well characterised and
traceable surface area and electrical resistance.
The FHF05SC series self-calibrating foil heat flux sensor has unique features and
benefits:
•heater for self-test
•flexible (bending radius ≥ 15 x 10-3 m)
•low thermal resistance
•wide temperature range
•fast response time
•integrated type T thermocouple
•robustness, including cable and connection block which may be used as strain relief
•IP protection class: IP67 (essential for outdoor application)
•integrated thermal spreaders for low thermal conductivity dependence
FHF05SC series suggested use:
•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 core temperature measurement
•thermal conductivity test equipment
\
Figure 0.2 Application example: FHF05SC-50X50 being installed to measure heat flux on
a pipe. The sensor is mounted on a well-prepared curved surface.

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Using FHF05SC series is easy. It can be connected directly to commonly used data logging
systems. The heat flux in W/m2is calculated by dividing the sensor output, a small voltage,
by the sensitivity. The sensitivity is provided with FHF05SC series on its product certificate.
Equipped with a protective potted connection block, which may serve as strain relief so
that moisture does not penetrate, FHF05SC series has proven to be very robust and
stable.
FHF05SC series calibration is traceable to international standards. The factory calibration
method follows the recommended practice of ASTM C1130 - 21. When used under
conditions that differ from the calibration reference conditions, the FHF05SC series
sensitivity to heat flux may be different than stated on its certificate. See Chapter 2 in
this manual for suggested solutions.
Would you like to study energy transport / heat flux in detail? Hukseflux helps taking this
measurement to the next level: order FHF05SC series 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. They can be applied to the sensor by the user or at the factory; see the BLK
– GLD sticker series user manual and installation video for instructions.
Figure 0.3 FHF05SC-50X50 heat flux sensor: with BLK-5050 and GLD-5050 stickers.

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See also:
•FHF05 series, our standard model for general-purpose heat flux measurement
•model HFP01 for increased sensitivity (also consider putting two or more FHF05s in
series)
•HTR02 series heater, for calibration and verification of performance of FHF-type sensors.
•BLK - GLD sticker series to separate radiative and convective heat fluxes
•Hukseflux offers a complete range of heat flux sensors with the highest quality for any
budget

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1Ordering and checking at delivery
1.1 Ordering FHF05SC series
The standard configuration of FHF05SC series is FHF05SC-50X50-02, model 50X50 with
2 metres of cable. Common options are:
•model FHF05SC-85X85
•change -02 to -05 or -10 metres cable length
•with a separate cable in 2, 5 or 10 metres cable length
•with LI19 hand-held read-out unit / datalogger; NOTE: LI19 does not measure
temperature, only heat flux and does not support self-test functionality
•BLK black sticker (to measure radiative as well as convective heat flux)
•GLD gold sticker (to measure convective heat flux only)
•BLK - GLD sticker series can also be ordered pre-applied at the factory for every
sensor dimension
1.2 Included items
Arriving at the customer, the delivery should include:
•heat flux sensor FHF05SC with cable of the length as ordered
•product certificate matching the instrument serial number
Figure 1.2.1 Model FHF05SC-50X50 with serial number and sensitivity shown at the end
of the cable.

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1.3 Quick instrument check
A quick test of the instrument can be done by connecting it to a multimeter.
1. Check the sensor serial number and sensitivity on the sticker on the potted connection
block against the product certificate provided with the sensor.
2. Inspect the instrument for any damage.
3. Check the electrical resistance of the sensor between the red [+] and black [-] wires.
Use a multimeter at the 1k Ω range. Measure the sensor resistance first with one
polarity, then reverse the polarity. Take the average value. The typical resistance of the
wiring is 0.3 Ω/m. Typical resistance should be the nominal sensor resistance mentioned
in table 3.1.1 plus 0.6 Ω for the total resistance of two wires for each metre (back and
forth). Infinite resistance indicates a broken circuit; zero or a lower than 1 Ω resistance
indicates a short circuit.
4. Check the electrical resistance of the thermocouple between the brown [+] and white
[-] wires. Use a multimeter at the 100 Ω range. Measure the thermocouple resistance
first with one polarity, then reverse the polarity. Take the average value. The typical
resistance of the copper wiring is 0.3 Ω/m, for the constantan wiring this is 6.5 Ω/m.
Typical resistance should be the nominal thermocouple resistance of 2.5 Ω plus 6.8 Ω for
the total resistance of the two wires of each metre (back and forth). Infinite resistance
indicates a broken circuit; zero or a lower than 1 Ω resistance indicates a short circuit.
5. Check if the sensor reacts to heat: put the multimeter at its most sensitive range of
DC voltage measurement, typically the 100 x 10-3 VDC range or lower. Expose the sensor
to heat. Exposing the back side (the side with the heater) to heat should generate a
positive signal between the red [+] and black [-] wires. Doing the same at the front side
(the side with the dot), reverses the sign of the output.
6. Check the electrical resistance of the heater between purple or yellow wire and pink or
green wire. Use a multimeter at the 1 kΩ range. Typical resistance should be around 120
Ωfor model -50X50 and around 40 Ω for model -85X85 . Infinite resistance indicates a
broken circuit; zero or a lower than 1 Ω resistance indicates a short circuit. 7. Check the
electrical resistance between the purple and yellow wires. . These resistances should be
in the 0.1 Ω/m range, so 0.2 Ω in case of the standard 2 m wire length. Higher
resistances indicate a broken circuit. Repeat this measurement for the pink and green
wire.