Hukseflux HTR02 Series User manual

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USER MANUAL
HTR02 series
Heater for calibration and verification of
performance of FHF-type heat flux sensors
Hukseflux
Thermal Sensors

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Warning 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
Warning statements 2
Contents 3
List of symbols 4
Introduction 5
1Ordering and checking at delivery 7
1.1 Ordering HTR02 7
1.2 Included items 7
1.3 Quick instrument check 8
2Instrument principle and theory 9
2.1 Basic operation 9
2.2 A self-test for heat flux sensors 9
2.3 Using heaters with FHF05 series 10
2.4 Calibrating heat flux sensors 12
2.5 An in-situ test for heat flux sensors 13
3Specifications of HTR02 series 16
3.1 Specifications of HTR02 series 16
3.2 Dimensions of HTR02 series 18
4Installation of HTR02 series 19
4.1 Site selection and installation 19
4.2 Electrical connection 21
5Maintenance and trouble shooting 23
5.1 Recommended maintenance and quality assurance 23
5.2 Trouble shooting 24
5.3 Calibration and checks in the field 24
6Appendices 25
6.1 EU declaration of conformity 25

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List of symbols
Quantities Symbol Unit
Heat flux ΦW/m²
Voltage 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
HTR02 series are heaters that can be used for calibration and functionality checks of FHF-
type heat flux sensors like FHF05 series. The heaters have a 4-wire connection with a
known surface area and electrical resistance. Users can now easily and objectively check
their sensor performance before and after use. HTR02 series is available in two different
models: 50 x 50 and 85 x 85 mm. See also FHF05SC series heat flux sensor with
integrated heater.
Measuring heat flux, users may wish to regularly check their sensor performance. A quick
check or a formal calibration is now possible with HTR02 series plus some accessories
that most laboratories will have in-house. The HTR02 series heaters have a well
characterised traceable surface area and electrical resistance.
In a typical test setup, the heat losses through the insulation are typically smaller than 3
% and may be ignored. Measuring the heater power (voltage Uheater squared divided by
resistance Rheater), and dividing by the surface 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 (Formula 0.1)
The reproducibility of this test is much improved when using contact material between
heater, sensor and heat sink.
HTR02 series has unique features and benefits:
•makes it possible to perform a simple test
•guarantees sensor stability
•matches FHF05 series heat flux sensors
Figure 0.1 On the left model HTR02-85X85 heater for calibration and verification of
performance of the models of FHF05 series heat flux sensors, on the right model FHF05-
85X85 to which HTR02-85X85 may be applied. See also figure 3.2.1 for dimensions.

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HTR02 series is a foil heater and comes in two models. Either it can be used in
combination with foil heat flux sensors such as FHF05 series for test and calibration
purposes, or it can be used as a general-purpose heater.
Options:
•available with standard cable length -02 metre, or change -02 to -05 or -10 metres
for the respective cable length
•cables can also be ordered separately in 2, 5 or 10 metres length
See also:
•FHF05SC heat flux sensor with integrated heater
•FHF05 series general purpose heat flux sensor
•view our complete range of heat flux sensors

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1Ordering and checking at delivery
1.1 Ordering HTR02
The standard configuration of HTR02 series is model 50X50 with 2 metres of cable, order
code: HTR02-50X50-02.
Common options are:
•model HTR02-85X85
•-05 or -10 metres cable length
•with a separate cable in 2, 5 or 10 metres cable length
1.2 Included items
Arriving at the customer, the delivery should include:
•HTR02 heater with cable of the length as ordered
•product certificate matching the instrument serial number
Figure 1.2.1 Model HTR02-50X50 with serial number and resistance 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 heater serial number on the label at the end of HTR02’s cable against the
product certificate provided with the heater.
2. Inspect the instrument for any damage.
3. Check the electrical resistance of the heater between any of the yellow wires and any
of the grey wires. Use a multimeter at the 1 kΩ range. Typical resistance should be
around 120 Ω for 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.
4. Check the electrical resistance between the 2 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 3 grey wires.

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2Instrument principle and theory
HTR02 series is a foil heater. Either it can be used in combination with foil heat flux
sensors such as FHF05 series for test and calibration purposes, or it can be used as a
general-purpose heater.
2.1 Basic operation
If a voltage Uheater is applied to the heater such that an electrical current Iheater runs
through the heater, the heater power Pheater may be calculated as:
Pheater = Uheater∙Iheater = Uheater2/Rheater = Iheater2∙Rheater
where Rheater is the heater electrical resistance. If the heater is placed in a uniform
environment (i.e., same medium on both sides of the heater) the applied heat flux Φ in
either direction may be calculated as:
Φ = Pheater/(2·Aheater) (Formula 2.1.1)
where Aheater is the heater area. If, however, the heater is placed in between a thermal
insulator and a good thermal conductor the heat flux Φ in the direction of the conductor
is:
Φ = Pheater/Aheater (Formula 2.1.2)
Other cases exist as well. Users need to evaluate which case applies to their situation.
2.2 A self-test for heat flux sensors
In combination with a heat flux sensor such as FHF05 series, HTR02 can be used to test
the response of the heat flux sensor. To this end HTR02 should be positioned directly on
top of the heat flux sensor such that HTR02 can be used to apply a heat flux through the
heat flux sensor.
A self-test is started by switching on HTR02, while recording the heat flux sensor output
signal and the HTR02 heater power and finalised by switching HTR02 off. During the
heating interval, Iheater is fed through the foil heater which generates a heat flux
proportional to the heater power. Pheater can be measured in several different ways:
•heater voltage and current, Pheater = Uheater∙Iheater (Formula 2.2.1)
•heater voltage and known heater resistance, Pheater = Uheater2/Rheater (Formula 2.2.2)
•heater current and known heater resistance, Pheater = Iheater2∙Rheater (Formula 2.2.3)
If performed in a four-wire configuration the first method is preferred because it is
generally more accurate than the latter two methods, however it requires both a
voltmeter and an ammeter instead of just one of the two.

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Analysis of the heat flux sensor response to the heating (the self-test) serves several
purposes:
•first, the amplitude and response time under comparable conditions are indicators of
the sensor stability. See 2.5 for application examples.
•second, the functionality of the complete measuring system is verified. For example:
a broken cable is immediately detected.
•third, under the right conditions, after taking the sensor out of its normal
environment, the self-test may be used as calibration. See 2.4 for more details.
Compatible compatible
2.3 Using heaters with FHF05 series
HTR02 series is compatible with the models from the FHF05 series. Model FHF05-50X50
and -85X85 fit directly with HTR02-50X50 and -85X85 respectively.
Models FHF05-10X10 and FHF05-15X30 fit with HTR02-50X50. Model FHF05-15X85 can
be used with HTR02-85X85. Because in these cases the heater is larger than the sensor,
it is recommended to make a guard when using these models with HTR02. See table
2.3.1 for an overview of the models and suggested heaters.
Figure 2.3.1 Using heater model HTR02-50X50 with heat flux sensor FHF05-15X30.
A plastic guard is made with help of a 3D-printer.
To get a representative measurement, the heater should ‘see’ the same environment.
Surrounded by a material like a metal heat sink, the sensor will locally increase the
thermal resistance. The heat from the heater will follow the easiest path; in the case the
heater is larger than the sensor, flow to the metal heat sink. Therefore, the sensor will
measure an underestimation of the actual heat flux.