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Release 1.0 Operating Manual Thermoelectric Heat Flux Sensors HRX SERIES
THERMOELECTRIC HEAT FLUX SENSORS Page 2 of 32 CONTENT 1. INTRODUCTION 5 Features 5 2. SPECIFICATIONS 6 Numbering system 7 3. QUICK START 8
3.1 About Heat Sensor HRX series 8
3.2 Preparations for working 8
3.3 Sensor testing 9
3.4 Sensor calibration 9
3.5 Mounting of the Sensor 9
3.6 Data acquisition 10
3.7 How to calculate heat flux 10
3.8 Sensors service 10
- HEAT FLUX SENSORS INTRODUCTION 11
4.1 Description of installation 11
- FUNCTIONALITY TEST 12
5.1 Checking of AC Resistance 12
5.2 Checking of Figure-of-Merit. 12
5.3 Checking of Sensor behavior 13
- INSTALLATION OF SENSORS 14
6.1 Mounting circuit board 14
6.2 Soldering profile 14
- DATA ACQUISITION 16
7.1 Datalogger DX8140 16
7.2 Voltmeter as a read-out device 16
7.3 Third party read-out device 17
OPERATING MANUAL. HRX SERIES Page 3 of 32 8. DATA ANALYSIS 18
8.1 Temperature corrections 18
Example for calculating 20
8.2 Heat flux measurements 21
Example for heat flux measurement 22 9. SELF-CALIBRATION PROCEDURE 23
9.1 Method 23
9.2 Measurement Scheme 24
9.3 Equipment 25
9.4 Example 25
- MAINTENANCE OF THE SENSOR 26
10.1 Removing Sensor from measurement setup 26
10.2 Cleaning of Sensor 26
10.3 Storage 26
- ADDITIONAL INFORMATION 27
11.1 Electromagnetic field 27
11.2 Application in temperatures outside of calibration range 27
11.3 Use in fluids 27
- DEFINITIONS 28
THERMOELECTRIC HEAT FLUX SENSORS Page 4 of 32 Edition April 2015 Copyright All rights reserved. Reproduction in any manner, in whole or in part is straightly prohibited without written permission of RMT Ltd. The information contained in this document is the subject to change without notice. Limited Warranty RMT Ltd. warrants that the Thermoelectric Heat Flux Sensor of HRX Series, if properly installed and used, will be free of defects in material and workmanship and will subs tantially conform to RMT’s publicly available specification for a period of one (1) year after the date that the Thermoelectric heat Flux Sensor of HRX Series was purchased. If the Thermoelectric heat Flux Sensor of HRX Series, which is the subject of this Limited Warranty, fails during the warranty period for the reasons covered by this Limited Warranty, RMT, at this option, will: REPAIR the Thermoelectric heat Flux Sensor of HRX Series; OR REPLACE the Thermoelectric heat Flux Sensor of HRX Series with another unit of the same model. Trademark Acknowledgments All trademarks are the property of their respective owners. RMT Ltd.
46 Warshavskoe shosse, Moscow 115230 Russia
phones: +7-499-678-20-82 e-mail: info@rmtltd.ru www.rmtltd.ru
OPERATING MANUAL. HRX SERIES Page 5 of 32 1. INTRODUCTION Heat Flux Sensors of HRX series – the series of high sensitive and self - calibrating miniature sensors for radiation heat fluxes.
Features
- High sensitivity - Miniature design - Self-calibrating - SMD style - A range of customized dimensions The Sensors are developed as a series of sizes: 4x4 and 6x6 mm2. Optional dimensions (size and thickness) as well as customized performance parameters are available on request. The Sensors have wireless package of SMD style, suitable for SMD mounting by flip-chip method. Connectors of the sensors come out to back side of the package. The Sensors were developed for measurement of radiation heat fluxes in a wide range of heat flux intensities. The high sensitivity of the Sensors of the series p rovides accurate experiments and data on objects of investigations. One of the feature of the Sensors is the self -calibration method (patent pending RU2014145948 dated 17.11.2014). It means possibility to calibrate precisely the Sensor by measurement of it s thermoelectric performance parameters. It is not necessary to remove it and send to labs. The calibration procedure is possible with use of RMT Datalogger of the DX8140 series, specially developed for thermoelectric heat flux Sensors, or by use of RMT Z -meters. The calibration procedure is described in Chapter 10.
THERMOELECTRIC HEAT FLUX SENSORS Page 6 of 32 2. SPECIFICATIONS Product name HRD HRD HRD 02-040-03L04 02-040-05L04 03-040-05L06 Detector1) Type Thermal - thermoelectric Surface material Ceramics, painted black Protection2) IP67 Surface dimensions AxB, mm2 4x4 4x4 6x6 Thickness H, mm 0,8 1 1 Surface blackness 0,95 0,95 0,95 Sensitivity Se, mV/(W/m2) 11 18 18 Integral Sensitivity Sa, V/W 0,68 1,14 0,51 Detectivity, cmHz1/2/W 1,30E+09 1,70E+09 1,70E+09 Time Constant , s 0,4 0,7 0,7 Electrical Resistance ACR, Ohm 6,0 10,0 4,4 Power Density max Pe, ±W/m2 14 500 9 000 9 000 Maximal Power Pa, ±W 0,24 0,14 0,32 Thermal Resistance RT, K/(W/m2) 6,80E-04 1,30E-03 1,30E-03 Integral Thermal Resistance RT, K/W 42,4 70,5 31,3 Temperature Dependence3) dS/dT, %/°C 0,25 0,25 0,25 Linearity with Power dS/dP, ±%/(W/m2) 0,01% 0,02% 0,02% Homogeneity dS/dA, ±% 1 1 1 Calibration Accuracy, ±% 3 3 3 Calibration Temperature Range Min/Max, °C] Operating Temperature Range Min/Max, °C Soldering Temperature4) Max, °C +260 +260 +260 Cooling Method Convection Electric Connection Bottom side Notes: 1) Performance data shown in the S pecifications are given for ambient temperature Ta=300 K (27 °C) 2) Application in water - not more than 1 hour. Maximal temperature 100°C. 3) Average value. Detailed temperature dependence is given in table 4) Maximal duration 5 minutes.
OPERATING MANUAL. HRX SERIES Page 7 of 32 Numbering system The following numbering system was developed to order thermoelectric heat flux sensors of RMT. The sensor serial number gives some useful information about design of the sensors. H R X - 0 4 0 - 0 4 Х 0 4 Description Dimensions in mm Shape: D - dia. (round sensor) L - square sensor Pellet height, mmх10 Number of pellet pairs Type of thermoelectric module used: MC «C» MD «D» Sensor type: HT heat flux and temperature HF heat flux (without temperature) HR radiation heat flux
THERMOELECTRIC HEAT FLUX SENSORS Page 8 of 32 3. QUICK START
3.1 About Heat Sensor HRX series
The Heat Flux Sensors of the HRX series – the series of high sensitive and self-calibrating miniature Sensors. The Sensors were developed for measurement of radiation heat fluxes in a wide range of intensities. The Sensors are developed as a series of sizes: 4x4 and 6x6 mm 2. Optional dimensions (size and thickness) as well as customized performance parameters are available on request. The Sensors have wireless package of SMD style, suitable for SMD mounting by flip -chip method. Connectors of the sensors come out to back side of the package. Both sides of the Sensors are ceramics (AlN). Face side is covered with black paint with high emissivity 0.95. Internal ambient of the Sensor is potted by a silicon compound of high temperature stability.
3.2 Preparations for working
You need to procure the following for working with the Sensors: - Mounting board with connectors to mount the Sensor in your setup. - Read-out device (i.e. RMT DX8140 Datalogger, millivoltmeter ), or third party read-out device. Note that the read-out device must have passive input for Sensor.
OPERATING MANUAL. HRX SERIES Page 9 of 32 - Device for Sensor self-calibration procedure. If RMT DX8140 Datalogger is procured , the procedure is available. Otherwise any model of RMT Z-meters is suitable for that.
3.3 Sensor testing
Before mounting the Sensor must be tested as described in Chapter 6.
3.4 Sensor calibration
If necessary, or required for an application the Sensor can be calibrated by the self-calibration procedure described in Chapter 10.
3.5 Mounting of the Sensor
The common mounting scheme in advised at Fig. 4.1 Fig 4.1 Schematic diagram of mounting and functionality of HRX Heat Flux Sensor . Ensure that the mounting surface is flat, dry, and free of dust and grease. Clean the Sensor surface with ethanol or isopropanol. Do not use acids or alkali for cleanin g the Sensor. Mount the Sensor onto circuit board . A detailed description of the Sensor mounting is given in Chapter 6.
THERMOELECTRIC HEAT FLUX SENSORS Page 10 of 32
3.6 Data acquisition
Connect the Sensor to the read-out devices and collect data according to the data acquisition procedure.
3.7 How to calculate heat flux
Every heat flux Sensor has performan ce parameter – sensitivity to heat flux (Sa and Se). The data acquisition device collects voltage output from the Sensor U. The heat flux P must be calculated as 𝑃 = 𝑈 𝑆𝑖 × 𝐹(𝑇) (4.1) Where Si – sensitivity: if Si=Se, P will be outputted in the units of heat flux density [W/m2]; if Si=Sa, the integral heat flux will be obtained in [W]; F(T) – temperature correction factor, dependence of sensitivity on working temperature T.
3.8 Sensors service
The service procedures and procedures of removing the Sensors from the setup are described in Chapter 11.
OPERATING MANUAL. HRX SERIES Page 11 of 32 4. HEAT FLUX SENSORS INTRODUCTION
4.1 Description of installation
The Sensor has two flat sides . Sides are different. Working side is completely black. Bottom side contains two connectors and marking between them. Fig. 4.1 HRX sensor top and bottom sides Fig. 4.1 Direction of heat flux.
THERMOELECTRIC HEAT FLUX SENSORS Page 12 of 32 5. FUNCTIONALITY TEST All HRX thermoelectric Heat Flux Sensors adhere to high manufacturing standards. Before shipping, the performance of each Heat Flux Sensor is individually checked and calibrated . All the data are advised in Specifications of the Sensor. However, external factors (e.g. transportation, prior use), may affect the functionality of the Sensor module. Before the permanent installation, the Sensor functionality must be tested.
5.1 Checking of AC Resistance
The electrical resistance testing is done using a standard multimeter via a four-wire probe measurement. The resistance measurement must be done without any applied temperature gradient (e.g. with th e Sensor hanging in air holding it at the cables). The resistance must be in the range specified in the Sensor’s respective datasheet. This value does not include the resistance of the cables. Resistance below 0.1 ohm indicates a short circuit, while resi stance higher than the value stated in the datasheet indicates physical wearout of the Sensor and/or its cables. In both cases, the Sensor is not functional and must be replaced. 5.2 Checking of Figure-of-Merit. The Sensor is a thermoelectric module device. Pe rformance and functionality of the Sensor can be examined by two parameters : the AC Resistance (see above) and Figure -of-Merit. In some cases functionality checking only by AC resistance measurements is not enough. Particularly in the case of probable failure, and necessity to investigate reasons of this. Checking of Z together with ACR gives much more information about functionality of the thermoelectric Sensor.
OPERATING MANUAL. HRX SERIES Page 13 of 32 Checking of the Figure -of-Merit require s a special device – Z-Meter. DX8140 Datalogger. It has special function of Figure-of-Merit checking. Contact RMT for the devices and checking. And visit RMT website for more literature on checking of Figure -of-Merit of thermoelectric modules - http://rmtltd.ru/technology/publications/. The Specification of every Sensor contains Z measured at vendor factory before shipment.
5.3 Checking of Sensor behavior
Connect the Sensor to a voltmeter (resolution preferably in the 0.1mV range). When touching the Sensor working side with a warm finger, you should get a signal in the mV range. A Sensor signal below 0.1 mV indicates a short circuit. Check whether the resistance of the Sensor is > 0.1 ohm as described above. If the signal randomly fluctuates between a positive and negative signal, or the voltage is in the +/- 1 V range, you may have an open circuit. Check the connection of your electrical probes. If the signal shows one of the three described features above, the Sensor is not functional and has to be replaced. In this case, please contact the vendor.
THERMOELECTRIC HEAT FLUX SENSORS Page 14 of 32 6. INSTALLATION OF SENSORS
6.1 Mounting circuit board
In order to obtain meaningful measurement data, the HRX Heat Flux Sensor has to be mounted with adequate mounting procedure. The sensor must be mounted onto circuit board. The recommended connectors drawing onto the board is given into the Sensor specification. Fig. 6.1 Recommended connectors onto circuit board for HRF02 - 040-03L04 sensor (the same is given in Specification for every model of HRX sensor).
6.2 Soldering profile
Recommended soldering profile is mentioned at Fig. 6.2
OPERATING MANUAL. HRX SERIES Page 15 of 32 Fig. 6.2 Soldering profile .
THERMOELECTRIC HEAT FLUX SENSORS Page 16 of 32 7. DATA ACQUISITION The HRX Heat Flux Sensors’ output is an analog voltage signal. Depending on the measurement task, the voltage signal can be in the μV to mV range. To read -out the Sensor signal, three options are available: the DX8140 Datalogger, a voltmeter, or a third party read -out device. The following section describes each option separately.
7.1 Datalogger DX8140
The DX8140 Datalogger is specifically developed for reliable and straightforward heat flux measurements in combination with the HRX and HRX Heat Flux Sensors. The DX8140 Datalogger works as a complete solution with included software. The DX8140 Datalogger can be set to measure either an analog voltage signal (in mV) or heat flux signal (in W/m2). Please follow the Instruction Manual, which is available for the DX8140 Datalogger. Applicability The DX8140 Datalogger is compatible with all HRX Heat Flux Sensors with a plug.
7.2 Voltmeter as a read-out device
Voltmeters are used for simple measurement tasks and/or for Sensor functionality tests. In order to read the output voltage of the Sensor with high accuracy, you need a voltmeter with high resolution. The resolution of the heat flux measurement is limited by the voltmeter resolution and noise. Table 1 demonstrates the relevance of voltmeter resolution. The voltmeter resolution is the most critical feature when choosing the optimal device. Due to the low electrical resistance of the Sensor, there are no spec ial requirements regarding the input resistance of the voltmeter.
OPERATING MANUAL. HRX SERIES Page 17 of 32 Table 8.1: Heat flux resolution of heat flux Sensors of HRX series at different voltmeter resolution (1 mV and 1 V) Sensor type Sensitivity, mV/(W/m2) Heat flux resolution W/m2 Voltmeter 1mV VoltmeterV HRD02-040-03L04 11 91 0,091 HRD02-040-05L04 18 56 0,056 HRD03-040-05L06 18 56 0,056 Applicability Voltmeters are compatible with all the HRX Heat Flux Sensors.
7.3 Third party read-out device
A data logger is highly recommended for the measurement of time - dependent variations of the Sensor signal. For the choice of a suitable device, apply the same considerations as for the voltmeter. Applicability Third party read -out devices are compatible with all the HRX Heat Flux Sensors without a plug.
THERMOELECTRIC HEAT FLUX SENSORS Page 18 of 32 8. DATA ANALYSIS This section contains the basic analysis methods needed to interpret data from the HRX and HRX Heat Flux Sensors. All the information necessary for it can be found in the following documents: - Specifications. The Specification is delivered with every Heat Flux Sensor for R&D Applications. It contains the Sensor sensitivity Se0 [V/(W/m2)] and integral sensitivity Sa 0 [V/W] at calibration “standard” temperature T 0, and all correction factors that are needed to increase accuracy of the results. - Datasheet. The datasheet provides an overview for all technical parameters of HRX and HRX Heat Flux Sensor. It also states the Sensor area, which is necessary for calculating heat flux.
8.1 Temperature corrections
The sensitivity of the thermoelectric Heat Flux Sensors depends on the temperature at which they are used. For thermoelectric Heat Flux Sensors of the HRX series averaged temperature dependence of 0.2 5%/°C is given in the Specifications and Datasheets (Table 9.1). The standard calibrated Sensitivity is given in the specification at temperature 300K (27°C) which is selected as “standard”. Thus, if us ing the Sensors at tempera tures below or above 300K (27°C), with every degree of Centigrade accuracy becomes worse by 0.2% per degree. For temperature range close to the “standard” temperature, i.e. +/-1 °C, the inaccuracy of the measurements in the general case is negligible – about ±1%. But for a wider range of temperatures and for precise measurements the temperature corrections are recommended.
OPERATING MANUAL. HRX SERIES Page 19 of 32 It is easy to obtain them as for all thermoelectric Heat flux Sensors of RMT the temperature dependences are investiga ted and general formulas are advised in the Specifications and Datasheets. The temperature dependence of sensitivity is given as a polynomial of the 3-rd order: where 𝐴0- is always =1; 𝑆𝑎0 - sensitivity at “standard” calibration temperature 𝑇0 (= 300𝐾); 𝑆𝑎 – sensitivity at working temperature 𝑇. In the expression (9.1) value in brackets is a temperature correction factor. Sensitivity Se [mV/(W /m2)] is also given in the Sensor Specification (Chapter 3. Specifications) and it correlates with the integral sensitivity Sa [V/W] as 𝑆𝑒 = 𝑆𝑎 × 𝑆 (9.3) where 𝑆 – sensitive surface of the heat flux Sensor. Thus the temperature correction factor 𝐹(𝑇) is the same for both sensitivities 𝑆𝑎 = 𝑆𝑎0 × 𝐹(𝑇) (9.4) 𝑆𝑒 = 𝑆𝑒0 × 𝐹(𝑇) (9.5) The coefficients of the polynomial expression are common and are given in the Datasheet of the heat flux Sensor series (Table 9.1). Table 9.1. Polynomial expression of temperature dependence of Sensors sensitivity
THERMOELECTRIC HEAT FLUX SENSORS Page 20 of 32 Sensor series A0 A1 A2 dS/dT, % Ta, K HTX 1 1,937E-03 -1,634E-05 0,20 300 HRX 1 2,299E-03 -2,094 E-05 0,25 300 HRX 1 2,299E-03 -2,094 E-05 0,25 300 Temperature range of calibration -40…+80 °С Common formula Thus, to obtain the temperature correction , you need to know average temperature T of measurement. You need to apply an external temperature Sensor. If T is not measured, it can be approximated by the following formula: 𝑇 = 𝑇ℎ + 𝑇𝑐 2 (9.6) where Th and Tc are the respective temperatures of the hot (working) side and the cold (bottom – circuit board) side of the Sensor. Typically, the difference between Th and Tc is small. If the Sensor is mounted onto the circuiting board, T is better approximated by T = Th. Example for calculating The Sensor type HRD02-040-02L04 was taken for measurements. The Sensor is mounted on a circuit board and is exposed to air. The surface has a temperature of 35°C, which is a good approximation for T (see the last section). The following Sensor parameters are given in its specification (Chapter 3. Specifications): Se = 11 μV/(W/m2) Sa = 0.68 V/W dS/dT=0.25%/°C
OPERATING MANUAL. HRX SERIES Page 21 of 32 To = 27°C The temperature correction factors are the following: - With use of averaged dS/dT (=0.20%/°C) 𝐹(𝑇) = 1 + ∂S = 1,058 (9.7) - More precise correction by polynomial expression (9.2) with given coefficients (table 9.1) gives the following: (9.8) The polynomial expression gives a more precise correction factor which is slightly differing from the rough averaged value. Thus, if possible, we recommend using the Polynomial expression rather than an averaged value given in the Specification only as a indicator value. But for rough estimations the averaged value ∂T is quite enough.
8.2 Heat flux measurements
The DX8140 Datalogger, a voltmeter, or a third party read -out device measures and store s (Datalogger) an analog output in voltage units U (V, mV, V) . The heat flux P is calculated with use of sensitivity and calculated correction factor ( the above section) F(T). De pending on the sensitivity units V/(W/m2) ( Se) or V/W ( Sa) the density of heat flux W/m 2 (Ps) or total heat flux W (Pa) will be calculated as 𝑃𝑒 = 𝑈 𝑆𝑒 × 𝐹(𝑇) (9.9) 𝑃𝑎 = 𝑈 𝑆𝑎 × 𝐹(𝑇) (9.10)
THERMOELECTRIC HEAT FLUX SENSORS Page 22 of 32 Example for heat flux measurement The same Sensor type HRD02-040-03L04 (the above section) at the temperature 35°C with a given sensitivity and calculated correction factor (9.6) measures the following: Voltage U = 570 μV Heat flux is the following 𝑃𝑒 = 𝑈 𝑆𝑒 × 𝐹(𝑇) = 570 𝑃𝑎 = 𝑈 0.68 × 1,017 = 0.824 × 10−6𝑊 = 0.824 𝑚𝑊 (9.12)
OPERATING MANUAL. HRX SERIES Page 23 of 32 9. SELF-CALIBRATION PROCEDURE
9.1 Method
Sensitivity of thermoelectric Heat flux Sensor Sa: 𝑆𝑎 = 𝑈 𝑃𝑎 where U – Sensor signal at total heat flux Pa; N – number of thermoelement pairs in the Sensor; S – sensitive surface area; RT – thermal resistance of Sensor ; – averaged Seebeck coefficient for pair of n- and p-type thermoelements. Figure-of Merit Z of thermoelectric Sensor 𝑍 = (𝑁 × 𝑎)2 × 𝑅𝑇 𝐴𝐶𝑅 (10.2) where ACR – AC resistance of the heat fux Sensor. The c alibration expression with use of Z, ACR and Seebeck coefficient are the following 𝑆𝑎 = 1 𝑎 × 𝑁 𝑍 × 𝐴𝐶𝑅 (10.3) 𝑆𝑒 = 𝑆𝑎 × 𝑆 = S 𝑎 × 𝑁 𝑍 × 𝐴𝐶𝑅 (10.4) where S – sensitive surface area. Thus, according to the formulas (10.3 -10.4) the sensitivity calibration of the thermoelectric heat flux Sensor is available with use: - Construction parameters of the Sensor: number of pellets pairs N; and size of sensitive surface S. The parameters are give n in datasheets and Specifications (Chapter 3. Specifications);
THERMOELECTRIC HEAT FLUX SENSORS Page 24 of 32 - Property of thermoelectric material of the Sensor (Seebeck coefficient). This parameter measured at standard temperature is given in the Sensor Specification. Moreover , temperature dependence of the parameter is also given in Specifications and datasheets (Table 10.1). - Measurement of Figure -of-Merit Z and AC Resistance ACR of the Sensor. The measurements can be done with use of DX8140 Datalogger or Z-meters of RMT, any model. That is really a self-calibration method as it does not require any external heat source. And can be done at the user setup. Table 10.1 Averaged (for pair of n- and p-types pellets) Seebeck coefficient of thermoelectric Sensors Typical a0, мкВ/К A0 A1 A2 A3 T0, K 410 1 +1,291E-03 -8,647-06 +7,843E-08 300 Temperature range -40…+80 °С Common formula
9.2 Measurement Scheme
The self -calibration is made by measurement of Figure-of-Merit and ACR resistance of thermoelectric heat flux Sensor by the four-wire method which is provided by four wires of the FET cable connected to the Sensor. Fig. 10.1 Connection scheme for self -calibration procedure. U I HR
OPERATING MANUAL. HRX SERIES Page 25 of 32
9.3 Equipment
Use the series of Z -Meters made by RMT for measurement of Figure -of- Merit and ACR resistance of thermoelectric heat flux Sensor. You can also use the Datalogger DX8140 series developed for the HRX series of heat flux Sensors.
9.4 Example
Heat Flux Sensor type HFD02-040-04L04 was obtained with Specification where were listed the following: Dimensions - 4x4 mm2 Number of pellet pairs - 40 Seebeck coefficient, - 420 (at 300K), V/K Measurements of thermoelectric performance parameters according to scheme at Fig 10.1 with use of Z -Meter DX4090 (http://rmtltd.ru/products/devices/testers/zmeters/) gives the following: Figure-of-Merit , Z - 1.92x10-3 K-1 ACR - 5.94 Ohm Both are referred to T0=300K. According to formulas (10.3) and (10.4) 𝑆𝑎 = 1 𝑎 × 𝑁 𝑍 × 𝐴𝐶𝑅 = 1.92 × 10−3 × 5.94 420 × 10−6 × 40 = 0.679 𝑉/𝑊 𝑆𝑒 = 𝑆𝑎 × 𝑆 = 0.679 × 42 × 10−6 = 10.9 𝜇𝑉/𝑊 The c alibration results are close to the Sensor standard Specification (Chapter 2).
THERMOELECTRIC HEAT FLUX SENSORS Page 26 of 32 10. MAINTENANCE OF THE SENSOR
10.1 Removing Sensor from measurement setup
The sensors of HRX series soldered to circuit board can be de-soldered.
10.2 Cleaning of Sensor
Cleaning is only necessary before mounting the Sensor. Clean the Sensor surface with ethanol or isopropanol. Once the Sensor is mounted, no further cleaning is necessary.
10.3 Storage
Store an unused HRX Heat Flux Sensor at ambient temperature in a clean and dry place. No further care is required.
OPERATING MANUAL. HRX SERIES Page 27 of 32 11. ADDITIONAL INFORMATION
11.1 Electromagnetic field
Due to the very low electrical resistance of the Sensor the output signal is resistant to electromagnetic interference. In most cases, no countermeasures are necessary. If electromagnetic interference is a problem, typical countermeasures (e.g. shielded cables, grounding) have to be taken.
11.2 Application in temperatures outside of calibration range
The calibration temperature range of the HRX Heat Flux Sensors is stated in the respective data sheets. Within this temperature range, RMT guarantees a relative error less than +/- 3%. Outside of this range, the relative error may exceed this value.
11.3 Use in fluids
The Sensor is hermetically sealed and may be exposed to moisture or clean neutral water at temperatures less than 100° C for a short time by properly insulating all electrical parts. However, long term exposure to wet ambient conditions is not recommended as this may corrode the metallic leads. Use in other fluids is not recommended. In any case, do not expose the Sensor to strong acids or bases.
THERMOELECTRIC HEAT FLUX SENSORS Page 28 of 32 12. DEFINITIONS Value Units Name 𝑃𝑒 W/m2 Heat flux density 𝑃𝑎 W Integral (total) heat flux to Sensor 𝑆𝑒 V/(W/m2) Sensitivity of heat flux Sensor 𝑆𝑎 V/W Integral sensitivity 𝐷∗ cmHz1/2/W Detectivity NEP W/Hz1/2 Noise equivalent power 𝑅𝑇 K/W or K/(W/m2) Thermal resistance 𝛼 V/K Seebeck coefficient 𝐴𝐶𝑅 Ohm AC resistance of Sensor 𝑁 Number of pellets (thermoelements) pairs ∆𝑇 K Operation temperature difference 𝑇ℎ K Hot side temperature 𝑇𝑐 K Cold side temperature 𝐾𝑇 W/K Thermal conductance 𝑘 W/mK Thermal conductivity 𝑠 mm2 Cross-section of pellet ℎ mm Height of pellet H mm Sensor thickness AxB mm2 Sensor size (or diameter if “Dia”) s Thermal time constant Z K-1 Thermoelectric Figure-of-Merit Emissivity of sensitive surface
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THERMOELECTRIC HEAT FLUX SENSORS Page 32 of 32 RMT Ltd. phones: +7-499-678-20-82 e-mail: info@rmtltd.ru www.rmtltd.ru