Heat Flux Sensors
EKO Heat Flow Sensors are applied to measure the heat flow or thermal conductivity in materials and radiative IR flux emitted by body surfaces. The sensors are suitable for indoors applications, some models made for outdoors purposes and are available in different sizes and thickness. All sensors are extremely flat, which is a big advantage considering the minimum interference with the conditions of the testing area the thermal dynamics. Since sensor foils are relatively flexible those can easy be applied on curved surfaces and can be used in different applications to measure the performance of insulating materials in refrigerators, container walls, pipes, building constructions, etc.
A heatflux sensor is a thermopile sensor which generates an electric voltage proportional to the ∆T across the thermocouple hot and cold junctions. To generate a measurable voltage heat flux sensors have multiple thermocouples spread over the total area connected in series. EKO heatflux sensor have a vertical thermocouple built up which means that all cold junctions and hot junctions are separated by the surface top and bottom side.
Energy flux can be measured in both directions, where the sensor will simply give a positive or negative voltage. The thermal conductivity measurement unit (W/m/K) is defined as the energy (W) needed to create a thermal potential (∆T) of 1 Kelvin (K) through a thermal conductor of a specific length (m). The radiative flux (W/m2) is defined as the energy (W) radiated or absorbed as a unit of surface area (m2). When the sensor is put at the top of a surface the thermal conductivity, thermal transmission, radiation and convection component are measured. When the sensor is placed in between to surfaces inside the object it measures the thermal transmission by means of thermal conduction. The heat flow (thermal conductivity) through the sensor is proportional to the inverse thermal resistance (1/R) multiplied by the temperature across the sensor (∆T).
|Operating temperature range (°C)||-30°C ~ +120°C||-30°C ~ +120°C||-20°C ~ +120°C||-20°C ~ +120°C|
|Sensitivity constant (mV/W/m²)||0.028||0.025||0.20||0.006|
|Temperature dependency (%/°C)||-0.03||-0.03||<0.05|
150 - 550
150 - 550
600 - 900
15 - 30
|Reproducibility (%)||+/- 2%||+/- 2%||+/- 2%||+/- 2%|
|Size (L x W x T, mm)||42 x 20 x 0.9||50 x 25 x 1.2||310 x 310 x 0.7||50 x 50 x 0.7|
|Substrate||Teflon||Teflon||Glass Epoxy||Glass Epoxy|
|Remarks||All-purpose, small size, high sensitivity||Water-proof, highly durable, robust||Large size and very thin and flexible, low heat resistance||Very thin and flexible, low heat resistance|
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Calibration Procedure & Traceability
All heatflux sensors are calibrated relatively to a standard heat flow sensor which was calibrated at EKO isntruments with an absolute calibrater.
The Heat Flow Sensors are calibrated according to the Guarded Hot Plate Method which is a absolute thermal conductivity measurement method for insulators and complies with JIS A 1412. By measuring the voltage and applied power to the main hot plate, the heat flow which flow though the sample can be calculated taking into account the thermal conductivity from the sample temperature difference and thickness.
Changes in sensitivity is very small (<0.3%/1 year) if the heat flow sensor is used in normal application (temperature range, setup environment, etc.). Therefore, the recommended recalibration should be 3~5 years after the delivery.
Frequently Asked Questions
If a heat flux sensor does not make good thermal contact with the material to be measured, it will cause a local hot spot to form (or a cold spot in the case where the heat flux is ...
How to measure the low output voltage of a heat flow sensor? In order to measure the output Voltage (µV - mV) , the measurement equipment should have a mV input rage ...