PASCO Specialty & Mfg. PS-2148 User's Manual
Contents
1. How is the temperature of an object or the temperature difference between the object and the sensor related to the net intensity Cooling Measure the temperature of a hot object as it cools and measure the radiation intensity emitted by it How does the rate of temperature change compare to the total radiated power How does the total temperature change compare to the total radiated energy Besides radiation what are the other mechanisms of heat loss ACC 7 IR Sensor Intensity vs Emissivity Using the TD 8580 Thermal Cavity measure the radiation intensity emitted by different surfaces at the same temperature How do the color and texture of surfaces affect the radiated intensity Compare the intensity from a surface to the intensity from a cavity of the same temperature Radiated Power vs Input Power of a Light Bulb Measure the voltage and current applied to a small light bulb and the radiation intensity emitted by it Calculate the input electrical power and the total radiated power How do they compare Second Law of Thermodynamics The second law of thermodynamics states that heat tends to flow from a hotter object to a cooler object The objects do not have to be in contact for this to occur because heat can be transferred through radiation Measure the net radiation intensity of an object that is cooler than the sensor In what direction is energy flowing Allow the cool object and the sensor to come to the sa2. etched in silicon At Pair of Thermocouples Thermopile IR Sensor Usage Notes Field of View 929 There are two simple arrangements TT of source object and sensor In the first the source approximates an infinite plane The radiation propagates rom the source asa plane wave and the intensity does not increase with increasing distance from the source In this arrangement the radiated power incident on the active area of the sensor is equal to the power emitted Usage Notes by an equivalent area of the source A plane source should fill the 92 field of view This approximation 1S most accurate A point source should be within the 48 field when the source fills the entire 92 field of view of the sensor The other simple arrangement is one where the source approximates a point In this case the intensity of radiation emitted by the source obeys the inverse square law The point source should be within the 48 field of view so that it illuminates the entire active area Ideally the source should be directly in front of the sensor so that the radiation is normal to the window and to the active area Other sources of radiation that you wish to ignore should be outside of the 92 field of view The Aperture Bracket OS 8534 can be used to further limit the field of view Power and Intensity The sensor measures net intensity which is net power divided by the active area of the detector The formula for
3. gt Instruction Manual pasforl No 012 08852A IR Sensor PS 2148 IR Sensor Sensor Handle Shutter Thumbscrew amp Washer Included Equipment Part Number IR Sensor PS 2148 Shutter with thumbscrew and washer 003 08860 Sensor Handle Cl 9874 4 pack Additional Equipment Required PASPORT interface See PASCO catalog or www pasco com DataStudio or DataStudio Lite See PASCO catalog or www pasco com required for computer based data collection DS Lite available for free download Additional Equipment Recommended PASPORT Extension Cord PS 2500 Aperture Bracket OS 8534 Thermal Cavity TD 8580 Introduction The PASPORT IR Sensor measures infrared radiation intensity over a broad spectrum allowing students to study a variety of phenomena including blackbody radiation the Stefan Boltzmann law heat flow by radiation solar radiance and non contact temperature measurement better o J oy Toy e 8 10101 Foothills Bivd e Roseville CA 95747 7100 Phone 916 786 3800 FAX 916 786 8905 e www pasco com IR Sensor Sensor Setup The sensor s silicon based thermopile encapsulated in nitrogen with a thallium bromide iodide KRS 5 window has a flat spectral response from 0 7 to 30 um It measures radiation intensity up to 4500 W m An integrated thermistor measures the temperature of the detector allowing the user to calculate detector emitted radiation In conjunction with a PASPORT interface the IR Sensor measur
4. through the thermopile which sets up a temperature different AT across the thermopile The thermopile produces a voltage V that is proportional to AT If the sensor is warmer than the target source then net power flows out of the sensor and AT and V are negative The net radiated power P is proportional the power flow through the thermopile which is proportional to AT which in turn is proportional to V therefore V is proportional to P V RP The constant R is known as the responsivity of the detector For the PS 2148 sensor amp is about 31 V W The sensor amplifies the voltage produced by the thermopile and converts it into a digital signal A microprocessor in the sensor calculates intensity which is incident power divided by the area of the detector 2 25 mm The thermopile voltage and intensity data are sent digitally to the PASPORT interface or computer iz Kile Background Ts Source e T Thermopile v What is a thermopile A thermopile is a series of thermocouples A thermocouple is the junction of two different metals When two thermocouples are connected in series and are at different temperatures a voltage proportional to the temperature difference occurs between them This voltage is usually very small Ina thermopile many thermocouples are connected in series as shown below to produce a larger voltage The thermopile in the PS 2148 consists of 120 junctions
5. V k T T Where k is a constant that you will determined empirically using an object of known temperature You must also know the temperature of the active area of the detector T The embedded thermistor does not measure T directly rather it measures the temperature of the opposite side of the thermopile T AT However since AT is always much less than T measured in Kelvin the thermistor temperature is a good approximation of T The constant k depends on several factors unique to each measurement setup including the properties of the particular sensor used deviation of the target surface from an ideal blackbody and any intervening medium such as air For more accurate results the value of k should be empirically determined with an object of known temperature that is similar to the objects of unknown temperature that you intend to measure For the temperature calibration procedure you will need an object of variable temperature of which you can make a direct temperature measurement A cup of hot water is a convenient object Ideally it should have a matte surface so that its emissivity is close to 1 You will also need a temperature sensor to measure the temperature directly The PASCO Fast response Probe PS 2135 works well because it responds quickly to small changes Use the probe with a PS 23125 Temperature sensor or any other PASPORT sensor that supports external probes or connect the probe directly to the temperatur
6. bject of unknown temperature T is the calculated temperature of the object Usage Notes T is the temperature measured by the temperature probe T is the temperature measured by the IR sensor s internal thermistor For information on setting up graphs linear fits and calculations refer to the DataStudio Help menu or the Xplorer GLX Users Guide ey Actual source temperature top detector temperature middle and voltage bottom vs time as ice is added to hot water PAS C Model No PS 2148 Suggested Activities m i Slope 3 T BBE 8 2 9E 6 bi Y Intercept 4 02E 8 1 BEYT r 0 998 Mean Squared Error 2 00E 16 FEE Root MSE 1 42E 6 5 Voltaged mv 4 T 4 T versus voltage Suggested Activities Solar Radiation Measure the radiation intensity from the sun Compare it to the intensity from a different part of the sky When measuring the temperature of the sky make sure that the sun and other objects such as trees and buildings are not in the field of view How does the presence of clouds or the angle of the sun in the sky affect solar radiation intensity According to your measurement of intensity what is the total power radiated by the sun What is its surface temperature Intensity vs Distance Graph intensity as a function of distance How does a point source such as the filament of a small light bulb compare to a larger source such as a hotplate Intensity vs Temperature
7. d all local safety guidelines that apply to you IR Sensor Technical Support For assistance with any PASCO product contact PASCO at Address PASCO scientific 10101 Foothills Blvd Roseville CA 95747 7100 Phone 916 786 3800 800 772 8700 Fax 916 786 3292 Web www pasco com Email techsupp pasco com Limited Warranty For a description of the product warranty see the PASCO catalog Copyright Notice The PASCO scientific 012 08852A IR Sensor Instruction Manual 1s copyrighted with all rights reserved Permission 1s granted to non profit educational institutions for reproduction of any part of this manual providing the reproductions are used only in their laboratories and classrooms and are not sold for profit Reproduction under any other circumstances without the written consent of PASCO scientific is prohibited Author Alec Ogston better o 1 oy Toy e 8 10101 Foothills Bivd e Roseville CA 95747 7100 Phone 916 786 3800 FAX 916 786 8905 e www pasco com better o 1 oy Toy e 8 10101 Foothills Bivd e Roseville CA 95747 7100 Phone 916 786 3800 FAX 916 786 8905 e www pasco com
8. e port of the Xplorer GLX interface Place the IR sensor close to the cup but not touching so that the surface of the cup fills the sensor s entire field of view In this way the surface 1s seen as an infinite plane and the distance between the object iz Kile Usage Notes To make the detector temperature visible in DataStudio go the Experiment Setup window and select Temperature with units of K This measurement is the temperature of the detector Do not confuse it with the temperature of the target object IR Sensor and the sensor is irrelevant Place the end of the fast response temperature probe in the cup close to the side that the IR sensor is viewing Set A Vu computer or interface to calculate T 4 and to graph T T versus thermopile voltage Pour hot water about 709 C into the cup Leave some room for ice but make sure that the water surface is above the sensor s field of view Start data collection After a few seconds add a piece of ice to the cup and stir gently Continue to add ice one piece at a time while stirring until the temperature has decreased by 20 K or more Stop data collection Apply a linear fit to the graph of T TA versus voltage The slope of the best fit line equals k Using this value of k create a calculation of the form T k V Td 4 1 4 Where V is the thermopile voltage and Td is the detector temperature Take IR data for an o
9. es and records thermopile voltage radiation intensity and detector temperature at up to 100 samples per second Sensor Setup Connect the IR sensor to a PASPORT interface either directly or via a PASPORT extension cord If you are using a computer connect the interface to the USB port and start DataStudio By default the sampling rate of the sensor is 100 Hz To change it go to the Experiment Setup window in DataStudio or the Sensors screen of the Xplorer GLX To set up the sensor for estimating the temperature of objects see Non contact Temperature Sensor Simulation on page 5 If desired connect the sensor handle to the 14 20 threaded connector on the sensor This connector can also be used with any other 14 20 screw It is not always necessary to attach the shutter but it can be useful to i Sensor Handle control the detector temperature Install the shutter as shown using the and Shutter included thumbscrew and washer Or use the sensor handle in place of ERO B the thumbscrew To measure net IR intensity point the sensor at a surface or object such as your hand or the sun and start data collection in DataStudio or the PASPORT interface In DataStudio intensity is automatically shown in a digits display In DataStudio or on the Xplorer GLX the data can also be displayed in a graph table or meter Refer to the DataStudio Help menu or the Xplorer GLX Users Guide for information on B ac kg roun d set
10. me temperature What happens to the energy flow Further Reading At www dexterresearch com follow the Technical Briefs link for further information on thermopile detectors and radiometery KRS 5 Window Transmittance Transmittance 100 Further Reading PASCO part EM 8627 is a pack of 25 light bulbs that work well for this experiment They can be used with Light Bulb Sockets EM 8630 10 pack and a power supply capable of 300 mA at 2 V The PASPORT Voltage Current Sensor PS 2115 can be used to measure the electrical power supplied to the bulb 90 80 70 60 50 40 30 20 1 2 3 4 5 6 7 8 9 10 2 0 3 0 4 0 5 0 10 20 Wavelength um 30 40 50 100 Iz Kime Model No PS 2148 Specifications Active Area 1 5 x 1 5 mm Size Element Area 2 25 mm Number of 120 Thermocouple Junctions Field of View 48 or 92 see Field of View on page 4 for description Intensity 500 to 4500 W m max mange 0 to 1000 W m linear Spectral flat from 0 7 to 30 um response Window KRS 5 see transmittance Material graph on page 8 Encapsulating nitrogen Gas Responsivity 31 7 V W Safety Read the instructions before using this product Students should be supervised by their instructors When using this product follow the instructions in this manual an
11. net power is P I A where I is the measured net intensity and A 2 25 mm is the detector area The net power equals the incident power from all external sources P a minus the power radiated by the detector P P 4 A GT The temperature of the detector T is measured by in integrated thermistor Detector Temperature Control Every time you place the sensor near a hot object the detector will begin to heat up and it will cool when you move it away If you wish to make several intensity measurements at a constant detector Interfering sources should be outside of the 92 field To make the detector temperature visible in DataStudio go the Experiment Setup window and select Temperature with units of K On the Xplorer GLX go to the Sensors screen PAS C Model No PS 2148 temperature allow the detector to cool between each measurement by moving it away from all hot objects Then place the sensor near the object to be measured and monitor the detector temperature as it increases Record the intensity when the detector temperature reaches a certain value Alternatively you can mount the shutter on the sensor and control the temperature by opening and closing it Non contact Temperature Sensor Simulation Based on data collected by the IR sensor and a calibration constant you can calculate the temperature of an object If the target object approximates a blackbody then the voltage of the thermopile is
12. ting up data displays IR Radiation All objects emit IR radiation The radiated power per unit area of an object is given by the Stefan Boltzmann law I soT Where T is the objects absolute surface temperature and o is the Stefan Boltzmann constant equal to 5 670 x 10 W m K The emissivity is a property of the object s surface and can range from 0 to 1 An object with 1 is described as a blackbody PAS C Model No PS 2148 Theory of Operation Consider a blackbody of temperature T whose shape can be approximated as an infinite plane and a flat detector surface parallel to source with area A Because radiation from an infinite plane propagates as a plane wave the power flow from the source to the detector P equals the radiation emitted by a part of the source whose area is equal to the detector s area regardless of the distance between the source and detector P A oT The detector itself also radiates in accordance to the Stefan Boltzmann law If the detector s temperature is T then power radiating out of the detector 1s P A oT Therefore the net power absorbed by the detector is P A oTt T The net intensity which is what the sensor measures is the net power divided by the detector area The net power that flows onto the active detector area by radiation P Pa flows out of the detector by conduction to other parts of the sensor A proportion of that power is conducted
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