1、Designation: E2758 10Standard Guide forSelection and Use of Wideband, Low Temperature InfraredThermometers1This standard is issued under the fixed designation E2758; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers electronic instruments intended formeasurement of temperature by detecting intensity of thermalradiation
3、exchanged between the subject of measurement andthe sensor.1.2 The devices covered by this guide are referred to as IRthermometers.1.3 The IR thermometers covered in this guide are instru-ments that are intended to measure temperatures below 1000C and measure a wide band of thermal radiation in the
4、infraredregion.1.4 This guide covers best practice in using IR thermom-eters. It addresses concerns that will help the user make bettermeasurements. It also provides graphical tables to help deter-mine the accuracy of measurements.1.5 Details on the design and construction of IR thermom-eters are no
5、t covered in this guide.1.6 This guide does not cover medium- and high-temperature IR thermometry (above 1000 C). It does notaddress the use of narrowband IR thermometers.1.7 The values of quantities stated in SI units are to beregarded as the standard. The values of quantities in parenthe-ses are n
6、ot in SI and are optional.1.8 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations pr
7、ior to use.2. Referenced Documents2.1 ASTM Standards:2E1256 Test Methods for Radiation Thermometers (SingleWaveband Type)E1862 Test Methods for Measuring and Compensating forReflected Temperature Using Infrared Imaging Radiom-etersE1897 Test Methods for Measuring and Compensating forTransmittance of
8、 an Attenuating Medium Using InfraredImaging RadiometersE1933 Test Methods for Measuring and Compensating forEmissivity Using Infrared Imaging Radiometers2.2 IEC Standards:IEC 62942-1 TS Industrial process control devicesRadiation thermometersPart 1: Technical data for radia-tion thermometers3. Term
9、inology3.1 Definitions:3.1.1 absolute zero, na temperature of 0 K (-273.15 C).3.1.2 atmospheric attenuation, na ratio showing howmuch thermal radiation in a given spectral range is absorbed orscattered in air over a given distance.3.1.3 atmospheric transmission, na ratio showing howwell thermal radi
10、ation in a given spectral range at a givendistance travels through a certain distance of air.3.1.4 attenuating medium, na semi-transparent solid, liq-uid or gas, such as a window, filter, external optics and/or anatmosphere that reduces thermal radiation.3.1.5 background radiationsee reflected radia
11、tion.3.1.6 blackbody, nthe perfect or ideal source of thermalradiant power having a spectral distribution described byPlancks Law.3.1.7 blackbody simulator, na device with an emissivityclose to unity that can be heated or cooled to a stabletemperature.3.1.8 calibration adjustment, nthe correction to
12、 an IRthermometer based on its calibration.3.1.9 center wavelength, nthe simple average of the lowerand upper spectral range limits.3.1.10 celestial radiation, nflux coming from the sky.3.1.11 contact thermometer, nan instrument that isadapted for measuring temperature by means of thermalconductance
13、 by determining the temperature at the momentwhen negligible thermal energy flows between the thermom-eter and the object of measurement.1This guide is under the jurisdiction of ASTM Committee E20 on TemperatureMeasurement and is the direct responsibility of Subcommittee E20.02 on RadiationThermomet
14、ry.Current edition approved May 1, 2010. Published June 2010. DOI:10.1520/E2758 - 10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary
15、page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.12 dew point, nthe temperature at which water vaporcondenses into liquid water.3.1.13 diffuse reflector, na surface that produces a diffuseimage of a reflect
16、ed source.3.1.14 distance ratio, nthe ratio of the measuring distanceto the diameter of the field-of-view, when the target is in focus.3.1.15 electromagnetic radiation, nphysically occurringradiant flux classified according to wavelength or frequency.3.1.16 emissivity (e), nthe emissivity of a surfa
17、ce is theratio between the radiation emitted from this surface and theradiation from a blackbody at the same temperature.3.1.16.1 DiscussionThe emissivity describes a thermo-physical material characteristic, which in addition to thechemical composition of the material may also be dependenton the sur
18、face structure (rough, smooth), the emission directionas well as on the observed wavelength and the temperature ofthe measured object.3.1.17 emissivity setting, nan adjustment on an IR ther-mometer to compensate for an emissivity of non-unity.3.1.17.1 DiscussionIn most measuring situations a radia-t
19、ion thermometer is used on a surface with an emissivitysignificantly lower than one. For this purpose most thermom-eters have the possibility of adjusting the emissivity setting.The temperature reading is then automatically corrected.3.1.18 emissivity tables, na list of objects and theirmeasured emi
20、ssivity for a particular IR thermometer.3.1.19 field-of-view (FOV), na usually circular, flat sur-face of a measured object from which the radiation thermom-eter receives radiation.3.1.20 frost point, nthe temperature at which water vaporcondenses into solid water or ice.3.1.21 infrared (IR), adjref
21、erring to electromagnetic ra-diation with a wavelength from approximately 0.7 to 30 m.3.1.22 infrared reflector, na material with a reflectance inthe infrared region as close as possible to unity.3.1.23 infrared sensing device, none of a wide class ofinstruments used to display or record or both inf
22、ormationrelated to the thermal radiation received from any objectsurfaces viewed by the instrument.3.1.24 infrared (IR) thermometer, noptoelectronic instru-ment adapted for noncontact measurement of temperature of asubject by utilizing thermal radiation exchange between thesubject and the sensor.3.1
23、.24.1 DiscussionIR thermometers are a subset of ra-diation thermometers. Most manufacturers use the term IRthermometer for handheld radiation thermometers. In general,these devices are wideband and use a thermopile detector.3.1.25 IR thermometry, nthe use of IR thermometers todetermine temperature b
24、y measuring thermal radiation.3.1.26 irradiance (E), nthe radiant flux (power) per unitarea incident on a given surface in units of W/m2.3.1.27 limit of error, nthe extreme value of measurementerror of an infrared thermometer reading, relative to referencetemperature standards, as permitted by a spe
25、cification.3.1.27.1 DiscussionManufacturers sometimes use theterm accuracy in their specifications to represent limit of error.3.1.27.2 DiscussionA manufacturers accuracy specifica-tion may apply only to well defined conditions.3.1.28 low-temperature, adjfor radiation and IR ther-mometry, referring
26、to any temperature below 660 C.3.1.29 measurement uncertainty (accuracy), nparameter,associated with the result of a measurement, that characterizesthe dispersion of the values that could reasonably be attributedto the measurand .3.1.30 measuring distance, ndistance or distance rangebetween the radi
27、ation thermometer and the target (measuredobject) for which the radiation thermometer is designed.3.1.31 measuring temperature range, ntemperature rangefor which the radiation thermometer is designed.3.1.32 noise equivalent temperature difference (NETD),nparameter which indicates the contribution of
28、 the measure-ment uncertainty in C, which is due to instrument noise.3.1.33 opaque, adjreferring to the property of a materialwhose transmittance is zero for a given spectral range.3.1.34 operating temperature range and air humidity range,nthe permissible temperature range and humidity rangewithin w
29、hich the radiation thermometer may be operated. Forthis temperature range and humidity range the specificationsare valid.3.1.35 radiance (L), nthe flux per unit projected area perunit solid angle leaving a source or, in general, any referencesurface.3.1.35.1 DiscussionIf 2F is the flux emitted into
30、a solidangle v by a source element of projected area Acos(u), theradiance is defined as:L 52FvAcosu!where:u = the angle between the outward surface normal of thearea element A and the direction of observation (unit =W/srm2).3.1.36 radiant power density (M), nthe radiant flux perunit area leaving a s
31、urface that is,M 5FAwhere:F = flux leaving a surface element A (unit = W/m2).3.1.37 reflectance, nthe ratio of the radiant flux reflectedfrom a surface to that incident upon it.3.1.38 reflected radiation, nthe thermal radiation incidentupon and reflected from the measurement surface of thespecimen.3
32、.1.39 reflected temperature, nthe temperature of theradiant flux incident upon and reflected from the measurementsurface of a specimen.3.1.40 sensor, ndevice designed to respond to IR radia-tion and convert that response into electrical signals.3.1.41 size-of-source effect, nThe difference in therad
33、iance- or temperature reading of the radiation thermometerwhen changing the size of the radiating area of the observedsource.3.1.42 spectral range, nparameter which gives the lowerand upper limits of the wavelength range over which theradiation thermometer operates.E2758 1023.1.42.1 DiscussionSpectr
34、al range is sometimes referredto as bandwidth.3.1.42.2 DiscussionThese limits are generally defined asthe wavelengths where the power or signal is attenuated by adefined amount.3.1.43 spectral response, nthe numerical quantity of agiven phenomenon at a specific wavelength in the electromag-netic spe
35、ctrum.3.1.44 standard atmosphere, na model of how electro-magnetic radiation is transmitted through the atmosphere basedon variations in pressure, temperature and humidity.3.1.45 surface-modifying material, nany material that isused to change the emissivity of the specimen surface.3.1.46 table of of
36、fsets, na list of calibration points andcalibration adjustments to be used when no internal calibrationadjustment is available.3.1.47 thermal radiation, nelectromagnetic radiationwhich is caused by an objects temperature and is predicted byPlancks Law.3.1.48 thermal shock, nsubjecting an IR thermome
37、ter to arapid temperature change.3.1.49 transmittance (t), nthe ratio of the radiant fluxtransmitted through a body to that incident upon it.3.1.50 true temperature, ntemperature attributed to aparticular site of a subject or object of measurement andaccepted as having a specified uncertainty.3.1.51
38、 wideband, adjreferring to the situation where thespectral range of an instrument is at least110 of its centerwavelength.4. Significance and Use4.1 This guide provides guidelines and basic test methodsfor the use of infrared thermometers. The purpose of this guideis to provide a basis for users of I
39、R thermometers to make moreaccurate measurements, to understand the error in measure-ments and reduce the error in measurements.5. Basic Use of IR Thermometry5.1 General Considerations5.1.1 An IR thermometer can be used in a number ofapplications. Although they are generally not as accurate ascontac
40、t thermometers, their quickness of measurement andtheir ability to measure the temperature of an opaque surfacewithout contacting it make them desirable instruments forsome temperature measurements.5.1.2 Most handheld IR thermometers are equipped with atrigger to start and stop the measurements.5.1.
41、3 As objects vary in temperature, they emit a varyingamount of thermal radiation. This amount of thermal radiationis predictable based on the objects temperature, emissivity andreflected temperature.5.1.4 Handheld IR thermometers measure thermal radiationin a given spectral range and determine the r
42、elationshipbetween the measured thermal radiation and temperature. Thesensor mainly used in these instruments is a thermopile.5.2 Basic IR Measurement5.2.1 Before making a measurement, the emissivity settingof the IR thermometer should be set to the objects effectiveemissivity in the instruments spe
43、ctral range. Some IR ther-mometers do not allow the user to adjust the emissivity becausetheir emissivity is fixed. In these cases there are mathematicalcompensations that can be made.5.2.2 To make a measurement, the IR thermometers lensshould be pointed at the object being measured. The measure-men
44、t should be initiated. If the IR thermometer has a trigger,this is done by pulling the trigger. The trigger should be held atleast as long as the IR thermometers specified response time.The measured temperature is usually frozen on the display afterthe trigger is released.5.2.3 Figure 1 shows a diag
45、ram of how much of a surface anIR thermometer measures. Subsection 11.1 discusses spot sizeand distance-to-size ratio.FIG. 1 Basic IR Thermometer MeasurementE2758 1035.2.4 Figure 2Fig. 2 shows how much surface area is neededfor temperature measurement when considering the IR ther-mometers spot size.
46、 The part of the figure labeled poorshows a situation where the object being measured is smallerthan the spot size. Such situations are undesirable. The part ofthe figure labeled OK shows a situation where the objectbeing measured is slightly larger than the spot size. Suchsituations should produce
47、acceptable temperature measure-ments. The part of the figure labeled better shows a situationwhere the object being measured is significantly larger than thespot size. This situation will produce the best temperaturemeasurements.5.3 Accuracy5.3.1 To make accurate measurements, many factors mustbe co
48、nsidered. The first is that the IR thermometer in useshould be calibrated with traceability to a national metrologicalinstitute such as the National Institute of Standards andTechnology (NIST). Calibration results can be implemented insubsequent measurements in two ways. If the IR thermometerhas an
49、internal calibration adjustment, the user can use thereading on the readout. Some IR thermometer calibrations willprovide a table of offsets. In such cases, the user must make amanual calculation to determine the true temperature.5.3.2 There are many other considerations in making accu-rate measurements with IR thermometry. These are discussedin the following sections.6. Wideband Instruments6.1 Most handheld low-temperature IR thermometers arewideband instruments. As a result, their meas
