1、Designation: G138 06G138 12Standard Test Method forCalibration of a Spectroradiometer Using a Standard Sourceof Irradiance1This standard is issued under the fixed designation G138; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONA standardized means of performing and reporting calibration of the spectroradiometer for spectralirradiance
3、 measurements is desirable.This test method presents specific technical requirements for a laboratory performing calibration ofa spectroradiometer for spectral irradiance measurements. A detailed procedure for performing thecalibration and reporting the results is outlined.This test method for calib
4、ration is applicable to spectroradiometric systems consisting of at least amonochromator, input optics, and an optical radiation detector, and applies to spectroradiometriccalibrations performed with a standard of spectral irradiance with known irradiance values traceableto a national metrological l
5、aboratory that has participated in intercomparisons of standards of spectralirradiance. The standard must also have known uncertainties and measurement geometry associatedwith its irradiance values.1. Scope1.1 This test method covers the calibration of spectroradiometers for the measurement of spect
6、ral irradiance using a standardof spectral irradiance that is traceable to a national metrological laboratory that has participated in intercomparisons of standardsof spectral irradiance.1.2 This method is not limited by the input optics of the spectroradiometric system. However, choice of input opt
7、ics affects theoverall uncertainty of the calibration.1.3 This method is not limited by the type of monochromator or optical detector used in the spectroradiometer system. Partsof the method may not apply to determine which parts apply to the specific spectroradiometer being used. It is important th
8、at thechoice of monochromator and detector be appropriate for the wavelength range of interest for the calibration. Though the methodgenerally applies to photodiode array detector based systems, the user should note that these types of spectroradiometers oftensuffer from stray light problems and hav
9、e limited dynamic range. Diode array spectroradiometers are not recommended for usein the ultraviolet range unless these specific problems are addressed.1.4 The calibration described in this method employs the use of a standard of spectral irradiance. The standard of spectralirradiance must have kno
10、wn spectral irradiance values at given wavelengths for a specific input current and clearly definedmeasurement geometry. Uncertainties must also be known for the spectral irradiance values. The values assigned to this standardmust be traceable to a national metrological laboratory that has participa
11、ted in intercomparisons of standards of spectral irradiance.These standards may be obtained from a number of national standards laboratories and commercial laboratories. The spectralirradiance standards consist mainly of tungsten halogen lamps with coiled filaments enclosed in a quartz envelope, tho
12、ugh othertypes of lamps are used. Standards can be obtained with calibration values covering all or part of the wavelength range from 200to 4500 nm.1 This test method is under the jurisdiction ofASTM Committee G03 on Weathering and Durabilityand is the direct responsibility of Subcommittee G03.09 on
13、 Radiometry.Current edition approved June 1, 2006June 1, 2012. Published July 2006. Originally approved in 1996. Last previous edition approved in 2003 as G138 03. DOI:10.1520/G0138-06.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of
14、 what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered
15、 the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States11.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to
16、establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.22. Referenced Documents2.1 ASTM Standards:3E772 Terminology of Solar Energy ConversionE1341 Practice for Obtaining Spectroradiometric Data from Radiant Sources for Colorimetry2.2
17、Other Documents:CIE Publication No. 63 4The Spectrodiometric Measurement of Light SourcesNIST Technical Note 1927: Guidelines for Evaluation and Expressing Uncertainty of NIST Measurement Results53. Terminology3.1 General terms pertaining to optical radiation and optical measurement systems are defi
18、ned in Terminology . Some of themore important terms from that standard used in this paper are listed here.3.1.1 bandwidth, nthe extent of a band of radiation reported as the difference between the two wavelengths at which theamount of radiation is half of its maximum over the given band.3.1.2 diffu
19、ser, na device used to scatter or disperse light usually through the process of diffuse transmission or reflection.3.1.3 integrating sphere, na hollow sphere coated internally with a white diffuse reflecting material and provided withseparate openings for incident and exiting radiation.3.1.4 irradia
20、nce, nradiant flux incident per unit area of a surface.3.1.5 monochromator, nwith respect to optical radiation, the restriction of the magnetic or electric field vector to a singleplane.an instrument for isolating narrow portions of the optical spectrum of a light source3.1.6 polarization, nwith res
21、pect to optical radiation, the restriction of the magnetic or electric field vector to a single plane.3.1.7 radiant flux, nthe time rate of flow of radiant energy measured in watts.3.1.8 spectral irradiance, nirradiance per unit wavelength interval at a given wavelength.3.1.9 spectroradiometer, nan
22、instrument for measuring the radiant energy of a light source at each wavelength throughout thespectrum.3.1.10 ultraviolet, adjoptical radiation at wavelengths below 400 nanometres.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibration subsystems, nthe instruments used to supply and mo
23、nitor current to a standard lamp during calibration,consisting of a DC power supply, a current shunt, and a digital voltmeter.3.2.2 National Metrological Institution (NMI), nA nations internationally recognized standardization laboratory.3.2.2.1 DiscussionThe International Bureau of Weights and Meas
24、urements (abbreviation BIPM from the French terms) establishes the recognitionthrough Mutual RecognitionAgreements. See http:/www.bipm.org/en/cipm-mra. The NMI for the United States ofAmerica is theNational Institute for Standards and Technology (NIST).3.2.3 passband, nthe effective bandwidth (c.f.)
25、, or spectral interval, over which the spectroradiometer system transmits at agiven wavelength setting. Expressed as full-width at one-half maximum, as in bandwidth. A function of the linear dispersion(nm/mm) and slit or aperture widths (mm) of the monochromator system.3.2.4 primary standard of spec
26、tral irradiance, na broad spectrum light source with known spectral irradiance values atvarious wavelengths which are traceable to a national metrological laboratory that has participated in intercomparisons of standardsof spectral irradiance.3.2.5 responsivity, nsymbol R = dS/d, S is signal from sp
27、ectroradiometer detector, is radiant flux at the detector.3.2.6 secondary standard of spectral irradiance, na standard calibrated by reference to another standard such as a primary orreference standard.2 Available from Secretary, U.S. National Committee, CIE, National Institute of Standards and Tech
28、nology, Gaithersburg, MD 20899.the CIE, (International Commissionon Illumination), http:/ CIE Central Bureau, Kegelgasse 27, A-1030 Vienna, Austria.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standar
29、dsvolume information, refer to the standards Document Summary page on the ASTM website.4 G035 Available from American National Standards Institute, 11 West 42nd Street, 13th Floor, New York, NY 10036G138 1223.2.7 slit scattering function, nsymbol Z(o,), the responsivity of the combined detector and
30、monochromator system as afunction of wavelengths, , in the neighborhood of a given wavelength setting, o. The slit scattering function is the spectralresponsivity in the neighborhood of specific wavelength setting, o.3.2.8 spectral scattering (stray light), n light with wavelengths outside the passb
31、and of a spectroradiometer a particularwavelength setting that is received by the detector and contributes to the output signal.4. Significance and Use4.1 This method is intended for use by laboratories performing calibration of a spectroradiometer for spectral irradiancemeasurements using a spectra
32、l irradiance standard ofwith known spectral irradiance values and associated uncertainties traceableto a national metrological laboratory that has participated in intercomparisons of standards of spectral irradiance, knownuncertainties and known measurement geometry.4.2 This method is generalized to
33、 allow for the use of different types of input optics provided that those input optics are suitablefor the wavelength range and measurement geometry of the calibration.4.3 This method is generalized to allow for the use of different types of monochromators provided that they can be configuredfor a b
34、andwidth, wavelength range, and throughput levels suitable for the calibration being performed.4.4 This method is generalized to allow for the use of different types of optical radiation detectors provided that the spectralresponse of the detector over the wavelength range of the calibration is appr
35、opriate to the signal levels produced by themonochromator.5. Apparatus5.1 Laboratory:5.1.1 The room in which the calibrations are performed and especially the area surrounding the optical bench should be devoidof reflective surfaces. The calibration values assigned to the spectral irradiance standar
36、d are for direct irradiance from the lampand any radiation entering the monochromator from some other source including ambient reflections will be a source of error.5.1.2 The temperature and humidity in the laboratory shall be maintained so as to agree with the conditions under which thecalibrations
37、 of the spectral irradiance standard and the calibration subsystems were performed (typically 20C, 25C, 50 % relativehumidity).5.1.3 Air drafts in the laboratory should be minimized since they could affect the output of electrical discharge lamps.5.2 Spectroradiometer5.2.1 Monochromator:5.2.1.1 This
38、 can be a fixed or scanning, single or multiple, monochromator employing holographic or ruled gratings or prismsor a combination of these dispersive elements. For improved performance in the ultraviolet (uv)(UV) portion of the spectrum, itis recommended that a scanning double monochromator be used t
39、o achieve lower stray light levels (see Fig. 1). If themonochromator has interchangeable slits, it is important that the manufacturer document the effective bandwidth of themonochromator with all possible combinations of the slits or that these bandwidths be determined experimentally. Configurationo
40、f the slits should be such that the bandpass function of the monochromator is symmetric, preferably triangular. The bandwidthshould be constant across the wavelength region of interest and maintained between 85 % and 100 % of the measurementwavelength interval. The precision of the wavelength positi
41、oning of the monochromator should be 0.1 nm with an absoluteaccuracy of better than 0.5 nm (see Practice E1341). For improved performance in the uv, it is recommended that high orderrejection filters be inserted in the optical path in the monochromator. The purpose of the high order rejection filter
42、s is to blockradiation in the monochromator of unwanted wavelengths that could otherwise overpower the signals being measured. The effectsof variations in temperature and humidity on the performance of the monochromator should be addressed in writing by themanufacturer.5.2.1.2 Avoid mechanical shock
43、 and excessive vibration to the monochromator.The monochromator shall not be subject toshock or mechanical vibration during the calibration. This can be facilitated by the use of a vibration isolated lab table. If anyoptical parts in the monochromator are configurable by the user, refer to the manuf
44、acturer precautions about opening themonochromator and handling any parts therein.5.2.2 Optical Radiation Detector:5.2.2.1 The optical radiation detector employed by the spectroradiometer shouldshall be selected for optimal response over thewavelength range of interest. It is also important that the
45、 detector is sensitive enough to measure the levels of light that will beproduced by the monochromator when it is configured for the calibration process. The active area of the detector shouldshall beevenly illuminated by the radiation leaving the exit slit of the monochromator. A photomultiplier is
46、 typically used because of itshigh responsivity and good signal-to-noise ratio. For this reason it is recommended for use when measuring spectral irradiance inthe uv portion of the spectrum.5.2.2.2 TheAny effects of variation in temperature and humidity on the response of the detector should be docu
47、mented by themanufacturer. manufacturer shall be reported. Of all components of the spectroradiometer, the detector is usually the most sensitiveG138 123to changes in temperature. Some detectors may require cooling in order to maintain a specific temperature.Avoid mechanical shockto the detector. If
48、 the detector requires an amplifier, any reported limitations and uncertainties in the detector system must factorin the contribution of the amplifier.5.2.3 If a diode array based spectroradiometer system is used, note the following recommendations.precautions:5.2.3.1 The diode array spectroradiomet
49、er should employ internal focusing optics inwithin the monochromator.5.2.3.2 When measuring in the ultraviolet, the method of stray light should be controlledcontrol, such as by the use of high orderrejection filters or internal baffling, or both.both, shall be documented.5.2.3.3 The It is highly recommended that diode array spectroradiometerspectroradiometers should not be used formeasurements below 300 nm.nm without extensive characterization of stray light characteristics and detector performance.5.2.4 Input Optic
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