Calibration lamps

Fig. 14.3 (a) SBSL spectra containing Ar emission lines from 85% H2S04 and the best fit synthetic spectra at 15,000 K. (b) SBSL spectra and the low pressure spectra from a Hg(Ar) calibration lamp [11] (reprinted with permission from Annual Reviews)... 

The UV visible measurements are performed using a commercial HR 2000 high-resolution fibre optic Ocean Optics spectrophotometer equipped with a halogen light source HL2000. The detector is a linear silicon CCD array. The spectral resolution measured with a Hg-Ar calibration lamp is better than 0.2 nm. 

Medium-resolution absorption spectrometer emission spectrometer with red-sensitive photomultiplier or CCD detector laser excitation source such as listed in Table 1 (or medium pressure mercury arc such as described in earlier editions of this text) neon calibration lamp and power supply (available from, e.g.. Oriel Corp., Stratford, CT) reagent-grade iodine 100-mm glass cell with Teflon stoppers for absorption studies heating tape with controlling Variac 50-mm cell for emission studies vacuum system, preferably with a diffusion pump and cold trap, for pumping down emission cell. 

Figure 3.6-8 Experimental set-up for CARS spectroscopy in the condensed phase. A = aperture AL = achromatic lens BS = beam. splitter CL = calibration lamp D = diffuser Dl, D2 = diodes FR = double Fresnel rhombus L = lens M = mirror P = Glan-Thompson polarizer PA = preamplifier PHS = Prism Harmonic Separator PM = photomultiplier PR = linear dispersing prism arrangement S = shutter (Materny et al., 1992a).

The lux meter is used in photometry and is simply a radiometer with a spectral responsiveness that closely matches the visual response of the human eye, thus measuring incident radiant power in the visible region of the electromagnetic spectrum. In this case, the unit of measurement is the illuminance in lux and is calibrated against a specific tungsten lamp. The lux meter should be provided with a set of correction factors to enable compensation for differences in spectral response for lamps with emission spectra different from the calibration lamp. 

For a detector with a finite area, this expression can be used provided the detector subtends a sufficiently small solid angle (see Fig. 4.5). The condition recommended by CIE [19] is that Q < 0.01 sr. Under these conditions, the luminous intensity (A, in candelas) can be obtained by comparing the signal from the PLED to that obtained from a calibrated lamp. The brightness is then given by L = A/n r2. 

Obviously, temperature is an important parameter and pyrometers must be calibrated on a regular basis. Figure 11.24 shows a typical layout for the calibration of a pyrometer. The calibration lamp (GEC) [30], must be calibrated to a National standard e.g. NAMAS, and should be mounted upright in front of the pyrometer, which should be positioned at a distance, d, to enable it to be focused on the lamp filament. It is convenient to mount the pyrometer on a laboratory jack to adjust the height relative to the lamp filament. 

It is also essential that emission spectra are corrected for the instrumental function estabUshed with a standard calibrated lamp. It is wise not to use the calibration curve given by the manufacturer of the spectrometer and to re-measure this instrumental function at regular intervals because many items influence it, particularly the emission intensity of the excitation lamp and the quantum efficiency of the detector (which both decrease with time). In case (27a) is used, the excitation instmmental function has to be known as well. Regarding the standard, it is best when its emission spectrum overlaps the emission spectmm of the unknown... 

Calibration Lamps with Emission Line Locations in Nanometers)... 

Calibration lamps are used to check the wavelength accuracy for ultraviolet and visible spectrophotometers. The main lamps used include... 

If you do not have a calibrated lamp, one simple and fairly reliable method is to obtain the necessary correction factor by comparing the emission spectrum of a standard substance obtained with your own instmment with that of the spectmm of the same substance, but corrected, as shown in the literature. The main standards and their corrected spectra, which cover the region between 300 and 800 nm, are listed in [1]. 

Atypical optical pjrometer consists of a power supply and an optical system. The optical system incorporates a telescope, a calibrated lamp, a filter for viewing nearly monochromatic radiation, and an absorption glass filter (see Fig. M-8). The filament of the lamp and the test body are viewed simultaneously. The filament current is adjusted imtil the filament image disappears in the image of the test body. 

The static array irradiance calibration system uses a radiometer and can be preformed by the machine operator. A rotating drum tester is calibrated with a multi-step procedure using a special calibration lamp. Generally, calibration of a rotating drum tester is done by an outside service technician. 

---