Diffuse Reflectance Accessory (external) Note: This document is also available in PDF format for improved print quality. PDF files are stored in the
Description of the accessory Accessory design The DRA accessories are designed specifically to measure the reflectance or transmission of solids, liqu
Figure 10: The optical design of the external DRA. Integrating sphere An integrating sphere is an optical device used to collect and measure electr
Optics The optics chamber houses the transfer optics of the DRA accessory that direct the spectrophotometer reference and sample beams to their respec
Figure 13: Mirror M2. Figure 14: Mirror M3. Mirror M3 is a spherical mirror that condenses the sample beam onto the target sample. The mirror can b
Figure 15: Mirror M4. The accessory is shipped from in a protective wooden case. The accessory should be stored in the case when the DRA is not bein
data in the comma separated variable format (.CSV) and paste the file into the Scan data directory. Consult the online help for more details. Transmis
Purge gas connections Clean flexible tubing of 6 mm (1/4") inside diameter (Tygon PVC or equivalent). Size packed W x L x H, 500 mm x 840 mm x
Item Description Part number 3 x Uncalibrated PTFE reference plates Three PTFE plates for collecting baselines and performing calibrations. XXXX
1. Unpack M3 and screw it into the "R" position. Set the mirror alignment pins into the correct locator holes and secure the mount with t
7. Use the "T" handle and the corner (marked "Lift Here") to lift the DRA out of the box. See figure 18. Warning The acces
• Operation o Routine DRA installation o Removing the DRA from the instrument o Collecting baseline scans o 8°/h Reflectance Factor Measurements
will induce optical scattering and may reduce reflectance or transmission of these components at certain wavelengths. 1. Turn off the spectrophotom
Figure 20. Install the specular port plug. 7. Remove the accessory from the wooden container by lifting the accessory by the "T" handle an
9. Take care to align the metal edges of the DRA with the guide tabs on the edge of the instrument sample compartment. This will correctly align an
Figure 23. Place the front lock down pin into position. 10. Place the front lockdown pin into the hole in the DRA floor next to the "T" h
Figure 24. The sample holder fits onto the dovetail at either the reference or reflectance port. 16. Install the transmission sample holder at the t
Figure 25: DRA socket 21. Click the Windows Start button, then Programs, then Cary WinUV, and then Validate. Turn on the spectrophotometer. If the
Alignment check This procedure can be used to check the optical alignment of the accessory without disturbing any mirror adjustments. A one inch squar
Figure 27. Checking the beam at the reference port. 5. Mount or hold the translucent paper directly in front of the transmission port. Check that th
Figure 28: The optics of the DRA. 1. Click the Windows Start button, then Programs, Cary WinUV and then Align. 2. Click the Setup button. 3. Da
• Check that that DRA is correctly locked down onto the instrument sample compartment floor. • If the DRA is correctly installed, and misalignment p
Introduction The traditional use of the spectrophotometer is to measure the absorbance or transmission of a clear or translucent liquid or solid. Typi
11. Alternately adjust mirrors M4 and M5 to centre the reference beam on both the reference beam entrance and the reference ports such that the beam
Cary tab X mode: Mode Nanometers X mode: Start/Stop User-set range Y mode: Mode % R Y mode: Y min -5.00 Y mode: Y max 110.00 Scan controls: Ave time
Zero %R error check - alignment check 1. With the transmission ports uncovered, place the large reference plate over the reflectance port. 2. F
4. Click the Zero button and wait for the instrument to zero. 5. Place a mirror over the reflectance port, and close the sample compartment. Note th
Figure 29: The cuvette holder Installation and alignment To install the cuvette holder: Slide the cuvette holder over the dovetail so that it fits s
Centre-Mount Sample Holders A centre-mount sample holder offers two distinct advantages over the external sphere sample holders on the DRA. One is the
Alignment Occasionally, the requirement exists to conduct fine tune alignment of the beam inside the integrating sphere. Use white light operation and
Figure 31: The clip style variable angle sample holder. Figure 32: The jaw style centre mount. The width limitation of the jaw style sample holder
Alignment Upon first time use, the sample holder should be loaded into the centre-mount port and checked for proper angle alignment to the sample beam
bottom tip of the clip and the baffle. There is no need to use a diffuse reference standard with the clip style sample holder, the sphere wall serves
exhibits NIR performance that is superior to traditional coatings(1), whilst maintaining UV-Vis performance. Warning If the DRA is not used in the ma
Caution Exercise great care when loading the centre-mount cuvette holder into the integrating sphere, the sample holder is bulky and spilled sample so
Figure 34: The small spot kit lens holder, rail and lens. Note The small spot kit replacement for mirror M3 must be used instead of the standard ac
Figure 35: Installing the small spot kit. 2. Install the iris assembly in the position shown above. The mounting plate for the iris is magnetized t
4. Turn on the instrument on and allow it to warm up (approximately 2 hours). 5. Set the instrument to Zero order using the Align application. See I
Figure 37. The beam from the small spot kit with the iris partially open. 14. Remove the beam blocker from the reference beam path. 15. Replace th
Figure 38. The powder cell fits into the sample holder at the reflectance port. Figure 39. The powder cell in position at the reflectance port. The de
Sample Preparation Using the PCH-150 Powder Cell Holder Figure 40. An exploded view of the powder cell. 1. Disassemble the powder cell holder. DO NO
Figure 41. Calculating the packing density. 8. Calculate the packing density using the sample weight recorded in the previous steps. Reflectance Meas
• The sample reflectance depends upon sample handling factors, such as the packing density, surface uniformity, and characteristics of the sample. Fi
Figure 42: The optics of the double aperture accessory.
integrating sphere usually depends on the wavelength capabilities demanded by the reflectance application. The integrating sphere configuration offer
Figure 43. The double aperture attachment on the polarizer mount. The accessory optics should be aligned according to the Installation instructions
8. Block the reference and sample beam entrance ports to the integrating sphere and configure the sample beam for white light operation. 9. Observ
Figure 44. The polarizer attachment
Figure 45. The polarizer attachment in the DRA. The polarizer assembly uses the same base mount as the double aperture apparatus. Install the pol
7. Suspend white light operations and remove the blocking device from the reference beam. The accessory is aligned for polarizer operations. The base
7. Flick the lockdown lever on the front instrument panel to the left. 8. Install the guillotine/light seal. 9. Load a reflectance standard at the
Figure 47. Removing the light seal. Note The lockdown lever is accessible just underneath the DRA base plate. 5. Slide the lever on the instrument
An integrating sphere is sensitive to small-angle scatter from the sample beam coupling optics. Sometimes, the scattered radiation strikes the wall of
4. Click the Baseline button. 5. At the 100%T scan prompt, select OK. The standard at the reflectance port serves as the 100%R reference. 6. At the
4. Click the Start button. 5. If the standard reference option was used for the baseline scan, the reflectance spectra is generated automatically. If
Transmittance measurements Figure 4: Collection of scattered light by an integrating sphere. Io = incident light, Is = scattered light. In order to
3. Click the Setup button and check the parameters. Normally, the setup parameters for the application should match those used for the baseline scan.
1. Collect a Baseline scan, following the procedures specific to transmission measurements. If the sample resides on a substrate, load an untreated s
Variable Angle Reflectance Measurements (Centre-Mount Sample Holder) The DRA can collect variable angle of incidence reflectance data when a centre-mo
5. Remove the sample from the sample holder clip and load the empty sample holder into the centre-mount port. 6. Load Spectralon reflectance standa
Figure 49. The beam falling on the reference mounted in the jaw style centre mount. 4. Examine the path of the reference beam inside the integrating
Absorbance Measurements (Cuvette Centre-Mount Sample Holder) The following procedure can be used for obtaining absorbance measurements with a centre-m
7. Click the Setup button and check the parameters. Normally, the setup parameters for the application should match those used for the baseline scan.
Transmission Measurements (Small Spot Kit) At the transmission port location, the DRA small spot kit can be used to measure a small test sample, or to
6. Load the sample at the transmission port. Do not change the configuration of the integrating sphere in any other way. 7. Click the Setup button an
of incidence. If the beam is off centre or will not fit on the sample, either adjust the sample mounting in the sample holder or re-adjust the sample
Factors affecting accuracy or precision Below are the major factors that may affect the accuracy of measurements when using the DRA. Aperture area/to
14. If the standard reference option was used for the baseline scan, the reflectance spectra is generated automatically. If the simple or zero baseli
9. Click the Setup button and check the parameters. Normally, the setup parameters for the application should match those used for the baseline scan.
problem. Impact of these factors can be minimized if you can localize the beam to the target area of the sample using the small spot kit so the beam j
Applying a Nitrogen Purge The Cary 4000/5000/6000i instruments are fitted with connection points for purging the optical system with nitrogen to enhan
1. Instrument * 2. External DRA 3. Tubing 4. Flow meters 5. Shut-off valves 6. Manifold 7. Pressure regulator 8. Nitrogen control valve *Refer
NIR reflectance measurements (not for Cary 4000) Note Parameters activated by a radio button that are not specifically mentioned in the following pro
Data interval (nm) 1.000 Scan rate (nm/min) 600.00 SBW (nm) 2.00 NIR controls Ave time (s) 1.000 Data interval (nm) 2.000 Scan
7. Select the Baseline button from the Scan dialog. Follow the on-screen prompts to perform a 100%T baseline scan and a 0%T baseline scan. Hot Tip
Options tab SBW/Energy: Fixed SBW ON SBW/Energy: SBW (nm) 2.00 SBW/Energy: Beam mode Double SBW/Energy: Slit height Reduced Source: Lamps UV-Vis Sourc
8. Remove the specular port plug and install the light trap in its place and click the Start button to collect the diffuse-only data. 9. From t
Sample recess Theory assumes that the sample is placed coincident with the inside of the sphere wall, however the sample is placed against the outside
UV/VIS 0%T Correction This calibrates the photomultipliers for 0%T (electronic zero) effects. This is executed every time the instrument is switched o
instrument is fully warmed up would be beneficial. NIR 0%T correction This closes the shutter and calibrates the NIR detector for 0 %T errors. If a DR
Show status display ON Options tab SBW/Energy: Beam mode Double SBW/Energy: Slit height Reduced Source/Detector: Lamps UV-Vis Source: Source changeov
1. Select the Baseline button in the Scan dialog box. Follow the on-screen prompts to perform a 100%T baseline scan and a 0%T baseline scan. Hot T
1. Remove the accessory from the wood container and set it on a flat surface. 2. Check that each mirror mount in the optics chamber is fastened secu
Standards Reference surfaces for reflectance and transmission in the solar wavelengths are available from (among others) Labsphere in the USA, the Nat
Division of Electrical Science National Physical Laboratory Teddington, Middlesex TW11 OLW UK. Troubleshooting Warning This instrument contains elect
References 1. Weidner V.R., Hsia J.J: J.Opt.Soc.Am. 71/7 (1981) 2. Zwinkels J., Dodd C.X.: Workshop on Optical Property Measurement Techniques, Com
(clip) difference angles. Samples are clipped into place. Centre mount cuvette holder Centre mount holder for cuvettes. Fits into the top of the sphe
Differences between the standard and sample It is important that the reference material be of a similar reflectivity and have similar properties to th
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