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  • Topic: Ultraviolet, LabVIEW, Spectrophotometry
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  • Published : December 15, 2012
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Spectrophotometry
Danial J. Neebel, Joseph R. Blandino, and David J. Lawrence, College of Integrated Science and Technology James Madison University

Instructor’s Portion
Summary
In this experiment, data collection is simplified to allow students to focus on the measured phenomena. They will measure the transmittance as a function of wavelength for three different materials, and calculate the absorption coefficient as a function of wavelength for two of them. LabVIEW facilitates the data taking process by recording the measurements and doing some simple mathematics. In essence, the use of LabVIEW converts older analog spectrophotometers into digital spectrophotometers with manual dials and setup. This is the best of both worlds; students get hands-on experience with the equipment without being burdened by hand recording of data. The lab uses a VI written to work with a spectrophotometer that has an analog voltage output corresponding to the transmittance (signal range is from 0 to 1V).

Uses
The spectrophotometry lab has applications in electrical engineering, mechanical engineering, chemistry, and physics. Chemists may want to measure the transmittance through chemical samples to determine the sample elements.

Equipment List
• Computer running Windows, Macintosh, Linux, Sun, or HP-UX (visit http://www.ni.com/labview/lv_sysreq.htm for requirements specific to your operating system). Breadboard Connector Starter Kit from National Instruments (part number 777448-40)



− LabVIEW Full Development System − PCI-6024E Data Acquisistion Board − SC-2075 Breadboard Connector − SH68-68-EP Shielded Cable • • • • • • Spectrophotometer (i.e. Hitachi 100-10 UV/VIS) Silica, glass, plastic, color filter, and sunglass (green, gray-brown, metallic, and polarized) samples. A micrometer or calipers used to measure the thickness of the materials. Adhesive tape for securing samples to the sample holder of the spectrophotometer. A piece of black construction paper used for calibrating the spectrophotometer. Websites − Hitachi — www.hitachi.com − National Insturments — www.ni.com

Setup
Follow the steps listed to prepare the workstations for this experiment. The instructions assume you are using the equipment list shown previously. Note: Most of the manuals that are referred to ship with National Instruments hardware and software. If you can’t find your hardcopy of the manuals, you can get them online at http://www.ni.com/manuals. If you encounter problems during setup, contact technical support at http://www.ni.com/support. Before the Day of the Lab 1. Install LabVIEW (see the LabVIEW Release Notes for your version of LabVIEW). 2. Install your PCI-6024E board (see the 6023E/6024E/6025E User Manual). 3. Configure the SC-2075 Breadboard Connector (see the SC-2075 User Guide).

Spectrophotometry

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4. Cable the PCI-6024E to the SC-2075 Breadboard Connector with the SH68-68-EP. 5. Configure the PCI-6024E board (See the NI-DAQ Release Notes for your version of NI-DAQ). 6. Create the following directory in your LabVIEW folder: \\LabVIEW\Experiments\Spectrophotometry.

7. Copy Spectrophotometry.llb into the Spectrophotometry folder you just created. 8. Connect the analog output of the spectrophotometer to analog input channel 0 (CH0) on the SC-2075 Breadboard Connector. 9. Any other setup is specific to your own spectrophotometer. 10. Conduct a run-through of the lab procedure the students will perform. On the Day of the Lab 1. One of the materials the students test in this lab is silica (SiO 2 ). Measure and record the thickness of the silica sample. 2. Because of the brittle nature of this material, install the silica sample into Position 2 on the spectrophotometer before the students arrive for lab. 3. Prepare other sample materials at the workstations. 4. Turn on the computers.

References
• • John A. Allocca, Transducers: Theory and Applications, Reston Pub. Co. Wheeler, Anthony J. and Ganji, Ahmad R. (1996),...
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