GC/Computer Interfacing Using LabVIEW

1. GC/Computer Interfacing Using LabVIEW Courtney Arnott April 22, 2002 CHEM 250

2. Dedication • Bryan Alphin Bente (SBC Class of 1969) • Rachel Snider

3. LabVIEW • Graphical programming language (G) • Data acquisition • Instrument control • VI • Front panel • Block diagram 1. “LabVIEW User Manual,” p.1-1 and 1-2. National Instruments, 1992.

4. Goals • Interface GC with computer • Create data acquisition program • Display, report, integrate peaks

5. A-to-D Converter • Converts voltage signal to logic state • Two types • Staircase • Successive-approximation 2. Skoog, Holler, and Nieman. Principles of Instrumental Analysis, Fifth Edition. Saunders College Publishing: Philadelphia, 1998.

6. Integrating GC and Computer • Sends voltage signal from GC to A-D converter • Max signal = 1V

7. Testing the Connection • Used wires and voltmeter • Ran with computer interface and plotter simultaneously • Adjusted connection to achieve + voltage

8. Front Panel

9. Block Diagram

10. Sub-VIs • Separate VI used for one particular function • Make main program more organized • Can be used in other programs • Three Sub-VIs • Peak • Limit • Table

11. Sub-VI: Peak • Y-values, Peak Min (set by user) • Finds peak amplitudes and locations

12. Sub-VI: Limit • Filters out solvent front • All y values over 0.65 are discarded from array • Corresponding x values removed

13. Sub-VI: Table • Integrates peaks • Formats locations, amplitudes, and areas into table

14. Program Results • Collects data and finds peak • Programmed to ignore solvent front • Displays peaks in table format • User information inputs

15. Future Program Goals • Fix integrate procedure • Export data to file • Publish reports