| dc.creator | Brown, Denise Lynn | |
| dc.date.accessioned | 2012-06-07T23:12:10Z | |
| dc.date.available | 2012-06-07T23:12:10Z | |
| dc.date.created | 2002 | |
| dc.date.issued | 2002 | |
| dc.identifier.uri | https://hdl.handle.net/1969.1/ETD-TAMU-2002-THESIS-B77 | |
| dc.description | Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item. | en |
| dc.description | Includes bibliographical references (leaves 90-91). | en |
| dc.description | Issued also on microfiche from Lange Micrographics. | en |
| dc.description.abstract | This research focuses on the design and development of a control system for hypobaric plant growth chambers. The chambers will be used to determine the effects of reduced pressure on plant processes and growth. There are two low pressure plant growth systems discussed. The first system consists of two growth chambers that are controlled by a single computer. The control algorithms for measuring and controlling pressure and measuring temperature inside the chambers are written in LabVIEW. This system has no gas concentration measurement or control. The second system has six growth chambers. The pressure and gas concentrations within each chamber are controlled by PIC16F877 microcontrollers. The microcontrollers also monitor and record temperature. The setpoints for pressure, oxygen concentration, and carbon dioxide concentration are entered into a LabVIEW program on the main computer, and the data is sent to the microcontrollers via serial communication by this same program. Once the microcontrollers have finished adjusting the pressure gas concentrations based on the setpoints and the current conditions, each microcontroller returns values for pressure, temperature, and the amount of each of the three component gases (nitrogen, oxygen, and carbon dioxide) added. These values are read by the LabVIEW program on the computer and stored in files for analysis. The concentrations of the component gases are measured by a process gas chromatograph. The two-chamber system has limited usage because of a lack of gas control. Tests of the larger system showed that the system can maintain setpoint pressures in the chambers for long durations. The microcontrollers properly adjust gas concentrations using the gas addition algorithm based on setpoints and current concentrations in the chamber. The system will be used to determine the effects of various pressures and gas concentrations on plant processes and development. | en |
| dc.format.medium | electronic | en |
| dc.format.mimetype | application/pdf | |
| dc.language.iso | en_US | |
| dc.publisher | Texas A&M University | |
| dc.rights | This thesis was part of a retrospective digitization project authorized by the Texas A&M University Libraries in 2008. Copyright remains vested with the author(s). It is the user's responsibility to secure permission from the copyright holder(s) for re-use of the work beyond the provision of Fair Use. | en |
| dc.subject | biological and agricultural engineering. | en |
| dc.subject | Major biological and agricultural engineering. | en |
| dc.title | A distributed control system for low-pressure plant growth chambers | en |
| dc.type | Thesis | en |
| thesis.degree.discipline | biological and agricultural engineering | en |
| thesis.degree.name | M.S. | en |
| thesis.degree.level | Masters | en |
| dc.type.genre | thesis | en |
| dc.type.material | text | en |
| dc.format.digitalOrigin | reformatted digital | en |
