Accuracies of Lysimeter Data Acquisition Systems

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by Daniel K. Fisher, Oklahoma State Univ, Stillwater, United States,
Richard G. Allen, Oklahoma State Univ, Stillwater, United States,

Document Type: Proceeding Paper

Part of: Lysimeters for Evapotranspiration and Environmental Measurements:

Abstract: Electronic dataloggers are integral parts of most weighing lysimeter systems. Dataloggers supply excitation voltages to lysimeter load cells and measure resulting voltage signals. Resolution and accuracy of lysimeter measurements are very much dependent on resolutions and accuracies of the datalogger system. Four common datalogger models were tested with cantilever load cells used within a weighing lysimeter system. The objectives were to determine the effects of numbers of internal data bits used in analog-to-digital signal conversion, and observation sample size on data resolution and accuracy. Consistency of measurements was also tested and is expressed in terms of lysimeter mass changes and data bit band widths. It was found that the number of internal data bits used in internal analog-to-digital conversions within data-loggers most influenced lysimeter accuracy. Large numbers of observations over short time intervals improved measurement resolution to ranges which were less than one bit of band width. Small differences were found to exist among excitation channels and among input channels on dataloggers tested.

Subject Headings: Measuring instruments | Data processing | Excitation (physics) | Load factors | Data collection | Errors (statistics) | Model accuracy | Integrals |

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