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Statistical Evaluation of Instruments Designed to Measure Volumetric Water Content of Soilless Container Media
- If decisions are to be made concerning when and how much to irrigate container-grown plants, then procedures for measuring the accuracy and reliability of Volumetric Water Content (VWC) sensors should be developed. Three statistical properties were used to characterize the quality of VWC sensor data for this study: (1) bias, (2) variance, and (3) measurement system discrimination. The objectives of the tests reported here were to evaluate the measurement capability of three commercially available moisture sensors. Based on standardized repeatability and reproducibility measurement procedures for determining variance, estimated standard deviation (measurement error) for the WET Sensor was 2.11% VWC while the HydroSense and the ThetaProbe were 1.21 and 1.43%, respectively. Bias readings for all three instruments were 3% to 5% below a 30% reference value. Evaluation of discrimination in terms of measurement system acceptance calculations found all three sensors were well within a 10% to 30% guideline that compares measurement error to the range of expected values to be discriminated.
Hansen, R.C. , Christman, J.C. , Derksen, R.C.
soilless media , water content , sensors , electrical conductivity , statistical analysis , fertigation , nutrient solutions , microirrigation
- Includes references
- Applied engineering in agriculture 2006 Sept., v. 22, no. 5
Journal Articles, USDA Authors, Peer-Reviewed
- Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.