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Article
Omnidirectional thermal anemometer for low airspeed and multi-point measurement applications
Computers and Electronics in Agriculture
  • Yun Gao, Iowa State University and Huazhong Agricultural University
  • Brett C. Ramirez, Iowa State University
  • Steven J. Hoff, Iowa State University
Document Type
Article
Publication Version
Accepted Manuscript
Publication Date
9-1-2016
DOI
10.1016/j.compag.2016.06.011
Abstract

Current control strategies for livestock and poultry facilities need to improve their interpretation of the Thermal Environment (TE) that the animals are experiencing in order to provide an optimum TE that is uniformly distributed throughout the facility; hence, airspeed, a critical parameter influencing evaporative and convective heat exchange must be measured. An omnidirectional, constant temperature, Thermal Anemometer (TA) with ambient dry-bulb temperature (tdb) compensation was designed and developed for measuring airspeeds between 0 and 6.0 m s−1. An Arduino measured two analog voltages to determine the thermistor temperature and subsequently the power being dissipated from a near-spherical overheated thermistor in a bridge circuit with a transistor and operational amplifier. A custom wind tunnel featuring a 0.1 m diameter pipe with an access for TA insertion was constructed to calibrate the TA at different temperatures and airspeeds, at a constant relative humidity. The heat dissipation factor was calculated for a given airspeed at different ambient temperatures ranging from 18 °C to 34 °C and used in a unique fourth-order polynomial regression that compensates for temperature using the fluid properties evaluated at the film temperature. A detailed uncertainty analysis was performed on all key measurement inputs, such as the microcontroller analog to digital converter, TA and tdb thermistor regression statistics, and the calibration standard, that were propagated through the calibration regression. Absolute combined standard uncertainty associated with temperature corrected airspeed measurements ranged from 0.11 m s−1 (at 0.47 m s−1; 30.3% relative) to 0.71 m s−1 (at 5.52 m s−1; 12.8% relative). The TA system cost less than $35 USD in components and due to the simple hardware, this thermal anemometer is well-suited for integration into multi-point data acquisition systems analyzing spatial and temporal variability inside livestock and poultry housing.

Comments

This is a manuscript of an article published as Gao, Yun, Brett C. Ramirez, and Steven J. Hoff. "Omnidirectional thermal anemometer for low airspeed and multi-point measurement applications." Computers and Electronics in Agriculture 127 (2016): 439-450. DOI: 10.1016/j.compag.2016.06.011. Posted with permission.

Creative Commons License
Creative Commons Attribution-Noncommercial-No Derivative Works 4.0
Copyright Owner
Elsevier B.V.
Language
en
File Format
application/pdf
Citation Information
Yun Gao, Brett C. Ramirez and Steven J. Hoff. "Omnidirectional thermal anemometer for low airspeed and multi-point measurement applications" Computers and Electronics in Agriculture Vol. 127 (2016) p. 439 - 450
Available at: http://works.bepress.com/brett-ramirez/25/