ISHS Acta Horticulturae 710: International Symposium on Greenhouses, Environmental Controls and In-house Mechanization for Crop Production in the Tropics and Sub-Tropics
THERMOMETRY IN MEDIUM-SCALE GREENHOUSE USING A SMALL NUMBER OF ACOUSTIC SENSORS |
| Authors: | K. Kudo, K. Mizutani, R. Futamata, K. Itoga, S. Sase |
| Keywords: | temperature measurement, temperature distribution, sound probe, time of flight, TOF |
| Abstract:
The paper describes a thermometry for temperature distribution in a medium-scaled greenhouse using a small number of acoustic sensors. A sound probe, which consisted of a loud speaker (SP), a microphone (MIC) and a propagation path, was the acoustic sensor that could measure a mean temperature in a comparatively large space. Sound probes measured the temperatures without occupation of working spaces in the greenhouse. Spatial mean temperature was an integral of temperature fluctuation along the sound propagation path, thus the thermometry with the sound probes was resistible for a temporal disturbance in a local point. The temperature distribution in the greenhouse was reconstructed by the sound probes. The number of propagation paths was increased by utilizing a radial transmission of the SP and specular reflections of sounds by use of acoustic reflectors. The number of acoustic sensors was reduced accordingly. The sound reflections were caused by plastic boards whose surfaces were plane. In the field experiment, the temperature distribution was measured with four acoustic sensors and eight plane boards in a horizontal space whose size was 5.0 m by 10.0 m. The temperature distribution consisted of five unit cells. The 15 thermocouples readings in the measurement space showed a good agreement with temperature distribution measured with the sound probes. | |
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