Feasibility Study of Sensors on Tmote Sky for Wireless Sensor Network Applications
Date Issued
2007
Date
2007
Author(s)
Hsieh, Tsung-Hsun
DOI
zh-TW
Abstract
Wireless sensor network (WSN) becomes popular due to the rapid development of IT, MEMS and IC technology. Features such as low electricity consumption, low cost, small size, self-adjustable and capable of wireless communication make it a good tool to develop ambient intelligent system. The objective of this research is to investigate on PAR and TSR light sensors (S1087, S1087-01, Hamamatsu, Japan) and temperature (T) /relative humidity (RH) sensors (SHT 11, Sensirion AG, Switzerland) on Tmote Sky, which is a commercially available ZigBee based (following IEEE 802.15.4 protocol) WSN related product of Moteiv company of US.
Portable spectroradiometer (LI-1800, LICOR, USA), standard thermometer (Tomei, Japan) and saturated solutions of 9 types of salt were used as standards to validate the data measured by PAR, TSR, T and RH sensors of Tmote Sky. Latter 2 were also validated with HOBO T/RH data logger, which is popular in environmental measurement.
Results of light measurements shows Tmote Sky is quite accurate when measuring indoor light or LED panels used. However, for outdoor solar radiation measurement, the sensors fail to provide accurate readings. Some improvements such as a transparent film with the given transmittance need to be used to constraint sensor output current below 4 μA.
Results of Temperature measurement show 3 to 4 degree C difference. Under 25 degree C and 11.30~93.58 % RH range provided by saturated solution of 9 types of salt, the error of RH sensor on Tmote Sky range from 8 to -26 %. The arrangement of PAR, TSR light sensors and T/RH sensors closely connected is a poor design. Light measurement requires direct impact of light beam and this will affect accuracy of T/RH sensors. In a sunny day, the error can be as large as 16.3 degree C and 17.4% RH. When measuring T and RH, prevent direct radiation is needed thus light sensors with certain light guide is needed to provide accurate readings.
Subjects
無線感測網路
溫度
濕度
光合作用有效光
總輻射能
ZigBee
Tmote Sky
Wireless Sensor Network
Temperature
Relative humidity
PAR
TSR, ZigBee
Type
thesis
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