Wireless Sensor and Actuator Networks for Lighting Energy ...

Subject
No.
Table 8-1 Summary of the sensor placement experiment.
Average meter
reading
Average fused
reading
Deviation of fused reading from
meter reading
Mean
Standard
deviation
1 500.83 499.41 1.42 1.49
2 518.23 519.77 1.55 1.77
3 576.36 488.21 88.16 9.65
4 366.93 318.66 48.28 6.90
5 557.11 493.72 63.39 4.73
6 602.10 475.42 126.68 3.62
7 582.33 433.02 149.32 2.68
8 568.07 476.26 91.81 2.18
9 511.94 554.84 42.90 0.94
10 1026.09 1151.94 125.85 2.35
In two out of the ten cases, subjects No. 1 and 2, the fused values closely
matched the meter readings with less than 1.5% deviation. Figure 8-6 (a) plots the
readings of one such case along with a picture of the sensor locations in Figure 8-6 (b),
where the circled numbers indicate the identification number of the mote photosensors.
In both cases, one of the three sensor measurements was very close to the meter
readings, another one was constantly higher than the meter readings, and the other one
was constantly lower. Nonetheless, all the three sensor measurements were within 4.5%
of the meter readings on average. Although the sensors were not placed in exact same
pattern in both cases, they were spread out to surround the occupants’ working area but
still close to the center of the working area in general. These two were the ideal cases as
the locations of the sensors rendered the fused values to effectively represent the real
lighting conditions perceived by the participants. Also, all the sensor readings were in a
pertinent range of the real task illuminance except those that were perturbed or lost.
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