Carlos Manuel Rodrigues Machado Autonomic Ubiquitous Computing

4.3.7 Temperature and Humidity
Temperature can be sensed using very simple thermal resistors or more sophisticated
temperature sensors with built-in driving circuits. Such temperature sensors are available with
analogue or digital interfaces and offer high accuracy.
Sensors for humidity are more complex and also more expensive than sensors for
temperature. Humidity sensors are available based on capacitive and resistive technologies and
also as modules that provide an analogue or digital output that is proportional to the humidity level.
Humidity sensors react in a matter of seconds to changes.
These environment measurements can help to determine if a space is being used by any
human as the humidity and temperature tend to increase in that situation.
4.3.8 Weight
The weight measure is obtained using load cells. These convert a force into an electrical
signal. These types of sensors are widely deployed in industrial systems. Load cells can measure
from milligrams to the weight of several hundred tons. The resolution is dependent on the range
and also on the quality of the device. Load cells are available based on different technologies and
also using different interfaces. Commonly used industrial load cells, based on resistive technologies,
incorporate a Wheatstone-Bridge and provide an analog output signal. Off-the-shelf load cells are
available in different physical shapes and sizes.
The weight in combination with other measurements can be used to associate actions to any
particular user, contributing to the enrichment of the context.
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