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From a logical point of view we have three types of things.
- SensorsSensor
- Data processor
- Actuator
Sensor (data collector)
A sensor is any device which detects and reports physical phenomena. Not all measuring devices are sensors. In order to qualify as a sensor the device must also report its findings. Reporting could take the form of allowing interrogation of results stored in memory, the broadcasting of results, or open/closing a switch to allow current to flow or cease flowing. Examples include the following:
- a thermometer the measures temperature
- a proximity switch which determines when something is within a fixed range of the sensor
a strain gauge which measures the torque on the deck of a bridge
- a NOx detector
- an automobile speed detector
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A Data Processor transforms input data (typically from Sensors), applies policies (e.g., access management), and either reports the results or uses them directly to manage an actuator. A Data Processor may receive input from a Sensor measuring the angle of the sun in order to calculate the optimal position of a solar array. It might then send instructions to an Actuator to turn the array towards the sun.
Actuator
An Actuator is a device that causes a physical action when prompted by a Data Processor, or directly by a human. Actions could include opening/closing a circuit, starting/stopping a motor, sounding an alarm, or detonating an explosion. Actuators can do more than merely start or stop an action. They could also cause a vehicle to change speed. Typically, however, Actuators are digital on/off devices offdevices and variable control is provided by incorporating a Data Processor to manage the amount of time the Actuator is on or off.
The IoT from physical point of view
The logical view on its own does not help much in order to explain identity issues in the IoT. That why we have to extend our view to the physical objects and the underlying infrastructure. Important aditional elements of an IoT infrastructure
Object Identifiers (Scott)
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