[is a] peripheralinput device which senses some variable in the system environment, such as temperature, and converts it to an electrical signal which can be further converted to a digital signal for processing by the computer.[2]
[is] equipment which detects, and may indicate, and/or record objects and activities by means of energy or particles emitted, reflected, or modified by objects. Note. The energy may be nuclear, electromagnetic, including the visible and invisible portions of the spectrum, chemical, biological, thermal or mechanical, including sound, blast and earth vibration.[4]
”
“
[is a] device that produces a voltage or current output that is representative of some physical property being measured (e.g., speed, temperature, flow).[5]
an electronic utility (eUtility) that measures physical properties such as temperature, acceleration, weight, sound, location, presence, identity, etc. All sensors employ mechanical, electrical, chemical, optical, or other effects at an interface to a controlled process or open environment.[7]
”
“
[a] portion of an IoT device capable of providing an observation of an aspect of the physical world in the form of measurementdata.[8]
”
Overview[]
Sensors are a type of electronic device that must produce the miniscule amount of power required to convey information at a usable error rate. Sound, light, atmospheric conditions, vibrations, and other environmental signals are all fair game for sensor designers.
Basic properties, assumptions, recommendations, and general statements about sensors include:
1. Sensors are physical; some may have an Internet access capability.
2. Sensor output is data; . . . Analog sensors such as microphones and voltmeters are counterexamples.
4. Sensors may have an identity or have the identity of the "thing" to which they are attached.
5. Sensors may have little or no software functionality and computing power; more advanced sensors may have software functionality and computing power.
9. Sensors may have an owner(s) who will have control of the data their sensors collect, who is allowed to access it, and when.
10. Sensors will have pedigree — geographic locations of origin and manufacturers. Pedigree may be unknown, and suspect.
11. Sensors may be cheap, disposable, and susceptible to wear-out over time.
12. There may be differentials in sensor security, safety, and reliability, e.g., between consumer grade, military grade, industrial grade, etc.
13. Sensors may return no data, totally flawed data, partially flawed data, or correct and acceptable data. Sensors may fail completely or intermittently. They may lose sensitivity or calibration.
14. Sensors are expected to return data in certain ranges, e.g., [1 ... 100]. When ranges are violated, rules may be needed on whether to turn control over to a human or machine when ignoring out-of-bounds data is inappropriate.
15. Sensors may be disposable or serviceable in terms of calibration, sensitivity or other forms of refresh. Complex and expensive sensors may be repaired instead of replaced.
23. The frequency with which sensors release data impacts the data's currency and relevance. Sensors may return valid but stale data. Sensor data may be "at rest" for long periods of time.
25. Sensors may transmit data about the "health" of a system, such as is done in prognostics and health management (PHM).
26. * * * When classified as an eUtility, humans can still act in a sensor-like role by manually feeding data into a NoT's workflow and data flow.
27. Humans can influence sensor performance through failure to follow policy, sensor misplacement, etc. (or their positive analogs). Humans are potential contributors to sensor failures.