### device:

Sensor
* Many sensors act as a switch, controlling the flow of electric charges through the circuit
  - rely on mechanical structures
* Most sensors measure forces
  - intensity
  - visibility
* Some sensors also record transmitted light in the form of heat or radiation
  - are powered by batteries
  - come in shapes
  - measure height
  - produce an output voltage, current, a resistance or capacitance.
  * There are a lot of different types of sensors. Sensors are used in everyday objects
* are detectors
  - devices
  - non-invasive while actuators modify the environment
  - normally thin wires with diameters down to a few micrometers
  - often only partially selective in their responses to different gases
  - piezoelectric probes without built-in electronics
  - places on the skin over a muscle
  - responsible for adjusting outside and inside temperature
  - the fundamental components of a measurement or control system
  - triggers that fire off a message in response to some activity
* are used for collect information
* automatically dim fixtures near windows to ensure maximum use of sunlight.
* can turn off lights when people leave a room.
* connect actions to a representation of the world.
* continuously gather information from the environment.
* detect X-rays passing through the body
  - depth
  - phenomena
* directly measure soil moisture in order to maintain an ideal crop growth environment.
* enable a robot to make decisions based on an external stimulus
  - the fish to detect the presence of humans and react to their movements
* ensure the light comes on at dusk, day after day, night after night.
* exist that recognize changes in facial expression, heart rate, blood pressure, and more.
* give information
  - valuable information
* have a higher reflection in air due to surface effects of the lenses
  - power requirements
  - ranges
  - transmission ranges
* help biologists.
* includes sections.
* measure acceleration forces
  - aspects of a particular part or the world relative to that part
  - the amount of reflectance in a prescribed part of the electromagnetic spectrum
* provide accurate measurements
  - temperature measurements
* provide good optical performance
  - mechanisms for the user to interact with objects in the world
  - options
* react to changing physical conditions by altering their electrical properties.
* save energy by keeping lights off unless they are needed.
* use for experiments.
* work based on their ability to pick up compounds with a phosphorus-fluorine chemical bond.

### device | sensor:

Acoustic sensor
* Some acoustic sensors can also differentiate larval feeding within trees.
* use non-recording microphones that pick up sounds within a room.

Capacitive sensor
* are robust against effects such as condensation and temporary high temperatures.
* detect plastic materials through non metal containers, sight windows etc.

### device | sensor:

Chemical sensor
* provide equivalents of taste and smell.
* serve as an interface between biological and electronic systems.
+ Spider, Anatomy, Spider eyes and other senses
  * Spiders and other arthropods have modified their cuticles into elaborate arrays of sensors. Various sensors, mostly bristles, respond to touch, from strong contact to very weak air currents. Chemical sensors provide equivalents of taste and smell. Spiders also have in the joints of their limbs sensors that detect forces and vibrations. In web-building spiders all these mechanical and chemical sensors are more important than the eyes, while the eyes are most important to spiders that hunt actively. Like most arthropods, spiders lack balance sensors, and rely on their eyes to tell them which way is up.

Computerized sensor
* drive motorized shades, balancing daylight with energy savings.
* monitor water quality and temperature.