Occupancy Sensor

The sensor is capable of identifying when a particular space within a building is occupied, and adjusts the lighting, heating and cooling, and other appliances accordingly.

When no one is currently occupying a given area of the building, the sensors note this and will turn off unnecessary lights as well as adjust temperature controls slightly. This helps to minimize the use of electricity during those periods when the space is not in active use.

As someone enters the space, the occupancy motion sensor recognizes the movement and automatically brings up the lights and adjusts the climate control equipment, allowing the individual to be comfortable while in the room. However, an occupancy sensor can also be used as a security measure.

With some monitoring systems, the occupancy sensor is configured to trigger surveillance cameras to display images of the area, making it possible for security personnel to view whomever has entered a given chamber or space.

While many people think of an occupancy sensor as controlling lights along with heating and cooling equipment, sensors of this type can do a lot more.

In like manner, the sensors can power up equipment when anyone enters the space, then power down that same equipment when the space is unoccupied.

Photoelectric Effect

When matter is struck by electromagnetic waves with relatively short wavelengths, such as ultraviolet light or visible light, its atoms can emit electrons. This process is known as the photoelectric effect or, less commonly, the Hertz effect, and it occurs because electromagnetic waves possess energy that is capable of dislodging the electrons in an atom.

Light, it was discovered, can act both as a wave and as a particle; light travels in wave motion but can physically impact surfaces and even cause mechanical change by dislodging electrons from atoms.

The number of electrons ejected as a result of the photoelectric effect is closely related to the frequency and the intensity of the light shone on the metal surface.

Low frequency light, which has a long wavelength , tends to dislodge few, if any, electrons from a metallic surface. This is true if the light is of high intensity or low intensity.

At high frequency, however, light tends to dislodge far more electrons, especially if the light is particularly intense. This basically means that, at any intensity, red light will release very few electrons but blue light will dislodge many.

It also supported the wave-particle duality theory of light at a time when most scientists believed that light behaved as either a particle or a wave, not both.

Quanta of light strike and dislodge electrons when light is shone on a metallic surface; this is the photoelectric effect.

Optical Coherence Tomography

Optical coherence tomography (OCT) is a procedure used for the noninvasive examination of intraocular structures. Primarily used for analysis of the retina and optic nerve, OCT centers on the amount of light absorption or scattering that occurs when light passes through a given tissue layer. Optical coherence tomography uses a diode laser, which emits light at a wavelength of about 840 nanometers. Two beams of light, a reference beam aimed at a mirror and a detection beam aimed at the eye tissues, are compared, measured, and analyzed. OCT allows physicians to develop cross-sectional images of the anterior chamber of the eye as well as three-dimensional images of the retina.

OCT images enable physicians to detect anatomical alterations in the ocular structures that occur with glaucoma and retinal disease. Ophthalmologists can determine the overall retinal thickness as well as the thickness of individual layers of the retina to identify macular swelling, macular degeneration, and macular holes. They can easily recognize epiretinal membranes on the retinal surface. Furthermore, optical coherence tomography facilitates the evaluation of the horizontal and vertical cup to disc sizes for long-term tracking of glaucoma damage.


Barriers to achieving satisfactory optical coherence tomography scans include cloudiness of the cornea or lens, lack of patient cooperation, and excessive blinking. The OCT device obtains approximately 27,000 scans per second, allowing increased resolution and detail with a minimal amount of time required. Although it is possible to obtain high-quality scans through a small pupil, sometimes the pupils must be dilated. It is also useful for the patient to use artificial lubricants on the surface of the eye before the examination.

Examination with optical coherence tomography scans often provides valuable information regarding structural abnormalities. For example, subretinal tumors, such as melanomas, may raise the entire retina, producing an upward bowing of the retina visible on the OCT. An epiretinal membrane will show up as a bright line overlying the retina with wavy folds underneath the line, due to lateral traction on the retinal surface by the membrane. A full-thickness macular hole will appear as an obvious discontinuity in the retina at the macula with pockets of fluid in the adjacent retina.

Trigger Point

A trigger point is an area of bunched muscle fibers that are localized to a small region.

Practitioners of trigger point therapy believe that these points can cause pain both in the area of the trigger as well as in other parts of the body. This is often called referred pain.

Generally trigger points are thought to cause pain that cannot be explained through other means. Although many people believe that trigger points are a source of pain, there is little scientific evidence backing it.

If the trigger point is pressed then it may also induce the same pain that the patient suffers from. Although the trigger site method is used by a large number of different practitioners including massage therapists and chiropractors there is still no formal way of defining it. This is one of the reasons why many medical professionals are hesitant to take the therapy seriously.

Myofascial pain syndrome is the main theory behind trigger point therapy. This syndrome occurs when hyperirritable spots affect functions of the central nervous system.

The pain that occurs as a result of this is thought to arise because of trigger points.

Self treatment usually involves using the elbow or knee to press on the points as the fingers can get tired relatively quickly. Although in general treating a trigger point in order to try to reduce pain is safe, there are some situations where it may not be advisable.

Torque Sensor

In the sensor, a metal spring is attached to a strain gauge , which is affected by the torque the sensor is exposed to.

A torque transducer is usually classified as either a rotary or reaction sensor and its function is dependent on how much torque it can handle, what kind of load and drives it is built for, and the load it can tolerate when a machine or engine is started.

The reaction type of torque sensor is stationary and requires a way to attach electronics and electrical connections to the moving components being measured.

More stable systems have a rotary torque sensor, in which the sensor electronics rotate with the sensor.

Measurement errors caused by the force of mechanical components affect the accuracy of a torque sensor attached in-line.

Load forces of fan or blower, conveyor or crane, to crushing equipment and crankshafts of automobile engines are rated in a scale to categorize each torque sensor.

A torque sensor can handle a certain drive force created by the particular engine type.

Optode

An optode is an optical sensing device capable of measuring many aspects of a substance — commonly airborne or submerged — if a user points the device at the substance.

Three parts are required to make an optode work; one is a polymer that captures the substance to be measured.

A chemical or energy signal is applied to the captured substance to cause a reaction, based on what is being measured.

For a reaction to occur, the optode must first capture a substance. This can be done by pointing the device at a substance, but this is unreliable.

After the substance is captured, another substance must be exposed to it to cause a reaction. This second substance is determined by what the optode measures and what the captured substance is.

Some optodes may skip a reacting substance in favor of using an energy or light source that will cause a reaction based on the amount of energy, though these units are uncommon.

An optode is capable of measuring many substances and reactions, but the most common measurement is light-based.

Light Detector

A light detector is a device or device component that is used to recognize the presence of light, often with the goal of initiating a process in response to light.

A light detector in such a device recognizes the presence and intensity of light and initiates a process that changes the screen brightness for ease of viewing.

One light detector may, for instance, be made to detect any light at all while another may only detect certain colors.

Light detectors are often designed to detect and respond to very different levels of light intensity as well.

A cryogenic light detector, for example, is intended to detect and measure the energy of individual photons while many detectors for personal use only respond to light that is, by comparison, very intense.

It is not uncommon for an outdoor light, for instance, to have a light detector that enables it to automatically turn on or off based on the presence of light. Likewise, a camera might incorporate a light detector that automatically determines whether or not to activate the flash.

More complex robots may use light detectors to guide them to fires or to other specific sources of light.