Photoelectric and Ultrasonic Devices 365

alkali

A non-acidic substance that dissolves in water and increases the pH of a solution. Alkalis can form corrosive salts.

blind zone

An area directly in front of the sensor face in which objects cannot be detected because they are too close.

convergent beam scan

A photoelectric scanning technique in which a position sensor detector mounted on the receiver measures the angle of light as it bounces off the target and uses this information to suppress backgrounds beyond a specified distance.

dark operate mode

A photoelectric scanning mode in which a target is detected when light is blocked from the receiver.

diffuse mode

An ultrasonic sensing mode in which the emitter bounces a sound wave off a target. Diffuse mode is the standard mode of operation for ultrasonic sensors.

diffuse scan

A photoelectric scanning technique in which a small amount of light is transmitted toward a target and the scattered reflected light is used to detect presence.

direct scan

A photoelectric scanning technique in which a beam of light shines directly from the transmitter to the receiver. An object is detected when it passes between transmitter and receiver and blocks the beam of light.

electromagnetic interference

The disruption of transmission or reception of a signal caused by electrical and magnetic fields.

emitter

A fiber optic cable that transmits a beam of light.

excess gain

The additional amount of light required by a sensor in a contaminated environment to achieve the same level of detection as in a clean environment.

eye

The window or lens of a photoelectric sensor.

fiber optic cable

A cable packed with thin, flexible glass or plastic optical fibers that transmit light instead of electricity.

hydraulic fluid

A viscous liquid, typically oil, used in industrial applications.

infrared light

An area outside of the visible part of the color spectrum, beyond red. Infrared is often used for an invisible wireless connection between devices, like TV remote controllers.

light emitting diode

A semiconductor device that emits a narrow spectrum of light in a forward direction. Also known as LED.

light operate mode

A photoelectric scanning mode in which a target is detected when light from the transmitter reaches the receiver.

load current

The current drawn by a sensor when it is energized. Most photoelectric sensors cannot handle more than .5 amps of current.

load-powered

Drawing operating current through a load.

minimum holding current

The amount of current required for a photoelectric sensor to operate. Most photoelectric sensors need a minimum current of 3 mA to 20 mA in order to function properly.

mutual interference

Interference between two sensors when the signal from one sensor is unintentionally picked up by another sensor nearby. Mutual interference can cause poor sensor performance or false outputs.

N-doped

Silicon that has been given a negative charge through the addition of other substances.

NPN transistor

A transistor with one layer of positively charged semiconductor material between two negatively charged layers.

off-state leakage current

Also known as load current and residual current. The amount of current required to keep a sensor active when it is not detecting a target.

operating current

Also known as off-state leakage current and residual current. The amount of current required to keep a sensor active when it is not detecting a target.

organic solvent

Solvents that are organic compounds and contain carbon atoms. The most common organic solvent is water.

P-doped

Silicon that has been given a positive charge through the addition of other substances.

photoelectric sensor

A type of sensor that detects the presence of an object through the use of a beam of light. Photoelectric sensors have an extremely broad sensing range, from a few millimeters to 100 feet away.

photoreceiver

The part of a photoelectric sensor that detects a beam of light. The phototreceiver may be in a separate unit, or enclosed in the same unit as the phototransmitter.

phototransmitter

The part of a photoelectric sensor that emits a beam of light. The phototransmitter may be in a separate unit, or enclosed in the same unit as the photoreceiver.

PNP transistor

A transistor with one layer of negatively charged semiconductor material between two positively charged layers.

polarized scan

A photoelectric scanning technique that uses special filters to absorb glare and reduce or eliminate reflections. Polarized scans filter out all unwanted light sources and detect only depolarized light.

position sensor detector

A device mounted on a photoreceiver that determines the distance of a target by measuring the angle of light as it bounces off a target.

radial

Radiating outward in all directions from a common center.

receiver

A fiber optic cable that receives a beam of light.

reflective scan

A photoelectric scanning technique in which light from the transmitter bounces off a reflector placed outside of the housing and travels back to the receiver. Also known as a retroreflective scan.

reflectivity value

A numeric value signifying the amount of light reflected from an object. A white test card has a reflectivity value of 100%, while printed newspaper that absorbs light has a reflectivity value of 60%.

reflex mode

An ultrasonic mode of operation in which sound waves are transmitted toward a reflector and bounce back to a receiver. An object is detected when it passes between the sensor and reflector and blocks the sound waves.

residual current

Also known as off-state leakage current and load current. The amount of current required to keep a sensor active when it is not detecting a target.

retroreflective scan

A photoelectric scanning technique in which light from the transmitter bounces off a reflector placed outside of the housing and travels back to the receiver. Also known as a reflective scan.

scanning

The process of detecting changes in the intensity of a beam of light in order to sense an object. Scanning technique is determined by the distance and physical properties of a target.

semiconductor

Silicon crystal that is transformed from an insulator into a conductor. Semiconductors are not as conductive as other materials, such as copper.

silicon

A natural element that forms crystals easily and does not conduct electric current. This makes a silicon an insulator.

solid state relay

An electronic relay with no moving parts.

solid state relay

An electronic switch that contains no moving parts. Solid state relays are rapidly replacing electromechanical relays.

specular scan

A photoelectric scanning technique in which light from the transmitter bounces off a shiny object and travels up to the receiver at exactly the same angle.

switching zone

The area the target must enter in order to be detected. The switching zone is determined by the diameter of light emitted from the transmitter.

target

The object or property being detected by a sensor.

thru-beam mode

An ultrasonic sensing mode in which the transmitter sends a sound wave toward the receiver. An object is detected when it passes between the transmitter and receiver and blocks the sound waves.

thru-beam scan

A photoelectric scanning technique in which a beam of light shines directly from the transmitter to the receiver. An object is detected when it passes between transmitter and receiver and blocks the beam of light.

thyristor

A solid-state switching device for semiconductors to convert AC current in one of two directions controlled by an electrode.

transistor

A device used to amplify a signal or open and close a circuit.

triac

An electronic switch that allows small control voltages and currents to switch very large voltages. Triacs conduct in either direction.

ultrasonic sensor

A type of sensor that uses sound waves to detect a target. Ultrasonic sensors are the best type of sensor for detecting liquids, clear objects, or irregularly shaped objects.

viscosity

A fluid's resistance to flow. Viscosity is used to describe friction of fluid.

white light

Light containing equal amounts of the primary colors. The human eye sees this light as colorless. Sunlight is white light.