What is the definition of "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.

Learn more about minimum holding current in the class Photoelectric and Ultrasonic Devices 365 below.


Motor Controls Training


Class Information
Motor Controls Training Tooling U-SME classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and will take approximately one hour to complete.
Class Name:Photoelectric and Ultrasonic Devices 365
Description:This class covers the properties and functions of photoelectric and ultrasonic sensors. Includes an Interactive Lab.
Prerequisites: 460210  460220 
Difficulty:Advanced
Number of Lessons:17
Language:English, Spanish
 
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Class Outline
  • Objectives
  • Photoelectric and Ultrasonic Sensors
  • Photoelectric Sensors
  • Fiber Optics
  • Direct and Retroreflective Scans
  • Polarized and Specular Scans
  • Diffuse and Convergent Beam Scans
  • Photoelectric Sensor Outputs
  • AC Outputs
  • DC Outputs
  • Photoelectric Sensor Range
  • Mounting Photoelectric Sensors
  • Ultrasonic Sensors
  • Ultrasonic Sensor Modes of Operation
  • Ultrasonic Sensor Range
  • Ultrasonic Sensor Applications
  • Summary
  
Class Objectives
  • Explain how photoelectric and ultrasonic sensors are used.
  • Describe how photoelectric sensors work.
  • Describe fiber optics technology.
  • Distinguish between direct and retroreflective scanning techniques.
  • Distinguish between polarized and specular scanning techniques.
  • Distinguish between diffuse and convergent beam scanning techniques.
  • Explain how photoelectric sensor outputs are used.
  • Describe AC outputs.
  • Describe DC outputs.
  • Describe factors that influence the sensing range of photoelectric sensors.
  • Explain how to mount photoelectric sensors.
  • Describe how ultrasonic sensors work.
  • Distinguish between the different operational modes of ultrasonic sensors.
  • Describe factors that influence the sensing range of ultrasonic sensors.
  • Describe how ultrasonic sensors are used in industry.

Class Vocabulary

Vocabulary TermDefinition
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 switch that contains no moving parts. Solid state relays are rapidly replacing electromechanical relays.
solid state relay An electronic relay with no moving parts.
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.