LOGICAL SENSOR pdf

EEEF DIAE LOGICAL SENSOR Topics Sensor wiring, switchs, TTL, sinking, sourcing Proximity detection, contact switch, photo optic, capacitive sensor, inductive and ultrasonic sensor Objectives Understand difference types of sensor output Know basic sensor types and understand applications issues EEEF DIAE LOGICAL SENSOR Sensor Introduction  Sensors allow a PLCs to detect a state of process.  Logical sensors can detect a state that is either true or false  Physical Phenomeno that are typical detect are listed below Inductive proximity: is a metal object near by? Capacitive proximity: is a object near by? Optical present: is an object breaking light beam or reflecting light? Mechanical contact: is an object touching a switch? EEEF DIAE LOGICAL SENSOR Sensor introduction  Sensors detect logic change and signal that change to the PLC.  Sensors switch a voltage or current on or of.  Sensors can switch directly load or eliminate plc operation.  Typical outputs of sensor are listed below Sinking or sourcing: Switches current on or of Plain Switch: Switches voltage on or of Solid state Relay: These switch ac output TTL: uses 0 or 5v to indicate logic levels EEEF DIAE LOGICAL SENSOR Sensor wiring Switches: Simple sensor, an example of switches and relay sensor wiring is shown in the figure below EEEF DIAE LOGICAL SENSOR Sinking/Sourcing sensor Sinking sensors allow current flow into sensor to voltage common. A NPN BJT is used for sinking sensor. Sourcing sensors allow current flow out of sensor from positive voltage. A PNP BJT is used for sourcing sensor. EEEF DIAE LOGICAL SENSOR Sinking/Sourcing Sensor EEEF DIAE LOGICAL SENSOR Sinking/Sourcing Sensor wiring. A NPN or PNP sensor output is cable of handing current up a few amps. NPN or PNP sensor output can switch loads directly Note: Always check document for rated voltages or currents EEEF DIAE LOGICAL SENSOR Connecting Sinking/Sourcing Sensor to plc There are two viable approaches to connect sensors to plc The first is to always use PNP sensors and the voltage input cards. The second is to use NPN sensors and voltage output cards EEEF DIAE LOGICAL SENSOR Connecting Sinking/Sourcing Sensor to plc EEEF DIAE LOGICAL SENSOR Connecting Sinking/Sourcing Sensor to plc [...]... (Photoelectric) Sensors Photoelectric sensors have been used for almost a century This sensors require light source(emitter) and detector(receive) Emitters produce light beams which is in the visible and invisible spectrum using LED or laser diode The emitter and detector are positioned so that an object is block or reflect a beam as present DIAE PRESENCE DETECTION EEEF Optical (Photoelectric) Sensors... DIAE PRESENCE DETECTION EEEF Capacitive Sensors Can detect most materials at distances up to a few centimeter This sensor can active output dependence on capacitive changes DIAE PRESENCE DETECTION EEEF Inductive Sensors Use a coil to generate high frequency magnetic field Use currents induced by magnetic fields to detect nearby objects By measuring inductance, sensors can detect magnetic objects nearby... (Photoelectric) Sensors Photoelectric sensors have been used for almost a century This sensors require light source(emitter) and detector(receive) Emitters produce light beams which is in the visible and invisible spectrum using LED or laser diode The emitter and detector are positioned so that an object is block or reflect a beam as present DIAE PRESENCE DETECTION EEEF Optical sensors have two operation mode:...PRESENCE DETECTION EEEF There are two basic way to detect object presence: Contact and Proximity Contact implies that there is mechanical contact between sensor an object Proximity indicates that the objects is near sensor but contact is not required DIAE PRESENCE DETECTION EEEF Contact switches There are two types of contact switches: normally open and normally closed Contact switches... objects By measuring inductance, sensors can detect magnetic objects nearby DIAE PRESENCE DETECTION EEEF Ultrasonic Sensors Emit sound above the normal hearing threshold of 16khz The sound travel to target and reflect proportional to the distance to the target Two common types of sensors are Electrostatic - use capacitive effect: has long range and wider bandwidth but more sensitive to factors as... has long range and wider bandwidth but more sensitive to factors as the humidity Piezoelectronic: base on charge displacement during strain in crystal lattices, these are rugged and inexpensive These sensors are very effective for several applications Fluid level in tank Crude distance measurement DIAE . levels EEEF DIAE LOGICAL SENSOR Sensor wiring Switches: Simple sensor, an example of switches and relay sensor wiring is shown in the figure below EEEF DIAE LOGICAL SENSOR Sinking/Sourcing sensor Sinking sensors. types of sensor output Know basic sensor types and understand applications issues EEEF DIAE LOGICAL SENSOR Sensor Introduction  Sensors allow a PLCs to detect a state of process.  Logical sensors. sensor. EEEF DIAE LOGICAL SENSOR Sinking/Sourcing Sensor EEEF DIAE LOGICAL SENSOR Sinking/Sourcing Sensor wiring. A NPN or PNP sensor output is cable of handing current up a few amps. NPN or PNP sensor output