Introduction to sensors

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Introduction to sensors

  1. 1. Level I 1 Training Series: Level I
  2. 2. 2 Electrical InterfaceElectrical Interface The Back-end
  3. 3. 3 Electrical InterfaceElectrical Interface Divided into 2 areas: ◦ Operating voltage ◦ Output signal type Electrical Interface PowerPower SignalSignal
  4. 4. 4 OUTPUT SIGNAL TYPES  Discrete  ON or OFF  YES or NO  Analog  Speed control  Position information MIN MAX Electrical Interface SignalSignal
  5. 5. 5 OPERATING VOLTAGE  Direct Current (DC)  Current flows in only ONE direction  Safe, easy-to-handle power source  Alternating Current (AC)  Current changes direction 60 times a second  Readily available Electrical Interface PowerPower
  6. 6. 6 A DISCRETE SENSOR IS A SWITCH Electronics Sensing Side Front-end Electronics Power Wires Switch Electrical Interface
  7. 7. 7 Electronics BASIC SENSOR CIRCUIT Sensors with relay output + - Unlike a switch, sensors require power to operate Electrical Interface
  8. 8. 8 TYPES OF DISCRETE ELECTRICAL OUTPUTS  Sensors of today use Solid-State outputs, not mechanical relays Today Yesterday  PNP, 3-wire Relay  NPN, 3-wire  AC/DC, 2-wire Electrical Interface
  9. 9. 9 THE NPN & PNP OUTPUT Functions similar to a switch, But current only flows in one direction PNP Transistor Mechanical Switch Electrical Interface
  10. 10. 10 THE DIFFERENT TRANSISTORS What direction do you want current to flow? NPN Also called Sinking Electrical Interface PNP Also called Sourcing +--+
  11. 11. 11 PNP, 3-WIRE 1 4 + PNP Output 3 - Load Standard diagram form As shown in our catalog The Sensor The Load Connector Pins Electrical Interface
  12. 12. 12 PNP, 3-WIRE 1 4 + PNP Output 3 - Load Watching the current flow Sensors Power Output Signal Electrical Interface
  13. 13. 13 1 4 + NPN Output 3 - Load NPN, 3-WIRE Watching the current flow Sensors Power Output Signal Electrical Interface
  14. 14. 14 1 ~ 3 ~ Load THE 2-WIRE AC/DC OUTPUT Functions similar to a switch, But with a small leak Sensors Power Supply from leakage current Output Signal Triac Electrical Interface
  15. 15. 15 QUICK REFERENCE: WIRING PNP & NPN N P N P N P + - Load First side of load Second side of load Switched side Positive Negative Sensor is PNP Electrical Interface
  16. 16. 16 IF GIVEN A CHOICE, WHICH DISCRETE SENSOR TYPE SHOULD I CHOOSE? PNP or NPN, 3-wire - Fewer interface problems - Largest selection - Lowest unit costs AC/DC, 2-wire - Many interface issues - Smaller selection - Susceptible to noise 1st CHOICE 2nd CHOICE 1 4 + 3 - Load 1 ~ 3 ~ Load Electrical Interface
  17. 17. 17 NORMALLY OPEN (NO) VS. NORMALLY CLOSED (NC) Identifies the non-active state (target not present) of the sensor Electronics + - Normally Open Is it off (open)? Is it on (closed)? Electrical Interface
  18. 18. 18 NORMALLY OPEN (NO) VS. NORMALLY CLOSED (NC) Identifies the non-active state (target not present) of the sensor Electronics + - Is it off (open)? Is it on (closed)? Electronics + - Normally Closed Electrical Interface
  19. 19. 19 ANALOG OUTPUTS Unlike a discrete output with two defined states, analog signals have an infinite number of states. Discrete Analog On Off Voltage Time Max Min Voltage Time Electrical Interface
  20. 20. 20 ANALOG USES To provide absolute measurement or position information Measurement Position Electrical Interface
  21. 21. 21 ANALOG APPLICATIONS!  Spool diameter  Rotational position  Liquid level  Sort parts  Determine part orientation  Measure vibration  Measure straightness  Hydraulic or pneumatic cylinder position Expanding possibilities Expanding possibilities Electrical Interface
  22. 22. 22 ANALOG DATA 0 10987654321 Measurement Panel meters Control systems Electrical Interface
  23. 23. 23 ANALOG INFORMATION  The many forms for representing measurement or position information 10 0 10 -10 5 -5 20 0 20 4 Voltage Current Digital Pulse Electrical Interface
  24. 24. 24 ANALOG VOLTAGE Information contained in varying voltage Maximum Voltage 0 10 987654321 Measurement Half VoltageNo Voltage 0 10 987654321 Measurement 0 10 987654321 Measurement Water Analogy Volt Meter Electrical Interface
  25. 25. 25 ANALOG CURRENT Information contained in varying Current 0 10 987654321 Measurement 0 10 987654321 Measurement 0 10 987654321 Measurement Maximum CurrentHalf CurrentNo Current Water Analogy Current Meter Electrical Interface
  26. 26. 26 DIGITAL PULSE Information contained in digital pulse timing 100.00 Maximum measurementHalf wayMinimum measurement 50.000.00Pulse Width Meter Start/Stop Electrical Interface
  27. 27. 27 ELECTRICAL INTERFACE REVIEW  Operating voltage: Sensor Power DC: Safest AC: Most available  Output signal types Discrete  PNP, 3-wire  NPN, 3-wire  AC/DC 2-wire Analog  Voltage  Current  Digital pulse Electrical Interface PowerPower SignalSignal

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