Smoke detector working principle

The most widely used smoke detectors are photoelectric and ionization smoke detectors

Photoelectric smoke detector

This works on the principle of light scattering principle.the smoke sensing chamber contains an IR led source with a peak spectral emission of 880 nm .This source is placed at an angle of from a spectrally matched photo diode receiver During a no smoke condition,only light reflected from the chamber walls enter the receiver and shows up as a small photo current.

pe sd theory

As the smoke particles enter the sensing chamber  and cross the light beam of LED more light reaches the receiver due to scattering.The receiver circuitry converts this photo current into a signal voltage.In a detector when this voltage reaches a preset level an alarm is produced.In a sensor this signal voltage goes into an 8 bit A to D converter A digital representation of this signal voltage is then transmitted to the fire alarm panel for further  processing

photo electric sd

Ionization Smoke detector

This device use a small radiation source, Americium 241 which emits alpha particles that ionize air molecules between two electric allies charged electrodes.With the application of a DC volt. to these electrodes, a small ionization current flows within the chamber .

io sd

As the smoke enters the chamber a decrease in ionization current results .This current is converted into a signal voltage by a trans impedance circuit.In a detector when this signal voltage drops below a preset level an alarm is produced In a sensor this signal voltage goes into a 8 bit A/D C .A digital representation of this signal voltage is then transmitter to FAP for further processing

ionisation smoke detector

To learn more about Instrumentation and Control, purchase your copy now

from amazon

Or

Basic Instrumentation and Calibration

24 thoughts on “Smoke detector working principle

  1. Pingback: My Post till now | Kishore Karuppaswamy

  2. Pingback: All my posts till now | Kishore Karuppaswamy

  3. Pingback: A typical Foundation Field bus wiring diagram | Kishore Karuppaswamy

  4. Pingback: Instrumentation related to a motor driven pump | Kishore Karuppaswamy

  5. Pingback: Dampers | Kishore Karuppaswamy

  6. Pingback: I/P Converter | Kishore Karuppaswamy

  7. Pingback: Calibration of Temperature transmitter zero trimming | Kishore Karuppaswamy

  8. Pingback: Calibration of siemens sipart PS2 | Kishore Karuppaswamy

  9. Pingback: Temperature transmitter – RTD | Kishore Karuppaswamy

  10. Pingback: Painting Procedure | Kishore Karuppaswamy

  11. Pingback: Instrumentation Cable design specification | Kishore Karuppaswamy

  12. Pingback: Acceptable accuracy ranges of Instruments | Kishore Karuppaswamy

  13. Pingback: Standard Power supply requirements for Instrumentation devices | Kishore Karuppaswamy

  14. Pingback: General design requirements of Instrumentation part 2 | Kishore Karuppaswamy

  15. Pingback: General design requirements of Instrumentation part 3 | Kishore Karuppaswamy

  16. Pingback: AK ENCON ENGINEERING SERVICES | Kishore Karuppaswamy

  17. Pingback: Bastard Esterraj Stephen and MC GSN Raju | Kishore Karuppaswamy

  18. Pingback: Ultrasonic flow measurement working principle | Kishore Karuppaswamy

  19. Pingback: Boiler | Kishore Karuppaswamy

  20. Pingback: General design requirements of Instrumentation part 5 | Kishore Karuppaswamy

  21. Pingback: All my posts till now | kishore koduvayur

  22. Pingback: AS-i (Actuator sensor-Interface Protocol) | Kishore Karuppaswamy

  23. Pingback: Profibus | Kishore Karuppaswamy

  24. Pingback: Flow transmitter DP type | Kishore Karuppaswamy

Leave a Reply