When smoke enters the space between the electrodes, the conductivity of the ionized air changes, which causes the alarm to sound. In ionization detectors, which are the typical battery-powered detectors found in homes, a small radioactive source (usually Americium) ionizes the air between a pair of electrodes. In this case the photodiode is the transducer. When smoke enters the space between the LED and the photodiode, the photocurrent decreases, which sets off an alarm.
The photodetectors consist of a light source, such as a light-emitting diode (LED) and a photodiode to produce a current proportional to the intensity of light from the LED. Smoke detectors are of two types: photodetectors and ionization detectors. The detector in a spectrograph is a photographic film or plate. The information processor in a visual color measuring system is the human brain. The most common input transducers convert chemical or physical information into a current, voltage, or charge, and the most common output transducers convert electrical signals into some numerical form.
Skoog/Holler/Crouch Principles of Instrumental Analysis, 6th ed.Ī transducer is a device that converts chemical or physical information into an electrical signal or the reverse.
