Electrochemical Sensors for Gas Detection Instruments
A significant portion of its flammable, toxic and hazardous gases are electrochemically active and can be electrochemically oxidized or reduced. Utilizing these reactions, gas components can be distinguished and gas concentrations can be detected. Electrochemical gas sensors are divided into many subcategories:
(1), primary cell-type gas sensors (also known as: Gavony battery-type gas sensors, also known as fuel cell-type gas sensors, also known as spontaneous battery-type gas sensors), their principle is the same as the dry cell battery we use, except that the battery's carbon-manganese electrodes are replaced by gas electrodes. Taking the oxygen sensor as an example, oxygen is reduced at the cathode and electrons flow through the ammeter to the anode, where the lead metal is oxidized. The magnitude of the current is directly related to the concentration of oxygen. This type of sensor can effectively detect oxygen, sulfur dioxide, chlorine, and so on.
(2), constant potential electrolytic cell type gas sensor, this sensor is used for the detection of reducing gases is very effective, its principle is not the same as the primary cell type sensor, its electrochemical reaction occurs under the compulsion of the current, is a true Coulomb analysis of the sensor. This sensor has been successfully used for: carbon monoxide, hydrogen sulfide, hydrogen, ammonia, hydrazine, and other gases in the detection, is the mainstream of the existing toxic and hazardous gas detection sensor.
(3), concentration difference battery type gas sensor, with electrochemical activity of the gas on both sides of the electrochemical battery, will spontaneously form a concentration difference electric potential, the size of the electric potential and the concentration of the gas is related to the success of this sensor is the automobile oxygen sensor, solid electrolyte carbon dioxide sensor.
(4), limit current type gas sensor, there is a measurement of oxygen concentration of the sensor using the electrochemical cell in the limit current and carrier concentration related to the principle of preparation of oxygen (gas) concentration sensor, used for automotive oxygen detection, and oxygen concentration detection in steel.
Infrared
Most gases have characteristic absorption peaks in the mid-infrared region, and the concentration of a gas can be determined by detecting the absorption at the location of the characteristic absorption peak.
These sensors used to be used in large analytical instruments, but in recent years, with the development of the sensor industry based on MEMS technology, the size of these sensors has been reduced from a giant 10 liters and 45 kilograms to about 2 milliliters (the size of a thumb). The use of infrared detectors that do not require a modulated light source makes the instruments completely maintenance-free with no mechanical moving parts. The infrared gas sensor can effectively distinguish between gas types and accurately measure gas concentrations.
This sensor is successfully used for: carbon dioxide, methane detection.
