CO is colorless and odorless gas, which is difficult to feel and smell. But it will be very dangerous if the person falls into the CO, even worse, it can threaten our life safety. In the room temperature, the CO is easy to shape the explosion mixture mixing with the air, once touching the open flame and high temperature, it will result in the burning and explosion. CO belongs to the flammable and explosive gas.
When the fire happens, especially the early stage of fire, there a large amount of CO in the fired building. The CO will directly threaten the life safety of persons in the fired building and the firemen, who is entering the fired building to save the person life. In order to detect the CO in a real time, it is essential to equip the CO detector or alarming device built-in CO sensor in the fired places.
As the core element in the CO detection device, how can we choose the suitable model? Different models, there are different principles.
Working principle: The gas sensitivity of semi-conductor sensor is based on the heated temperature of sensitive elements. The sensitive element will be heated to below 100℃。 This temperature is lower than other detection temperature for other gas, such as Butane, methane, hydrogen, ethanol vapor. Under the low temperature, the response speed will be decreased and its sensitivity is easy to be affected by water vapor.
In order to solve this above issue, the sensitive element will be heated alternately from high to low temperature. During the high temperature heating, the water vapor and other mixed gas will be removed out from the sensitive elements surface. Under the low temperature heating, the sensitive element can detect the CO and features excellent sensitivity and repeatability.
Advantage: Low price and good performance
Disadvantage: High power consumption, not powered by battery, easy to be affected by temperature, humidity and airflow, bad anti-cross interference, high false alarming rate.
The electric current is proportional to the CO concentration. And the output signal of CO sensor has the excellent linear relationship with CO concentration. Features good signal processing and convenient display. Under the room temperature, CO sensor can make the response, it not need the heater, which is powered by battery.
Obviously, the high gas selectivity of electrochemical sensor will reduce the effect of interfering gases.
Advantage: Small volume, low power consumption and high sensitivity, good reliability and linear performance, excellent repeatability, short response time, long service time and its resolution can reach 1ppm。
Disadvantage: There are large distinguish on the price, performance, craft, anti-interference, temperature and humidity.
3.NDIR Infrared Principle
Molecules composed of two different types of atoms have dipole moment (that is the multiply value of the length of the dipole and the power on one end of the dipole). When the gas is irradiated with infrared light, it will absorb the specific wavelength of light determined by the gas molecule structure.
To judge the gas type through the absorption wavelength from absorption spectrum, to detect the gas concentration through the absorption strength. NDIR Gas sensor features high sensitivity, good selectivity and high precision, which usually apply for the instrument because of its complex structure and high cost, not available in alarming device.
Advantage: Wide detection range, high precision, good selectivity and high reliability, no absorption, no poisoning and no depending on Oxygen and small influence on environment interference and long serving life.
Disadvantage: High price, difficult maintenance, large volume, not suitable to portable device, low precision for low concentration detection, not available to charge for a long time.