Since Joseph Black, a Scottish chemist and physician first identified carbon dioxide in the s, scientists have looked for a way to measure this common gas. One of the earliest CO2 measurement devices was a mercury manometer. Manometers use a U-shaped glass tube filled with mercury to measure gas pressure. While mercury manometers can be very accurate, the procedure for measuring CO2 levels in air samples can take hours.
The original Applied Physics Corp. Infrared Gas Analyzer operated on Mauna Loa from until It has an infrared light radiation source at one end of a gas sample tube and an IR detector at the other. The band of infrared radiation is very close to the absorption band of CO2. As a result, the amount of light radiation that is absorbed by the CO2 molecules is proportional to the amount of carbon dioxide in the gas sample.
However, since low levels of CO2 do not absorb much light, a long tube is needed before the effect can be measured. While the original IR gas analyzer was accurate, it was bulky.
The sample tube alone was 40cm 16 inches long. The challenge is getting the right balance. Engineers use a longer optical path to measure lower levels of CO2 more accurately - which means a larger gas sample chamber.
On the other hand, in ambient air environments - such as schools, offices, and homes - the demand is for ever-smaller sensors to fit neatly inside compact devices. These sensors solved the size problem by using folded optics and metalized molded plastic to reflect the light through a curved shape referred to as a 'waveguide' that was longer than the footprint of the sensor module.
The highly reflective coating ensured that the CO2 molecules inside the gas sample chamber would absorb the same amount of light as traditional straight-path design. By using advanced optics, new waveguide designs allowed for progressively smaller sensors with increased sensitivity. This sensor was used for many years in OEM consumer safety products. Today's newest generation of CO2 sensors has even more optimized waveguides, allowing a longer optical light path to be folded into an even smaller.
In addition to a smaller size, new mid-range infrared light-emitting diode LED light sources have been developed that allow NDIR sensors to operate at much lower power levels. Combined with a photo-diode light detector, these solid-state sensors also provide a much longer life-span. Gas Sensors types and mechanism. CO 2 Sensors. Types and Characteristics of Gas Sensors. Table 1. NDIR method. More information on the NDIR method is provided here.
What is NDIR? Semiconductor method. Electrochemical method. What makes Senseair different? World's smallest class current consumption High accuracy even in compact. For example, brewing and bottling can create vast amounts of CO2 from fermentation. Since CO2 is odorless and colorless, a slow leak into a confined area may not be detected before the atmosphere becomes deadly due to a lack of oxygen.
Without the right sensor, carbon dioxide levels in your facility could exceed the recommended threshold putting you and your employees at great risk. Learn more here. If a carbon dioxide gas buildup occurs in any area of an industrial facility or laboratory, it must be detected quickly. MOS carbon dioxide sensors use the resistivity of metal compounds to test the amounts of gas in the air.
For example, copper, which is used a lot in wiring, would be less resistant than rubber, which is used to stop electric currents. A MOS sensor has a metal strip or film that is exposed to the air being tested. This strip has a constant electric current running through it. As the air comes into contact with the piece, it will interact with the metal and change the chemical composition, either through a reduction or oxidation reaction. When this happens, the resistivity, or conductivity, of the metal will be altered.
The kind of resistance change, whether increasing or decreasing, and its magnitude, determines the concentration of the target gas. Based on what kind of metal it is, different gases will react to the strip. The case for using a CO 2 sensor is clearly strong. But when it comes to choosing the right one, there are a few things to consider:. While MOS sensors do very well in CO 2 levels above ppm, this level is already high enough to affect you. NDIR sensors are the longest-lasting monitor currently on the market.
While both electrochemical and MOS sensors have made considerable strides in this department, they are still behind the NDIR sensor type, which usually lasts years or more. Both MOS and electrochemical sensors can have something called cross-sensitivity bias.
When a substance other than CO 2 reacts in the sensor, such as water vapour, it changes the electrical properties of the sensor and the readings it gives you. This means the readings displayed on your CO 2 monitor can be significantly higher or lower than the true value. NDIR sensors are a very cost-effective solution. They are often much cheaper than other technology and can be operated using a battery or solar-powered.
This makes them easy to install and very low maintenance. Multi-sensors may be more expensive, but they can include CO 2 , temperature and humidity sensors all in one device, saving you money overall. Look for sensors that offer easy data integration and secure data transmission.
As technology advances, you can access multiple types of Indoor environment monitoring sensors for collecting data. Contact our IoT business development team to see how we can support you to keep your internal air quality at optimum levels.
Our wireless multi-sensors measure and monitor the carbon dioxide CO 2 levels, ambient temperature and relative humidity in a room or zone. The small wireless CO 2 sensors simply stick onto the wall and are solar-powered using ambient room light, making them easy to install and very low maintenance. Find out more. Our room condition sensor measures occupancy, light, sound, temperature and humidity. This small, discreet sensor can be mounted on a wall, ceiling or table top.
Producing near real-time, highly accurate data which you can use to ensure your room conditions are at optimum levels at all times. Our wireless multi-sensors measure the ambient temperature and relative humidity in each room, cabinet or zone. The small, solar-powered sensors use ultra-low-power wireless technology, making them easy to install and very low maintenance. Our wireless door and window sensors automatically detect open doors or windows around your building, including doors on cupboards, cabinets and fridges.
The small, solar-powered contact sensors use ultra-low-power wireless technology, making them easy to install and very low maintenance. Our wireless current sensors measure energy consumption at a circuit, zone or machine level, in real time.
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