High-Speed Sensors Provide Improved CO2 Response Time for Incubation

Incubation and CO2 Sensors

High-Speed sensors provide improved CO2 response time for Incubation applications

Partnered Article with Gas Sensing Solutions 

CO2 incubators are designed to mimic a cell’s natural environment and ensure conditions are constant. Although there are different types of an incubator, most are designed to control CO2, relative humidity, temperature, and pH at constant levels. New high-speed CO2 sensors are now available that allow designers to respond and manage gas levels with unprecedented fidelity.

What is an Incubator?

Micro-organism incubators are essentially ovens that are temperature-controlled, to work within a strict biological range, and are mainly used for cultivating and storing microbial culture. These incubators can be found in laboratories across the world and are an essential piece of equipment. Both medical and biological labs use incubators to provide the correct controlled environment for successfully growing cultures.

 

Incubator Block Diagram GSS

Why CO2 Needs to be Measured?

Cultures grown within incubators require very specific environmental conditions. Typically, incubators allow the user to monitor and adjust different factors such as temperature, relative humidity and carbon dioxide levels to control pH of growth medium to ensure optimal growing or storage conditions are maintained.

Cell growth is managed by controlling the pH value, which is typically in the range from 7.0 to 7.7. Chemical reactions within the medium can alter the pH.  In order to counter these reactions, levels of CO₂ are controlled, helping to maintain a steady pH equilibrium in the growth medium.

If there is not enough CO₂ in the atmosphere, CO₂ will outgas from the culture media, and the substance will become too alkaline; excessive CO₂ concentration in the atmosphere will cause more CO₂ gas to be absorbed by the mixture, leading to high acidity levels. Providing a controlled CO₂ atmosphere helps maintain the required concentration of CO₂ in the growth medium, stabilizing the resultant pH.

What are the requirements for the CO2 Sensor?

A CO₂ sensor used in a cell incubator should be responsive, accurate, and stable over time. Undesired changes within the incubator are likely to have a negative impact on the culture, and it is, therefore, vital to know when CO₂ levels have changed, as well as the extent of the variation and to be able to respond accordingly. Due to the high humidity environment, an action also needs to be taken to mitigate the effects of high humidity levels, particularly during the sterilization process. Condensation on the sensor will cause the sensor to report inaccurate results.

Having a fast CO₂ sensor that can detect a change in CO₂ gas levels enables adjustments to be made in near real-time, reducing the opportunity for the incubator environment to drift far from nominal.

NDIR CO2 Sensors

CO2Meter has partnered with Gas Sensing Solutions to provide their CO2 sensors which use a solid-state, LED light source. This type of light source has numerous advantages, particularly for applications that need high response times. The CO2 gas is strongly absorbed by mid-IR 4.25um light. GSS also manufactures its own LEDs, which have been specifically designed to emit a narrow band of light centered at 4.25um.

Furthermore, the sensors provide high speed and high response rates specifically targeted at applications that require near-real-time CO₂ measurement capability.

Introducing the SprintIR-6S and ExplorIR-W

The SprintIR-6S and ExplorIR-W series of sensors are a range of high accuracy carbon dioxide (CO2) sensors designed to meet the needs of customers who require fast measurement of CO2 levels. The sensors are designed to take a reading 20 times a second for the SprintIR-6S and 2 times a second for the ExplorIR-W.  The optical cavity has been designed along with a flow port adaptor to enable gas to flow through the sensor at high speed, enabling the user to make use of the very high measurement rate capability.

The flow port adaptor has been designed to allow CO2 gas to be exchanged inside the gas measurement chamber.

 

Sensor Cap Diagram

Rendering by Ben Santiago
Both series of sensors are available with CO₂ concentration ranges from 0-5%, up to 0-100%. They feature a typical measurement accuracy of 70ppm and have built-in auto-zeroing, ensuring excellent long-term accuracy.
Incubator Timing Diagram
In most applications, with a measurement rate of up to 20Hz, the ability of the sensor to provide real-time readings will be limited by the flow rate through the sensor. The most important factor is the gas exchange rate. This is the amount of time it takes for the gas to enter the CO2 measurement chamber, get measured, and then replaced.
The sensor has a gas measurement chamber volume of approximately 2.8ml.  As a rule, to properly exchange the gas in the chamber, there needs to be an x5 volume of gas passed through the sensor. Therefore, approximately 14ml of gas needs to flow through the sensor for each reading to be effective.
Max Flow Rate
The maximum flow rate supported by the SprintIR-6S is approximately 19ltr/minute CO₂ before the sensor is unable to track the gas flow.

Conclusion

The SprintIR-6S and ExplorIR-W CO₂ sensors have been specifically designed to address applications where high measurement rate, responsiveness, and long-term accuracy are paramount. These sensors are furthermore suitable and easily integrated for CO2 incubators and a variety of other life science applications. They both come with several options that allow the sensor to be optimized for the installation process.

About GSS

Headquartered in the UK, Gas Sensing Solutions is a global leader in solid-state Non-Dispersive Infra-Red (NDIR) LED-based gas sensors.  Uniquely, the LEDs and companion photodetectors are manufactured in-house on molecular beam epitaxy (MBE) machines and used in all its patented NDIR diffusion CO2 sensors.

GSS design, develops and manufactures a wide range of solid-state NDIR CO2 gas sensors, providing innovative products to the world’s leading OEMs where low power, high accuracy, and high-speed measuring capability are required.  GSS has world-wide representation, selling into a wide range of markets including indoor air quality monitoring systems, healthcare, aerospace, food storage, transport and packaging, and personal safety equipment.

Visit the GSS website to learn more about their technology and high-speed sensors.


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