Sensor Calibration

By Madison Denardo - September 20, 2021

Life safety and increased crop yield are at the center of why annual CO2 sensor calibrations are so important. Let’s break down what goes into a proper sensor calibration. 

What is being measured?

A CO₂ sensor installed as part of a commercial office building measures CO₂ levels for comfort in ranges from 350ppm to about 450ppm. Outside air is about 400 ppm and a maximum indoor comfort level is about 1,000ppm.

A CO₂ sensor installed as part of an indoor agricultural enrichment system will be measuring a higher and wider range of CO₂ levels, not only for effective enrichment, but also for life safety. Therefore, the sensor must have a wider range of sensitivity. A level of CO₂ of 1500ppm is the average for an enriched crop environment. Sensors used in this environment must not only detect the most accurate enrichment levels, but also must activate horn/strobe when levels are dangerous. The maximum safe level of CO₂ exposure in an industrial environment is 5,000ppm over an eight-hour period, according to OSHA. The Universal CO2 Monitoring System adheres to local and national fire code. Building occupants are alerted to CO2 levels greater than 5,000ppm which gives your employees ample time to move to a safe location and attempt to identify the cause of the gas accumulation. At this alarm level, the safety valve closes. This will prevent the build-up of more CO2. Universal CO2 supplies and installs a variety of sensors that have a range from 5,000 to 50,000 ppm spans, depending on code requirements.

What can cause inaccuracy of CO2 sensors? 

  • The method of sensor calibration (field calibration versus auto-calibration, more on this in a bit) 

  • Frequency of calibration 

  • Quality of manufacturing  

  • Environmental factors 

  • Exposure to water and airborne pollutants 

  • Harm to the sensor

Are my CO₂ sensors accurate?

Not all sensors are created equal. Self-calibrating sensors were initially developed for office environments and do not adapt well to the grow space, which can lead to counterproductive behaviors. They automatically calibrate by comparing themselves with ambient atmospheric conditions, which are very different from the artificial environments created in a cultivation facility. Depending on your local air quality, temperature, pressure, elevation, etc. these sensors have the potential to distort gas readings within your facility thus driving up or down your CO2 ppm and ineffectively maintaining your grow room CO2 levels. Have you ever wondered why your crop yield isn’t what it used to be? 

Universal CO2 supplies and installs high quality, field calibrated CO₂ sensors that have been tested by our trained engineers to provide our customers with the utmost accurate enrichment via systems that are code compliant and safe for working conditions. Our calibration process tests the sensor against up to three different laboratory grade reference gases certified at specific ppm levels to accomplish a true and accurate calibration. 

Accuracy is determined by repeatedly testing the sensor against a reference gas with a known ppm value. All readings are recorded, and then the range of readings defines the sensor's accuracy. 

How do I know if my sensors need calibration?

Depending on the sensor manufacturer specifications, most CO2 sensors need calibration one to two times per year. Also, your system and facility will tell you. Are you gassing more than usual? Is your crop yielding less than the typical amount? Are your rooms alarming for no apparent reason? If the answer to any of these questions is “Yes” then the first place to start to remedy these situations is a sensor calibration. 

No matter the location of your facility, Universal CO2 can provide you high quality sensors and calibration solutions. 

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