**Please note that all CO2Meter operations will close starting at 3:00 pm et. Friday, April 19 in observance of the Easter holiday. All operations will reopen Tuesday, April 23 at 8:30 am et. All orders placed after noon et. on April 19 will ship on April 23. Thank you.**

News — K33

SenseAir CO2 Sensor Compares Favorably Against Vaisala CO2 Probe

A university study has found the SenseAir K-33 BLG 30% CO2 + RH/T and K-33 ELG 1% CO2 + RH/T data-logging environmental sensors gave similar results to a Vaisala CO2 Probe in both testing and real-world experiments. The study was conducted by a team of Environmental Engineering Researchers from the University of California, Merced. They were looking for a lower cost alternative to the Vaisala GMP343 Probe, a well-known brand of environmental sensor. Their goal was to develop a proof-of-concept for low-cost tools for long-term measurement and data logging of CO2 concentrations and fluxes in terrestrial ecosystems. In addition to costing less...

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Altitude Compensation for CO2 Sensor Modules

A customer called recently and said we had sold him a defective sensor module. He had calibrated it precisely at 0.0ppm (zero parts-per-million), took it outside, and the sensor read 335ppm. “Where do you live?” we asked. “Colorado,” he replied. It took a few minutes to explain, but in the end the customer understood that altitude makes a difference when you are measuring CO2 levels. CO2 sensor modules are calibrated at sea level, and are not designed to automatically compensate for changes to CO2 at higher altitudes. When you think about altitude, it helps to imagine a vertical column of...

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Senseair CO2 Sensor Pressure Dependence

All infrared (NDIR) CO2 sensors have a dependence on pressure. This is because of the physics principle used to measure CO2 concentration. The NDIR type of sensor measures the IR radiation absorbed by CO2 molecules, which corresponds to the mole concentration. When pressure increases, the number of molecules in a given volume also increases linearly. Conversely, when pressure decreases (higher altitudes, for example) the number of molecules decrease. This app note includes both general information about Senseair sensors and pressure, as well as the equation for computing true CO2 level readings at various pressures useful for any NDIR CO2 sensor....

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Calibrating SenseAir K33 Series CO2 Sensors

SenseAir K33 ELG, BLG or ICB CO2 sensors are pre-calibrated at the factory. During normal use, they are self calibrating using the ABC algorithm. If after rough transport or handling or for statistical purposes you want to re-calibrate these sensors, this document explains how using CO2 Meter's legacy DAS software as well as how to configure sensors, view data in real-time, or manage stored logs on sensors with internal memory. Note that you are encouraged to upgrade to the newer GasLab software which currently supports all K33 sensors. Download K33 Calibration Instructions (pdf).

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K-33 Host-Initiated Data Logging

sThe K‐33 ELG/BLG sensor can be used with the Sensor Development Kit and your PC to collect data. Under standard operating conditions the sensor will only take a measurement when data collection is enabled via the hardware jumper, however using the Start Measurement command and an extension to the MODBUS protocol we can manually initiate a reading from the sensor. Please read AN104 to understand the procedure behind accessing EEPROM and RAM with the MODBUS over UART protocol. Click here to download a zip file with documentation and source code.

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