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K-30 CO2 Sensor Troubleshooting with Arduino or Raspberry Pi
Customers using SenseAir's K-30 CO2 sensor with an Arduino micro controller or the Raspberry Pi may see the sensor "lock up" during use. Here's how to fix it.
How to Fix GasLab® Software Not Detecting Your CO2 Sensor
Having trouble connecting your CO2 sensor to GasLab® Software? Learn how to fix driver issues, install the correct FTDI USB-to-UART drivers, and restore communication.
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.
Click here to read or download the app note (pdf).
Note that like CO2 sensors, oxygen sensors are also pressure and altitude dependent. We had a client in Bangalore, India purchase a CM-0505 O2 Data Logger. He reported that it was reading 18.3% instead of the expected 20.9% when exposed to outdoor ambient air.
I looked up the Bangalore, India Airport information and found that the altitude was 2,890 feet above sea level. Using this chart we found online, we were able to confirm for the client that in fact, his meter was performing within the expected tolerances.
Measuring CO2 in Exhaled Breath to Help Save Lives
Capnography is the measuring and monitoring of the carbon dioxide levels in exhaled breath. In healthy individuals, the difference between the CO2 exhaled and CO2 levels in arterial blood are proportional. Therefore, by monitoring the waveform of CO2 levels on a capnogram (an electronic capnography monitor) over time, medical personnel like anesthesiologists or paramedics can use the information to monitor a patient. Sudden changes in end-tidal CO2 (ETCO2, the level of carbon dioxide released at the end of expiration) may signify changes in a patient’s heart or lung functions.
Non-dispersive infra-red (NDIR) CO2 sensors are at the heart of virtually every capnogram. Their small size and relatively fast response time make them perfect for portable devices.
For example, our SprintIR 20Hz CO2 sensor has set a new benchmark as the fastest, most accurate CO2 sensor on the market. Capable of taking up to 20 readings per second, it is up to 10 times as fast as competing products. Medical equipment manufacturers worldwide are evaluating this sensor to use in their next generation of products.
And while capno-grams are used by anesthesiologists and EMS personnel today, even more exciting uses as clinical evaluation tools are being tested. Capnography may help to test for asthma, heart failure, diabetes, and more.
