--- title: How Gas Analysers Measure: Technologies and Gases url: https://www.sarveshanalytics.com/learn/track-measurement-principles.html description: How electrochemical, paramagnetic, zirconia, NDIR and thermal conductivity analysers work, how moisture is measured, and how to measure O2, H2, CO, CO2 and CH4. updated: 2026-11-03 source: html --- Learn ยท Track 2 of 8 # Measurement principles How each technology works, where it fails, and how each common gas is measured. 15 lessons About 52 min ## What this track covers No single sensor suits every gas. This track explains each principle in plain terms, compares them fairly, and then goes gas by gas so you can pick the right method for oxygen, hydrogen, carbon monoxide, carbon dioxide, methane and moisture. It ends with the choice every project faces: sample the gas and analyse it outside the pipe, or measure in place. ## Lessons, in order 1. [ **Gas analysis technologies compared: which sensor for which gas** Each gas analysis technology works only on gases with the right physical property: electrochemical and paramagnetic sensors for oxygen, zirconia for hot oxygen, NDIR for gases that absorb infrared (CO, CO2, methane), thermal conductivity for binary mixtures such as hydrogen in nitrogen, ceramic or chilled-mirror sensors for moisture. Beginner*3 min*](https://www.sarveshanalytics.com/learn/gas-analysis-technologies-compared.html) 2. [ **Electrochemical vs paramagnetic oxygen sensors** Electrochemical oxygen cells suit ppm and percent oxygen, are compact, and are consumed over time. Intermediate*4 min*](https://www.sarveshanalytics.com/learn/electrochemical-vs-paramagnetic-oxygen-sensors.html) 3. [ **How a zirconia oxygen analyser works** A zirconia analyser measures oxygen with a heated ceramic cell. Intermediate*4 min*](https://www.sarveshanalytics.com/learn/how-a-zirconia-oxygen-analyser-works.html) 4. [ **What is an NDIR gas analyser?** An NDIR (non-dispersive infrared) analyser shines infrared light through a sample and measures how much a target gas absorbs. Beginner*4 min*](https://www.sarveshanalytics.com/learn/what-is-an-ndir-gas-analyser.html) 5. [ **How thermal conductivity gas analysers (TCD) work** A thermal conductivity analyser heats a small element and measures how quickly the surrounding gas carries heat away. Intermediate*4 min*](https://www.sarveshanalytics.com/learn/how-thermal-conductivity-gas-analysers-work.html) 6. [ **What is dew point and how is it measured?** Dew point is the temperature at which moisture in a gas begins to condense. Beginner*4 min*](https://www.sarveshanalytics.com/learn/what-is-dew-point-and-how-is-it-measured.html) 7. [ **Moisture measurement methods compared for dry gas** Online dry-gas moisture is usually measured with a ceramic or capacitive sensor that responds to adsorbed water. Intermediate*3 min*](https://www.sarveshanalytics.com/learn/moisture-measurement-methods-compared.html) 8. [ **Cross-Sensitivity and interference in gas analysers** Cross-sensitivity is a sensor's response to gases other than its target. Intermediate*3 min*](https://www.sarveshanalytics.com/learn/cross-sensitivity-and-interference-in-gas-analysers.html) 9. [ **Trace oxygen measurement and air ingress: ppm done right** Air is 209,500 ppm oxygen, so a leak of just 0.01 % air adds about 21 ppm to a sample. Intermediate*4 min*](https://www.sarveshanalytics.com/learn/trace-oxygen-measurement-and-air-ingress.html) 10. [ **Measuring hydrogen: purity, mixtures and safety limits** Hydrogen purity and hydrogen in nitrogen or argon are measured by thermal conductivity, because hydrogen conducts heat about seven times better than most gases. Intermediate*3 min*](https://www.sarveshanalytics.com/learn/measuring-hydrogen-purity-and-hydrogen-in-gas-mixtures.html) 11. [ **Measuring carbon monoxide and carbon dioxide online** Carbon dioxide is measured by NDIR over ppm to 100 % ranges. Intermediate*3 min*](https://www.sarveshanalytics.com/learn/measuring-carbon-monoxide-and-carbon-dioxide.html) 12. [ **Measuring methane and biogas composition online** Methane and CO2 in biogas are measured by NDIR, separately or in one dual-channel analyser, and oxygen is measured to show air ingress. Intermediate*3 min*](https://www.sarveshanalytics.com/learn/measuring-methane-and-biogas.html) 13. [ **Extractive vs In-Situ gas analysis** In-situ analysers measure the gas where it flows, with no sample line, and suit hot, dusty ducts. Beginner*3 min*](https://www.sarveshanalytics.com/learn/extractive-vs-in-situ-gas-analysis.html) 14. [ **Choosing an oxygen analyser: trace, percent or purity** Choose by range. Beginner*3 min*](https://www.sarveshanalytics.com/learn/choosing-an-oxygen-analyser-trace-percent-or-purity.html) 15. [ **Why ambient pressure affects oxygen purity readings** Many oxygen sensors respond to the partial pressure of oxygen, which falls when barometric pressure falls even if the gas is unchanged. Intermediate*4 min*](https://www.sarveshanalytics.com/learn/why-ambient-pressure-affects-oxygen-purity-readings.html) Next track: [Sampling and conditioning](https://www.sarveshanalytics.com/learn/track-sampling.html)