PC-07Analytical · AT
Gas Analyzers & Sampling Systems
Online gas analysis for combustion control, process quality, emissions monitoring and inerting. An analyzer is only as reliable as the sample it receives — extraction, conditioning and integration are engineered with it.
01Scope
What's included
Online gas analyzers with sample extraction and conditioning.
- Oxygen analyzersZirconia in-situ probes for flue gas; paramagnetic analyzers for process and purity measurement.
- Infrared and multi-component analyzersNDIR analyzers for CO, CO₂, CH₄ and other infrared-active gases.
- Thermal conductivity and GCHydrogen and binary mixtures; process gas chromatographs for full composition.
- Laser and in-situ analyzersTunable diode laser analyzers across ducts and stacks for fast, selective measurement.
- Sample handlingProbes, heated lines, coolers, filters, pumps, analyzer panels and shelters.
02Compare
Measuring principles
The component, its concentration and the background gas decide the principle; the process conditions decide between in-situ and extractive.
| Principle | How it works | Suited for | Considerations |
|---|---|---|---|
| Zirconia oxygen | How it worksA heated zirconia cell generates a voltage from the difference in oxygen partial pressure between sample and reference air. | Suited forFlue-gas oxygen for combustion control in boilers, furnaces and kilns — often in-situ. | ConsiderationsThe cell runs hot, so combustibles in the sample react at it and lower the oxygen reading; not for flammable process streams. |
| Paramagnetic oxygen | How it worksOxygen is strongly paramagnetic; the analyzer measures its behaviour in a magnetic field. | Suited forPercent-level oxygen in process gases, inerting and purity measurement. | ConsiderationsNeeds a clean, dry, conditioned sample; some designs are sensitive to vibration and flow changes. |
| Non-dispersive infrared (NDIR) | How it worksGas molecules absorb infrared light at characteristic wavelengths; the absorption gives the concentration. | Suited forCO, CO₂, CH₄, SO₂, NO and hydrocarbons in emissions and process monitoring. | ConsiderationsWater vapour and cross-sensitive gases interfere — sample conditioning removes moisture and particulates. |
| Thermal conductivity | How it worksThe sample's thermal conductivity, compared with a reference, depends on its composition. | Suited forHydrogen, helium and binary mixtures — for example hydrogen purity in generator cooling gas. | ConsiderationsNon-specific: it works when the background composition is known and stable. |
| Gas chromatography | How it worksComponents separate in a column and are detected one after another. | Suited forMulti-component composition — natural gas and calorific value, hydrocarbon streams. | ConsiderationsCycle times of minutes, carrier gases and specialist maintenance; usually housed in a shelter. |
| Tunable diode laser (TDLAS) | How it worksA laser scanned across one absorption line measures a single component very selectively. | Suited forFast measurement of O₂, H₂O, NH₃, HCl or CO in harsh process and stack conditions, often across the duct. | ConsiderationsOptical alignment and dust load on the path matter; typically one or few components per analyzer. |
General engineering guidance. Limits and performance depend on the specific instrument and variant — confirm them against the manufacturer's datasheet for the selected model.
03Specify
What to specify
The parameters that decide the selection. State each with its unit; where a value is not known yet, say so — it becomes part of the engineering review.
Components and ranges
Each component and its range (ppm or %) decides the principle and whether one analyzer can cover several.
Background composition
Cross-sensitive gases, moisture and particulates bias many principles and shape the conditioning.
Process conditions
Temperature, pressure, dust, moisture and corrosives at the sample point decide in-situ versus extractive.
Sample conditioning
Keep the sample above its dew point or remove moisture in a controlled way — soluble gases such as SO₂ and NO₂ are lost in condensate.
Response time
Control loops need short lag; line length, flow and volume set the delay as much as the analyzer.
Accuracy and regulation
Emission monitoring follows regulatory requirements for certification, validation and data handling.
Calibration and validation
Calibration gases, automatic zero and span, and where the cylinders will be located.
Output and communication
4–20 mA per component, Modbus or Ethernet for many values and diagnostics, relays for alarms and status.
Area classification
Analyzers near process units may need certified or purged enclosures, or a shelter in a safe area.
Utilities and access
Instrument air, power, carrier or calibration gases, drains — and space to maintain the system.
04Integrate
Outputs & communication
Interfaces typically offered in this category, and what each means for the control system. Availability depends on the specific model.
- 4–20 mAAnalog
- Current loop with a live zero: 4 mA is the bottom of the range, so a broken wire (0 mA) is distinguishable from a zero reading. Two-wire (loop-powered) on most transmitters; four-wire with an active output on line-powered instruments such as analyzers — the I/O channel must match. Accepted by practically every PLC and DCS analog input.
- HARTDigital over analog
- A digital signal (Bell 202 FSK, 1200/2200 Hz) superimposed on the 4–20 mA loop — configuration, diagnostics and secondary variables over the existing two wires.
- Modbus RTUSerial
- Serial client/server (formerly master/slave) protocol, typically over RS-485: several devices share one multi-drop cable and the client polls each for its values — common on analyzers, multivariable meters and packaged equipment.
- Industrial EthernetNetwork
- PROFINET, EtherNet/IP or Modbus TCP — the networks that connect controllers, remote I/O, drives and HMIs, and increasingly carry device data from the field as well.
- Relay / discreteDiscrete
- Switched contact or transistor output for alarms, interlocks and pump or valve control — it carries a state, not a value.
05Install
Installation practice
- Locate the probe where the gas is representative — away from stratification, air in-leakage and dead zones.
- Minimize lag with short sample lines, a fast loop or bypass, and pumps sized for the required response.
- Heat-trace lines and condition the sample wherever condensation would remove soluble components or damage the analyzer.
- Plan calibration-gas connections, validation routines and a maintainable location — often an analyzer panel or shelter.
06Products
Gas Analysis products
Status · no models listed
Specific models are not listed on the site.
Our engineers can recommend instruments against your process data. The selection checklist on this page is the information that decides it — send what you have.
How a review runs
AT01Share the process data
Medium, range, conditions, connection and the system it reports to.
02Engineering review
The measuring principle and the installation are checked against the application.
03Instrument options
Suitable devices are proposed with the data needed to confirm the selection.
Next steps
Where to go next
- 01SolutionAnalytical SystemsProcess and online analyzers with sampling, sample conditioning, analyzer panels and control-system integration.
- 02Resource4–20 mA and HART: How Analog Instrument Signals WorkLive zero, loop power, loop resistance and the digital layer HART adds.
- 03Related categoryHumidity & Dew PointRelative humidity and dew-point measurement for air and process gases.
Engineering enquiry
Planning an online gas analysis system?
Share the component to measure, the expected range, the sample conditions and the system it reports to. Our engineers can help match the analyzer principle and the sampling system to the application.