Gas Analyzers for Process and Emission

A gas analyser determines which gases a gas mixture contains and at what concentration. Unlike a gas warning device, which only raises an alarm when a limit is exceeded, a gas analyser delivers continuous quantitative readings – in percent by volume, ppm or mg/m³. It is a measuring instrument, not a safety detector.

In industrial use the device sits at the end of a measuring chain: a probe extracts the sample gas, sample gas conditioning dries and filters it, and only then does it reach the analyser. Which measurement principle works there depends on the gas – NDIR for infrared-active components such as CO, CO₂, CH₄ or SO₂, paramagnetic measurement and zirconium oxide sensors for oxygen, TDLAS as a laser method for methane, thermal conductivity detection for binary mixtures and electrochemical cells for components such as H₂S.

Fresenius Instruments offers one of the most comprehensive ranges of gas analyzers on the European market. At its core is the GA220 – our multi-gas flagship that analyzes up to 8 sample gas inlets, combining NDIR, paramagnetic, electrochemical and ZrO₂ sensors in a compact 19-inch rack housing. For single-gas measurements, the GA210 variants are available: the GA210 O₂ with paramagnetic or zirconium oxide sensor delivers highly precise oxygen readings for combustion control and emission monitoring.

Our portfolio also includes the GA150 as a solvent specialist with heated cuvette, the GA100 Portable for battery-powered mobile measurements on site, and the TINA InSitu analyzer that measures directly in the process stream – without gas conditioning, with response times under 10 seconds, tested to DIN EN 60079-29-1. For gases that do not absorb in the infrared – such as hydrogen, helium or ammonia – the FTC300 uses the thermal conductivity principle (TCD).

All Fresenius Instruments gas analyzers are developed and manufactured in Germany. Premium components from German suppliers ensure a device lifespan of over 30 years with 10+ years spare parts guarantee. The patented automatic zero-point correction without test gas saves you ongoing operating costs and significantly reduces maintenance effort – a decisive advantage over modular systems from other manufacturers.

With over 175 years of experience in analytical measurement technology, worldwide on-site service and the Cloud Connect Kit for real-time remote monitoring of your installations, Fresenius Instruments offers not just gas analyzers but a holistic measurement solution for emission monitoring, biogas plants, process control and environmental measurement technology.

The measurement principles in detail

NDIR – non-dispersive infrared measurement. By far the most widely used method in process and emission measurement. Infrared-active gases absorb light at a wavelength characteristic of them; the attenuation of the beam gives the concentration. This covers CO, CO₂, CH₄, SO₂, NO and many hydrocarbons. NDIR is robust, stable over the long term and low on calibration – in our analysers additionally through a patented zero-point correction without test gas.

Paramagnetic oxygen measurement. Oxygen is attracted in a magnetic field, almost all other process gases are not – which makes the method highly selective for O₂ and free of consumables. Our measuring cell works without moving parts and is therefore insensitive to vibration, qualifying it for installation close to the plant.

Zirconium oxide sensors (ZrO₂). The second design for oxygen, made for hot gases. A heated ceramic cell generates a voltage between sample gas and reference air that depends on the oxygen content. Typical for combustion control and firing optimisation, where measurement happens directly in the hot flue gas.

TDLAS – tunable diode laser spectroscopy. A laser is tuned precisely to a single absorption line of the target gas. Because that line is so narrow, accompanying gases barely interfere – the method is highly selective and fast. We use TDLAS for methane, for instance in biomethane feed-in monitoring.

Thermal conductivity detection (TCD). Gases conduct heat differently. In a binary mixture whose two components are known, the mixing ratio follows directly – hydrogen in nitrogen, for example. A simple, very robust principle without optical components.

Electrochemical sensors. The target gas reacts at an electrode and generates a current proportional to concentration. Useful where optical methods reach their limits, for instance with H₂S. Electrochemical cells are wear parts and are replaced at fixed intervals – that belongs in the cost calculation.

No single method covers everything. That is why the GA220 combines several principles in one 19" housing and takes up to eight sample gas inlets, while the GA210 is a single-gas analyser designed for one component. We do not offer gas chromatography or FTIR – where those methods are required, we will tell you so openly.