Transmitter IR29

(NDIR) IR technology with increased safety "e"

Measuring method

IR transmitters have become recognised as reliable gas warning systems for explosion protection.

They are used to detect individual combustible gases or a wide range of gases. This involves sending an IR beam with a certain light intensity through a measuring space and then capturing it with a detector. Parts of this beam are absorbed by, amongst other things, hydrocarbon molecules. The reduced light intensity of the beam is registered by beam detectors and converted into a signal as the existing gas concentration % LEL.


A special feature of our IR technology is the measurement of combustible gases even above the lower explosion limit. Oxygen is not required for the measurement. With this technology there is basically no risk of contaminating the sensor, e.g. through silicone vapours or hydrogen sulphide when using catalytic combustion sensors.


IR transmitters with two wavelengths are typically used. One so-called reference wavelength and just one measuring wavelength. Very strict limits are applied to these systems. The absorption spectra of many hydrocarbons are located in the wavelength range of 3.3 µm and overlap to a large extent. This means that gases with overlapping spectra and just one measuring wavelength can no longer be clearly distinguished. Some hydrocarbons, e.g. the frequently used welding gas acetylene, are non-absorbing in the wavelength range of 3.3 µm, but absorb instead in neighbouring wavelength ranges.

In many practical applications, it is not essentially important which gas is responsible for the explosion risk. Therefore, early warnings through the broadband measurement of hydrocarbons in order to monitor the lower explosion limit (LEL) must be guaranteed. False alarms with uncritical concentrations of individual gases or solvents are thus absolutely unacceptable.

These requirements are unresolvable problems for systems with just two wavelengths.

Patented GfG technology

The worldwide patented technology of the IR29 has been developed to solve the aforementioned problems. The gold-plated mirror optics of the sensor contains two radiators and up to four detector elements with different optical filters. The precisely calculated, microstructured and pure gold coated mirror optics of the IR29 are supplied for the first time without beam splitters. This helps to cut signal losses by 50% and to completely avoid the physically-related disadvantages of a beam splitter. The measured values from two additional wavelengths (four wavelengths in total) ensure improved detection of individual gases and thus enhanced selectivity. The result in the prevention of false alarms. Only a 4-wavelength system always guarantees early warnings and the simultaneous prevention of false alarms.


The worldwide first and only intrinsically safe IR gas transmitter with patented 4-beam 4-wavelength technology is now also available as a version with increased safety for explosion protection. The ignition protection class "intrinsically safe", which is so essential for industrial plants, allows for the easy replacement of existing gas transmitters and the application of an already available three-core cable.

Universal application

The IR29 with its robust V4A stainless steel housing and stainless steel impact protection at the transmitter foot has been designed to withstand the harshest environmental conditions. The application areas of the dust and water-protected structure range from production and storage areas to disposal sites, biogas plants, wastewater treatment plants, mines and oil rigs.

Internal data logger

A standard built-in data logger records all measuring data, such as minimum/maximum values, average values and alarm events, of the last 24 hours in a ring buffer. The recording can also be shown on the display as a 2 hour and 8 hour trend indicator. The histogram mode can be selected as a permanent display of the measured values. These values are continuously updated.

Graphical display

Measured values are shown on the high-contrast graphical display. The display can be rotated 180° depending on the installation of the IR29.

Self diagnosis

Processor-based signal processing enables the systematic compensation of temperature dependencies, ageing influences and soiling effects. Safety-relevant functions are monitored permanently via self-diagnosis procedures and a possibly required service is indicated automatically. Daily interfering factors, such as insects or dust and dirt accumulation, are almost completely eliminated by the innovative design.

Pressure, moisture and temperature compensation

The measuring accuracy of IR sensors depends on partial pressure and thus also air pressure. Climatic fluctuations or barometric high pressure therefore influence the measuring result. Furthermore, the absorption spectrum of water almost completely covers that of hydrocarbon absorption in the 2.7 to 3.3 µm range. Air humidity therefore initially generates a measuring signal the same as the actual measuring gas. This cross-sensitivity is of particular importance in warm areas with high relative humidity. An increase in the absolute water absorption capacity of air is not linear with the temperature, i.e. three times as much water can be absorbed at 40°C than at 20°C. This influence can only be compensated if the current moisture content of the air is known. The IR29 can be optionally equipped with a pressure and moisture sensor for compensation.

Maximum safety

The innovative display enables the realisation of completely safe warning concepts. Local displays and signals directly at the device can be used to provide an early warning of potential risks. This allows immediate on-site action before really hazardous situations occur.

Dust protection

A gas permeable, water-repellent diaphragm protects the absorption space of the transmitter against dust. The additional impact protection made from robust V4A stainless steel prevents mechanical damage to the optical components. The diaphragm can be cleaned or replaced in a matter of minutes.

Remote controls

The transmitter IR29 does not feature control elements for setting or servicing tasks. This helps to prevent accidental or unauthorised manipulation.

Service work at the transmitter IR29 is carried out using the remote control RC2.

The advantages at a glance

  • IR transmitter for explosion protection with increased safety
  • Patented IR technology (NDIR)
  • 4-beam, 4-wavelength technology
  • Temperature, moisture and pressure compensation
  • Maintenance and service-friendly
  • Ignition protection class with increased safety "e"

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GfG Gas Detection UK Ltd.

Unit 8, Griggs Business Centre
West Street, Coggeshall Essex, UK CO6 1NT