Gas Filter Correlation - GFC sensors deliver stable, ultra-accurate gas analysis

An advanced form of Infrared sensing, Gas Filter Correlation (GFC) technology is ideal in applications with interferent background gases, delivering precise, sensitive measurements. It is used in our SERVOTOUGH SpectraExact 2500 photometric analyzer, and is a key technology for our SERVOPRO multi-gas analyzers, the MultiExact 4100, MultiExact 4200, and 4900 Multigas.

GFC sensing is an enhanced version of the photometric analysis used in our Infrared technologies.

It performs effectively where extremely accurate, low-level measurements are needed, or where background gases may interfere with the measurement.

Gases have the ability to absorb unique light wavelengths – GFC sensing uses that property to detect the concentration of a selected gas in a mixture. Two gas-filled cuvettes are mounted on a rotating disk, each passing through a beam of light alternately.

One cuvette (the measure cuvette) is typically filled with nitrogen while the other cuvette (the reference cuvette) is filled with a sample of the gas to be measured. Light is passed through the gas to be measured: the difference in absorbance is measured and provides a direct output of the gas concentration.

Offering real-time measurement response, GFC measurements are unaffected by background gases, and the technique is virtually immune to obscuration of the optics. This prevents sensor drift, reducing calibration frequency.

Related and alternative technologies

GFC sensing also works alongside single-beam, single-wave Infrared sensing to provide real-time process analysis for a range of industrial applications. Only gases with infrared lines can be measured by GFC technology, so it is not suitable for noble gases, or single element diatomic molecules such as N2 or O2.

Key applications

Continuous emissions monitoring

Ethylene, chlorine and TDI production processes

HyCO process control

Key benefits

Low cross interference by background gases

Immune to obscuration of the optics

Low sensor drift, reducing calibration frequency

Ideal for

Providing a lower-cost alternative to more complex technologies when dealing with applications that require the measurement of low-level gases with high levels of interfering background gases.

Explore the GFC analyzers we have for your process

Learn more about all our gas analyzer solutions that use this sensor technology.

Search Servomex Gas Filter Correlation analyzers

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4900 Multigas


The 4900 Multigas is a high-performance CEMS analyzer designed for a wide range of multi-gas measurements.

  • Advanced digital multi-gas CEMS analysis
  • Up to four simultaneous gas stream measurements
  • Ultra-stable, accurate, non-depleting sensors
  • Auto-calibration for reduced operational needs
  • Intuitive-use icon-driven colour touchscreen
  • Digital communications for remote access

MultiExact 4100


A high-performance multi-gas analyzer designed to provide up to four simultaneous gas stream measurements.

SERVOPRO MultiExact 4100
  • Highly adaptable multi-gas analyzer
  • Provides up to four simultaneous measurements
  • Wide range of sensing technology options
  • Versatile solution for industrial and medical gases
  • Built-in support for moisture sensor
  • Optional advanced digital protocols

MultiExact 4200


The MultiExact 4200 analyzes up to four gases simultaneously for Syngas and HyCO

  • For HyCO, Syngas, H2, and gas transfer applications
  • A high-specification multi-gas analyser
  • Measures up to four gas streams simultaneously
  • Combines industry-leading sensing technologies
  • Low cost of ownership and minimal maintenance
  • Intuitive-use icon-driven colour touchscreen

SpectraExact 2500

SERVOTOUGH Hazardous Area

Flexible single and multicomponent gas analysis capability for corrosive, toxic and flammable sample streams.

  • Rugged, reliable photometric analysis
  • Designed for continually flammable samples
  • Suitable for hazardous area applications
  • Ideal for diverse gas sample types
  • Uses field-proven non-depleting technologies
  • Certified for gases

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Need more advice? Contact the gas analysis experts today

If you still need guidance to find the best solution for your process, we’re here to help. Our expert team combines applications knowledge with extensive experience and deep understanding of the sensing technologies available. We’ll help you find the solution that meets your unique needs.

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