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Thermo Fisher Scientific

FID Analog Filter


  • A customer has several Focus GC with FID operating with Chromquest software.  
  • The customer operates one Focus GC in the mode of analog filter range 1 and one Focus GC at an analog filter range of 100 as the samples have high concentrations.
  • The baseline on two of the systems has drifted down and is now around 0.0 millivolts (mV).  
  • The customer is currently running with a ignition threshold of 0.0 mV and the FID remains ignited.  
  • I discussed this issue with another Technical Support Representative and they indicated this is a common issue when using Analog filters and to overcome the issue the ignition threshold is set to 0.0 mV . 
  • The customer is using Chromquest as the software, and this will also be an issue with Chromeleon and Xcalibur.


  • Trace Ultra
  • Trace 1300
  • Trace 1310
  • ChromQuest
  • Chromeleon
  • Xcalibur


  • The only solution is to run with threshold set to 0.0. 
  • User can confirm that GC is working by removing the analog filter and confirming the signal is around 2-7 mV.