Reg Doubt in LMP91051 gas/Chemical sensor

Dear All,

One of my customer is in initial testing phase of the NDIR gas bench with Thermopile sensor ST120Quad with your LMP91051

Analog front end IC in the output of Thermopile sensor for signal conditioning.


They observed that the amplitude of sensor (at the output of AFE) is less. Please find attached the signals captured during passing

Fresh air and when passing a Gas mixture( CO= 3.57%, CO2=14.50% and Propane = 2090ppm). Channel 1 is CO and HC, Channel 2 is CO2 and Ref.

Gain set in channel 1 is = 4000 and Channel 2  = 8000   .

The channel switching time set is 5ms.  IR LED ON/OFF time is 250ms( 250 ms ON and 250ms OFF).


Please let us know whether this is ok? waveforms are attached for reference. please advise.


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