A parallel readout circuit for a space-based non-dispersive infrared gas analyzer

Abstract

More sophisticated non-dispersive infrared (NDIR) sensors for gas analysis have been developed in recent years, with many references in the literature. This technique is one of the most cost-effective methods to quantify the concentration of a target gas by measuring its absorption of infrared radiation. Dual channel thermopiles comprised of target and reference filter channels are reliably used to monitor the target gas for NDIR sensors. In recent years, commercial off-the-shelf quad-channel thermopiles with integrated passband infrared absorption filters have become available and enable up to three gas mixture detection and quantification, but there is no truly parallel readout circuit available for signal post processing. These sensors with their high sensitivity, fast response time and no cooling requirement makes them ideal candidates for applications that require monitoring multiple gases in real time. Usually, an NDIR sensor uses a cost-effective micro-controller for signal post processing, this limits the monitoring of multiple gases to a serial readout architecture. In this paper, we present a proof-of-concept non-dispersive infrared-red (NDIR) gas analyzer that has been realized with a quad-channel thermopile and a parallel readout circuitry consisting of a multi-channel digitizer (MCD) application specific integrated circuit (ASIC) and a field programmable gate array (FPGA). The parallel readout architecture will help considerably in the calibration schema. The NDIR gas analyzer will be used in a future space-based instrument application to ensure the safe transfer of sublimated volatiles from a comet sample containment system to a gas containment system within the operational pressure-temperature condition.