A New Pulse Delta-Sigma CO2 NDIR Gas Detector

Steven Z Y Shen,Hilbert C S Shen,Chi-Feng Chen

doi:10.4236/opj.2016.68b037

Abstract

This work describes the implementation and the modeling of an infrared gas sensor with pulse delta-sigma sensing architecture. Beyond the conventional technique of constant periodic heating of infrared light source, our proposed delta-sigma architecture with closed-loop feedback system is built with the hybrid combination of a CO2 infrared sensor with a specific wavelength filter, an infrared MEMS heater, a chopper amplifier, threshold comparator, ARM based MPU and discrete electronic devices. After a modeling of system, we built a model for the description of relationship between gas concentration and sensor by the duty of heating. The measurement results show a good linear behavior of signal and it proves to be a practical for all the NDIR measuring techniques and this work also gives a new approach not only to measure gas concentration fast but also obtain the high resolution.

Highlights

IntroductionTechnology changes for the better day by day, and month by month
Nowadays, technology changes for the better day by day, and month by month
The feedback loop is built based on the received intensity of infrared sensor during the heating cycle

Summary

Introduction

Technology changes for the better day by day, and month by month. It makes our quality of life better and better. First type is using NDIR (non-dispersive infrared sensor) [1] method, and second is using chemical method. The NDIR method is a physical method, which have high sensitivity, long-term stability and do not pollute environment. In order to solve this problem, we combine delta-sigma architecture [3] [4] with NDIR-based system and using a feedback loop to surmount the problem of offset which is infrared radiation intensity. We modulate gain and reference voltage of comparator for changing sensitivity of the measuring instrument. (2016) A New Pulse Delta-Sigma CO2 NDIR Gas Detector.

Beer-Lambert’s Law Using in NDIR Technique

Proposed Delta-Sigma Architecture for NDIR Sensing

Theory

Results and Experiment

Conclusion