A New Smoke Concentration Measurement System: Low-Cost, High-Accuracy, and Easy-Implementation

This paper presents a new smoke concentration measurement system, which is designed based on the theory of light extinction. To implement the technique we developed, the hardware system, including a reflecting light path, balanced circuit design, and reasonable data acquisition and processing system, is constructed. In particular, a set of photodiode and preamplifier is specially applied and adjusted to monitor the incident and emergent light intensity simultaneously and to amplify the differential signal of light intensity while rejecting common-mode noise signals caused by light source and change of temperature, which, results in a maximum control of the driving and amplifying circuits´ linearity, stability, bandwidth, noise level and temperature drift through thorough insight into the circuit´s response models and careful testing. The system achieves satisfying performance, including: under room temperature, with the sensitivity of 0.12%/m (confidence level: 99.7%) and absolute accuracy of 0.12%/m (confidence level: 99.7%), also with errors no more than 6%/m (under 85°C) and 1%/m (under 45°C). Compared with previous measurement system, the meter we presented is more of benefit for the reason of lower cost, less complexity, and easier hardware implementation.