Evaluation of low-cost formaldehyde sensors calibration

Low-cost sensors (LCS) are becoming ubiquitous in the market; however, calibration is needed before reliable use. An evaluation of eight identical pre-calibrated formaldehyde LCS presented here. The and a reference instrument were exposed to pollutant source(s) for measurements. After one year, some tests repeated check drift stability calibration. This paper presents methodologies using data with significant autocorrelations. Autocorrelation sensor measurements might be present when performing frequent sampling. To obtain results, must consider autocorrelation or serial correlation between subsequent Experimental design can used reduce risk highly autocorrelated measurement. Ordinary Least Squares Estimations should not autocorrelated, as their central assumption that residuals independent identically distributed. Two alternative methods considering first-order Markov scaling proposed: Maximum Likelihood Restricted Estimation (REML). REML has better compensations estimated parameters parameters. Akaike information criterion was select most resulting temperature. results only sensors. According EPA's recommendations, tested LCSs Tier III, supplementary monitoring. over-and under-estimated values obtained by sensor, but they very similar dynamic responses, indicating could detect concentration changes after