Cited by 12Water Quality Monitoring and AnalysisScientific Measurement and Uncertainty EvaluationFault Detection and Control Systems

To calibrate or not to calibrate, that is the question

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Samuelsson, Oscar, Lindblom, Erik U., Björk, Anders, Carlsson, Bengt·2023·Water Research

Abstract

Sensors used for control have become widespread in water resources recovery facilities during the strive for resource efficient operations. However, their accuracy is reliant on uncertain laboratory measurements, which are used for calibration and, in turn, to correct for sensor drift. At the same time, current sensor calibration practices are lacking clear theoretical understanding of how measurement uncertainties impact the final control action. The effects of a customarily, and ad hoc, applied calibration threshold are unknown, leading to the current situation where many wastewater treatment processes are controlled by measurements with unknown accuracy. To study how sensor accuracy is affected by calibration, including varying calibration thresholds, we developed a simple theoretical model with closed-form expressions based on the variance and bias in sensor and laboratory measurements. The model was then simulated to yield the results, which showed no practical gain of using a calibration threshold, apart from the situation when calibration is more time-consuming than validation. By contrast, the best accuracy was obtained when consistently executing calibration, which opposes common practice. Further, the sensor calibration error was shown to be transferred to the process, causing a similar deviation from the setpoint when the same sensor was used for control. This emphasizes the importance of minimizing laboratory measurement uncertainties during calibration, which otherwise directly impact operations. Due to these findings we strongly advice shifting mindset from considering calibration as a sequential detection and correction approach, towards an estimation approach, aiming to estimate bias magnitude and drift speed.

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  1. Eurachem, 2019. Eurachem/EUROLAB/CITAC/Nordtest/AMC Guide: Measurement Uncertainty Arising from Sampling: a Guide to Methods and Approaches, 2nd ed. Eurachem. http://refhub.elsevier.com/S0043-1354(2201283-0/sbref0003)
  2. International Organization for Standardization, 1994. Accuracy (Trueness and Precision) of Measurement Methods and Results -Part 1: General Principles and definiTions (ISO 5725-1:1994). International Organization for Standardization. http://refhub.elsevier.com/S0043-1354(2201283-0/sbref0007)
  3. Kay, S.M., 1998. Fundamentals of Statistical Signal Processing: Detection Theory. Prentice-Hall PTR, Upper Saddle River, NJ, USA. http://refhub.elsevier.com/S0043-1354(2201283-0/sbref0008)
  4. S. Andersson, L.Å., Samuelsson, O., Nilsson, S., 2019. Instrumentera R ¨ att på Avloppsreningsverk. IVL Swedish environmental research institute, Svenskt Vatten. http://refhub.elsevier.com/S0043-1354(2201283-0/sbref0014)

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Authors
Samuelsson, O., Lindblom, E. U., Björk, A., & Carlsson, B.
Affiliations
  • Uppsala University (SE)
  • Lund University (SE)
  • IVL Swedish Environmental Research Institute (CN)
Corresponding author
Samuelsson, Oscar
Venue
Water Research
Publisher
Elsevier BV
Published
2023-02
Volume
229
Pages
119338
ISSN
0043-1354 (ISSN-L)
OpenAlex
W4308886926
Cited by
12
References
12
Citations by year
2025: 7 · 2024: 3 · 2023: 2
FWCI
1.69
Type
journal article
Language
en
Open access
Locations
  • Water Research (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Uppsala University Publications (Uppsala University) (submittedVersion, other-oa)
  • Lund University Publications (Lund University) (submittedVersion)
Funders
Svenskt Vatten
Topics
  • Physical Sciences › Environmental Science › Waste Management and Disposal › Water Quality Monitoring and Analysis
  • Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Scientific Measurement and Uncertainty Evaluation
  • Physical Sciences › Engineering › Control and Systems Engineering › Fault Detection and Control Systems
Keywords
sensor calibration, sensor drift, measurement uncertainty, wastewater treatment process control, sensor bias estimation, closed-form model, control accuracy
MeSH terms
Calibration, Models, Theoretical, Bias

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