Sensors 2012, 12(5), 6746-6763; doi:10.3390/s120506746
Article

A Compact Optical Instrument with Artificial Neural Network for pH Determination

Sonia Capel-Cuevas 1 email, Nuria López-Ruiz 2 email, Antonio Martinez-Olmos 2 email, Manuel P. Cuéllar 3 email, Maria del Carmen Pegalajar 3 email, Alberto José Palma 2 email, Ignacio de Orbe-Payá 1 email and Luis Fermin Capitán-Vallvey 1,* email
1 Department of Analytical Chemistry, Campus Fuentenueva, Faculty of Sciences, University of Granada, E-18071 Granada, Spain 2 Department of Electronics and Computer Technology, Campus Fuentenueva, Faculty of Sciences, University of Granada, E-18071 Granada, Spain 3 Department of Computer Science and Artificial Intelligence, E.T.S. Ingenierías Informática y de Telecomunicación, University of Granada, E-18071 Granada, Spain
* Author to whom correspondence should be addressed.
Received: 15 April 2012; in revised form: 15 May 2012 / Accepted: 21 May 2012 / Published: 22 May 2012
(This article belongs to the Section Chemical Sensors)
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Abstract: The aim of this work was the determination of pH with a sensor array-based optical portable instrument. This sensor array consists of eleven membranes with selective colour changes at different pH intervals. The method for the pH calculation is based on the implementation of artificial neural networks that use the responses of the membranes to generate a final pH value. A multi-objective algorithm was used to select the minimum number of sensing elements required to achieve an accurate pH determination from the neural network, and also to minimise the network size. This helps to minimise instrument and array development costs and save on microprocessor energy consumption. A set of artificial neural networks that fulfils these requirements is proposed using different combinations of the membranes in the sensor array, and is evaluated in terms of accuracy and reliability. In the end, the network including the response of the eleven membranes in the sensor was selected for validation in the instrument prototype because of its high accuracy. The performance of the instrument was evaluated by measuring the pH of a large set of real samples, showing that high precision can be obtained in the full range.
Keywords: portable instrument; H coordinate; HSV colour space; pH sensor array; neural networks

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Cite This Article

MDPI and ACS Style

Capel-Cuevas, S.; López-Ruiz, N.; Martinez-Olmos, A.; Cuéllar, M.P.; del Carmen Pegalajar, M.; Palma, A.J.; de Orbe-Payá, I.; Capitán-Vallvey, L.F. A Compact Optical Instrument with Artificial Neural Network for pH Determination. Sensors 2012, 12, 6746-6763.

AMA Style

Capel-Cuevas S, López-Ruiz N, Martinez-Olmos A, Cuéllar MP, del Carmen Pegalajar M, Palma AJ, de Orbe-Payá I, Capitán-Vallvey LF. A Compact Optical Instrument with Artificial Neural Network for pH Determination. Sensors. 2012; 12(5):6746-6763.

Chicago/Turabian Style

Capel-Cuevas, Sonia; López-Ruiz, Nuria; Martinez-Olmos, Antonio; Cuéllar, Manuel P.; del Carmen Pegalajar, Maria; Palma, Alberto José; de Orbe-Payá, Ignacio; Capitán-Vallvey, Luis Fermin. 2012. "A Compact Optical Instrument with Artificial Neural Network for pH Determination." Sensors 12, no. 5: 6746-6763.

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