Battery-Less NFC Sensor for pH Monitoring

Abstract

In this paper, we present a low-cost battery-less color sensor based on Near Field Communication (NFC). This system consists of a color sensor connected to a low-power microcontroller connected to an NFC chip. The energy needed to power up the chipset is retrieved from the magnetic field generated by the reader, i.e., a commercial smartphone. The low cost of NFC chips affords the opportunity to manufacture low-cost tags with sensing capability. We have developed a mobile application to simultaneously present the data and send them to a database in the cloud. The system has been tested with several pH reactive strips. The pH was determined via color measurement using the HSV color space. A simple linear relationship was found between the Hue parameter and the pH. Comparison with the pH determination via smartphone camera showed that the accuracy was greater when the NFC colorimeter was used.