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Static water levels and geochemical field parameters
Published in Neal Wilson, Soil Water and Ground Water Sampling, 2020
A pH meter is generally accurate to ±0.1 pH unit. The pH meter must be manually or automatically compensated to correct for the effect of temperature on the instrument. This compensation does not, however, adjust the pH to a common temperature, so the temperature of the sample should be reported for each pH measurement.5 Analog meters (pH, specific conductance, dissolved oxygen) may need to be calibrated in the same position (e.g., lying flat or set upright) as when used, but this is not required for meters with digital displays.
Battery-Free Wireless Sensors for Healthcare and Food Quality Monitoring
Published in George K. Knopf, Amarjeet S. Bassi, Smart Biosensor Technology, 2018
Bradley D. Nelson, Salil Sidharthan Karipott, Samerender Nagam Hanumantharao, Smitha Rao, Keat Ghee Ong
Food spoilage can also change the pH in food. As a result, pH has been used in the food industry during both production and storage to ensure food quality and safety. The change in food pH can be attributed to the metabolic activity of bacteria or microbes when converting food (Brocklehurst & Lund 1988; Nychas et al. 2008). Conventionally, pH is measured as the electrical potential difference between two electrodes (sensing electrode and reference electrode) using a pH meter. Although accurate, a pH meter is not convenient due to the need for a pH probe and direct wire connection to a reader. Various wireless versions of the pH sensor were developed by combining pH electrodes with wireless sensor platforms. For example, the pH sensor developed by Horton et al. (2011) used a varactor to convert the electrode potential difference into a change in capacitance, which was connected to an inductor for form an LC sensor. A similar sensor was developed by Bhadra et al., demonstrating the application of an LC sensor in detecting fish (Bhadra et al. 2015; Huang et al. 2012) and milk (Bhadra et al. 2012, 2013) spoilage. The pH sensor reported by Huang et al. incorporated a different design by integrating the sensors with a radio frequency transponder (Huang et al. 2012).
Laboratory Equipment and Supplies in the Environmental Microbiology Laboratory
Published in Maria Csuros, Csaba Csuros, Klara Ver, Microbiological Examination of Water and Wastewater, 2018
Maria Csuros, Csaba Csuros, Klara Ver
A pH meter functions by measuring the electric potential between two electrodes that are immersed into the solution of interest. The basic principle is to determine the activity of the hydrogen ions by potentiometric measurement using a glass and a reference electrode. The most popular, called a combination electrode, incorporates the glass and the reference electrode into a single probe. The glass electrode is sensitive to the hydrogen ions, and changes its electrical potential with the change of the hydrogen ion concentration. The reference electrode has a constant electric potential. The difference in potential between these electrodes, measured in millivolts (mV), is a linear function of the pH of the solution. The scale of pH meters is designed so that the voltage can be read directly in terms of pH.
Smart water management system for residential buildings in Saudi Arabia
Published in Journal of Applied Water Engineering and Research, 2022
Potential of Hydrogen (pH) is a numeric scale applied to indicate the basicity or acidity of an aqueous solution. pH measurement is important in water purification monitoring, which is performed using pH meters. The pH meter has a glass proton-sensitive electrode, which creates a potential corresponding to the pH of a solution with reference to a silver chloride or calomel electrode. The purpose of the reference electrode is to preserve a constant potential at any given temperature. The glass electrode, usually located at the tip of the pH probe, allows hydrogen ions in the solution being measured to diffuse into the outer layer of the glass, whereas larger ions remain in the solution. The hydrogen ions concentration difference between the outside and inside of the probe generates a very small current. Hence, this current is proportional to the concentration of hydrogen ions in the solution being measured with a potential, E, that can be written as where E0 is the standard electrode potential at hydrogen ion activity (aH+) = 1 mol/l, R is the gas constant, T is the temperature in Kelvin and F is the Faraday constant. Most pH sensors are designed to produce an output of 0 mV at 7.0 pH, with a slope, or sensitivity, of −59.16 mV/pH at 25 °C. The ideal pH level of drinking water varies between 6 and 8.5.