A Four-Terminal Water-Quality-Monitoring Conductivity Sensor
TL;DR: The main advantages of the proposed conductivity sensor include a wide measurement range, an intrinsic capability to minimize errors caused by fouling and polarization effects, and an automatic compensation of conductivity measurements caused by temperature variations.
Abstract: In this paper, a new four-electrode sensor for water conductivity measurements is presented. In addition to the sensor itself, all signal conditioning is implemented together with signal processing of the sensor outputs to determine the water conductivity. The sensor is designed for conductivity measurements in the range from 50 mS/m up to 5 S/m through the correct placement of the four electrodes inside the tube where the water flows. The implemented prototype is capable of supplying the sensor with the necessary current at the measurement frequency, acquiring the sine signals across the voltage electrodes of the sensor and across a sampling impedance to determine the current. A temperature sensor is also included in the system to measure the water temperature and, thus, compensate the water-conductivity temperature dependence. The main advantages of the proposed conductivity sensor include a wide measurement range, an intrinsic capability to minimize errors caused by fouling and polarization effects, and an automatic compensation of conductivity measurements caused by temperature variations.
Citations
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31 Oct 2001
TL;DR: The American Society for Testing and Materials (ASTM) as mentioned in this paper is an independent organization devoted to the development of standards for testing and materials, and is a member of IEEE 802.11.
Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.
3,792 citations
TL;DR: In this paper, the authors provide a thorough review of the advances in sensor technology for measurement of common water quality parameters (pH, turbidity, free chlorine, dissolved oxygen, and conductivity) in drinking water distribution systems.
Abstract: Online drinking water quality monitoring technologies have made significant progress for source water surveillance and water treatment plant operation. The use of these technologies in the distribution system has not been favorable due to the high costs associated with installation, maintenance, and calibration of a large distributed array of monitoring sensors. This has led to a search for newer technologies that can be economically deployed on a large scale. This paper includes a brief description of important parameters for drinking water and current available technologies used in the field. The paper also provides a thorough review of the advances in sensor technology for measurement of common water quality parameters (pH, turbidity, free chlorine, dissolved oxygen, and conductivity) in drinking water distribution systems.
104 citations
Cites background or methods from "A Four-Terminal Water-Quality-Monit..."
...The conductivity sensing unit developed by Ramos et al. (2008) consists of a plastic tube, with two ring-shaped electrodes inside to force the electric field, two metallic tips to measure the output voltage (see Figure 19) and a temperature sensor....
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...Conductivity Inductive/electrode sensor Four-terminal electrode (Ramos et al., 2008) They offer low cost and accurate conductivity sensors....
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...Ramos et al. (2008) and Li et al. (2011) developed a four-terminal WQM conductivity (electrode) sensor....
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TL;DR: It is demonstrated that it is feasible to measure water conductivity using solenoid coils and that this is a low cost application for groundwater monitoring.
Abstract: The main aim of smart cities is to achieve the sustainable use of resources. In order to make the correct use of resources, an accurate monitoring and management is needed. In some places, like underground aquifers, access for monitoring can be difficult, therefore the use of sensors can be a good solution. Groundwater is very important as a water resource. Just in the USA, aquifers represent the water source for 50% of the population. However, aquifers are endangered due to the contamination. One of the most important parameters to monitor in groundwater is the salinity, as high salinity levels indicate groundwater salinization. In this paper, we present a specific sensor for monitoring groundwater salinization. The sensor is able to measure the electric conductivity of water, which is directly related to the water salinization. The sensor, which is composed of two copper coils, measures the magnetic field alterations due to the presence of electric charges in the water. Different salinities of the water generate different alterations. Our sensor has undergone several tests in order to obtain a conductivity sensor with enough accuracy. First, several prototypes are tested and are compared with the purpose of choosing the best combination of coils. After the best prototype was selected, it was calibrated using up to 30 different samples. Our conductivity sensor presents an operational range from 0.585 mS/cm to 73.8 mS/cm, which is wide enough to cover the typical range of water salinities. With this work, we have demonstrated that it is feasible to measure water conductivity using solenoid coils and that this is a low cost application for groundwater monitoring.
69 citations
TL;DR: In this paper, the authors presented micro-sensors fabricated and implemented in a serpentine channel interface for the measurement of pH and conductivity, two important water quality parameters.
Abstract: The development of cost-effective, durable and sensitive on-line water quality monitoring sensors that can be installed across water distribution networks has attracted attention to increase the frequency of monitoring and hence reduce the risk of accidental or deliberate contaminations or improve routine control of water quality. This paper presents microsensors fabricated and implemented in a serpentine channel interface for the measurement of pH and conductivity, two important water quality parameters. The performance of these sensors was tested in both still (static) and flowing (dynamic) water. The serpentine channel interface, numerically optimized, provides a constant flow and a constant outlet pressure condition for dynamic experiments. Tests conducted for evaluating the effect of the exposure time on the sensor performance show no change in the sensor response even after one month. Finally, the pH and conductivity sensors were compared against the common commercial sensors used for evaluating water quality. The results show that the pH and conductivity sensors are as precise as the commercial sensors in both static and dynamic conditions. However, the cost of the sensors presented here is significantly lower than that of the commercial sensors.
61 citations
TL;DR: Remotely-sensed and integrated data of salt-affected areas combined with in situ and lab-based observations have never been so easy and rapid to acquire, precise and applicable on huge scales, representing a valuable tool for policy-makers and other stakeholders in implementing targeted measures to control and prevent ecosystem degradation.
Abstract: A great portion of Earth's freshwater and land resources are salt-affected and thus have restricted use or may become unsuitable for most human activities. Some of the recent scenarios warn that environmental salinization processes will continue to be exacerbated due to global climate change. The most relevant implications and side-effects in ecosystems under excessive salinity are destructive and long lasting (e.g. soil dispersion, water/soil hypersalinity, desertification, ruined biodiversity), often with non-feasible on site remediation, especially at larger scales. Agro-ecosystems are very sensitive to salinization; after a certain threshold is reached, yields and food quality start to deteriorate sharply. Additionally, salinity often coincides with numerous other environmental constrains (drought, waterlogging, pollution, acidity, nutrient deficiency, etc.) that progressively aggravate the threat to food security and general ecosystem resilience. Some well-proven, widely-used and cost-effective traditional ameliorative strategies (e.g. conservation agriculture, application of natural conditioners) help against salinity and other constraints, especially in developing countries. Remotely-sensed and integrated data of salt-affected areas combined with in situ and lab-based observations have never been so easy and rapid to acquire, precise and applicable on huge scales, representing a valuable tool for policy-makers and other stakeholders in implementing targeted measures to control and prevent ecosystem degradation (top-to-bottom approach). Continued progress in biotechnology and ecoengineering offers some of the most advanced and effective solutions against salinity (e.g. nanomaterials, marker-assisted breeding, genome editing, plant-microbial associations), albeit many knowledge gaps and ethical frontiers remain to be overcome before a successful transfer of these potential solutions to the industrial-scale food production can be effective.
61 citations
References
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31 Oct 2001
TL;DR: The American Society for Testing and Materials (ASTM) as mentioned in this paper is an independent organization devoted to the development of standards for testing and materials, and is a member of IEEE 802.11.
Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.
3,792 citations
Book•
29 Dec 1998
TL;DR: In this paper, the authors present a characterization of measurement characteristics, including time and frequency measurements, as well as the properties of different types of measurements, such as thermal, chemical, and signal processing.
Abstract: Measurement Characteristics. Spatial Variables Measurement. Time and Frequency Measurement. Mechanical Variables Measurement Solid. Mechanical Variables Measurement Fluid. Mechanical Variables Measurement Thermal. Electromagnetic Variables Measurement. Optical Variables Measurement. Radiation Measurement. Chemical Variables Measurement. Biomedical Variables Measurement. Signal Processing. Displays. Control. Appendices. Index.
1,010 citations
"A Four-Terminal Water-Quality-Monit..." refers background in this paper
...The proportionality coefficient (KC) depends on the geometry of the sensor that must be designed according to the target conductivity range [6], [7]....
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TL;DR: In this article, the dielectric constant of saline water was represented by an equation of the Debye form and the parameters for the parameters were given as functions of the water temperature and salinity.
Abstract: The dielectric constant of saline water may be represented by an equation of the Debye form. Equations for the parameters in the Debye expression are given as functions of the water temperature and salinity.
715 citations
TL;DR: In this paper, the authors present fluxgate sensors with a resolution comparable with high-temperature superconducting quantum interference devices (SQUIDs), while their precision is the best of vectorial field sensors.
Abstract: This paper reviews recent achievements in the technology and design of fluxgate sensors and magnetometers. The major recent trends were decreasing of the sensor size, power consumption and price, and, on the other hand, increasing of the precision in the large range of the measured fields. The potential frequency range was increased up to units of kHz. Present fluxgate sensors have a resolution comparable with high-temperature superconducting quantum interference devices (SQUIDs), while their precision is the best of vectorial field sensors.
302 citations
"A Four-Terminal Water-Quality-Monit..." refers background in this paper
...There are two main types of conductivity sensors: electrode (or contacting sensors) and toroidal or inductive sensors [3]–[5]....
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TL;DR: The field profiles obtained by scanning a biological tissue show the potential of this methodology for clinical applications, and images obtained from isolated conducting tubes show that it is possible to distinguish two tubes separated 17 mm from each other.
Abstract: A data-acquisition system has been developed to image electrical conductivity of biological tissues via contactless measurements. This system uses magnetic excitation to induce currents inside the body and measures the resulting magnetic fields. The data-acquisition system is constructed using a PC-controlled lock-in amplifier instrument. A magnetically coupled differential coil is used to scan conducting phantoms by a computer controlled scanning system. A 10000-turn differential coil system with circular receiver coils of radii 15 mm is used as a magnetic sensor. The transmitter coil is a 100-turn circular coil of radius 15 mm and is driven by a sinusoidal current of 200 mA (peak). The linearity of the system is 7.2% full scale. The sensitivity of the system to conducting tubes when the sensor-body distance is 0.3 cm is 21.47 mV/(S/m). It is observed that it is possible to detect a conducting tube of average conductivity (0.2 S/m) when the body is 6 cm from the sensor. The system has a signal-to-noise ratio of 34 dB and thermal stability of 33.4 mV//spl deg/C. Conductivity images are reconstructed using the steepest-descent algorithm. Images obtained from isolated conducting tubes show that it is possible to distinguish two tubes separated 17 mm from each other. The images of different phantoms are found to be a good representation of the actual conductivity distribution. The field profiles obtained by scanning a biological tissue show the potential of this methodology for clinical applications.
84 citations