Digital sensors

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A digital sensor is an electronic or electrochemical sensor, where data is digitally converted and transmitted. Sensors are often used for analytical measurements, e.g. the measurement of chemical and physical properties of liquids. Typical measured parameters are pH value, conductivity, oxygen, redox potentials, and others. Such measurements are used in the industrialized world and give vital input for process control.

Sensor converter that measures a physical quantity and converts it into a signal

In the broadest definition, a sensor is a device, module, or subsystem whose purpose is to detect events or changes in its environment and send the information to other electronics, frequently a computer processor. A sensor is always used with other electronics.

Data conversion is the conversion of computer data from one format to another. Throughout a computer environment, data is encoded in a variety of ways. For example, computer hardware is built on the basis of certain standards, which requires that data contains, for example, parity bit checks. Similarly, the operating system is predicated on certain standards for data and file handling. Furthermore, each computer program handles data in a different manner. Whenever any one of these variables is changed, data must be converted in some way before it can be used by a different computer, operating system or program. Even different versions of these elements usually involve different data structures. For example, the changing of bits from one format to another, usually for the purpose of application interoperability or of capability of using new features, is merely a data conversion. Data conversions may be as simple as the conversion of a text file from one character encoding system to another; or more complex, such as the conversion of office file formats, or the conversion of image formats and audio file formats.

Developed country country with a developed industry and infrastructure

A developed country, industrialized country, more developed country, or more economically developed country (MEDC), is a sovereign state that has a developed economy and advanced technological infrastructure relative to other less industrialized nations. Most commonly, the criteria for evaluating the degree of economic development are gross domestic product (GDP), gross national product (GNP), the per capita income, level of industrialization, amount of widespread infrastructure and general standard of living. Which criteria are to be used and which countries can be classified as being developed are subjects of debate.

Contents

Sensors of analogue type were used in the past, but today more and more digital sensors are used. This article describes the difference between them and discusses the reason for the development of digital sensors.

General aspects

Digital sensors are the modern successors of analog sensors. Digital sensors replace analog sensors stepwise, because they overcome the traditional drawbacks of analog sensor systems (cf chapter 3)

History

Electronic and electrochemical sensors are typically one part of a measuring chain. A measuring chain comprises the sensor itself, a cable, and a transmitter. In the traditional analog systems, the sensor converts the measuring parameter (e.g. pH value) into an analog electrical signal. This analog electrical signal is connected to a transmitter via a cable. The transmitter transforms the electrical signal into a readable form (display, current outputs, bus data transmission, etc.).

The sensor and the cable often are not connected permanently, but through electrical connectors. This classical design with connectors and transmission of small currents through a cable has four main drawbacks: a) Humidity and corrosion of the connector falsify the signal. b) The cable must be shielded and of very high qualitiy to prevent the measuring signal from being altered by electromagnetic noise. c) The sensor can only be calibrated or adjusted when installed, because the influence of the cable (length, ohmic resistance, impedance) cannot be neglected. d) The cable length is limited.

Use and design

Digital sensors have been developed to overcome the traditional disadvantages of analog sensors. Digital sensors are mainly used in water, waste water and industrial processes. They measure parameters such as pH, redox potential, conductivity, dissolved oxygen, ammonium, nitrate, SAC, turbidity. A digital sensor system also consists of the sensor itself, a cable, and a transmitter. The differences to analog sensor systems are: a) The sensor has an electronic chip. The measuring signal is directly converted into a digital signal inside the sensor. The data transmission through the cable is also digital. This digital data transmission is not sensitive to cable length, cable resistance or impedance, and is not influenced by electromagnetic noise. Standard cables can be used. b) The connection between sensor and cable can be contactless and done by inductive coupling. Humidity and related corrosion is no longer an issue. Alternative fibre optic cables may also be an option for long or electromagnetically hostile connections. c) The sensor can be calibrated apart from the system.

Ammonium cation

The ammonium cation is a positively charged polyatomic ion with the chemical formula NH+
4
. It is formed by the protonation of ammonia (NH3). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary ammonium cations (NR+
4
), where one or more hydrogen atoms are replaced by organic groups (indicated by R).

Nitrate anion

Nitrate is a polyatomic ion with the molecular formula NO
3
and a molecular mass of 62.0049 u. Organic compounds that contain the nitrate ester as a functional group (RONO2) are also called nitrates.

Turbidity The cloudiness of a fluid caused by large numbers of particles that are generally invisible to the naked eye

Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality.

Related Research Articles

In telecommunication, a communications system or communication system is a collection of individual communications networks, transmission systems, relay stations, tributary stations, and data terminal equipment (DTE) usually capable of interconnection and interoperation to form an integrated whole. The components of a communications system serve a common purpose, are technically compatible, use common procedures, respond to controls, and operate in union.

Electromagnetic compatibility

Electromagnetic compatibility (EMC) is the branch of electrical engineering concerned with the unintentional generation, propagation and reception of electromagnetic energy which may cause unwanted effects such as electromagnetic interference (EMI) or even physical damage in operational equipment. Also, it is the ability of an equipment or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment. The goal of EMC is the correct operation of different equipment in a common electromagnetic environment.

Time-domain reflectometer

A time-domain reflectometer (TDR) is an electronic instrument that uses time-domain reflectometry to characterize and locate faults in metallic cables. It can also be used to locate discontinuities in a connector, printed circuit board, or any other electrical path. The equivalent device for optical fiber is an optical time-domain reflectometer.

Transmission line specialized cable or other structure designed to carry alternating current of radio frequency

In radio-frequency engineering, a transmission line is a specialized cable or other structure designed to conduct alternating current of radio frequency, that is, currents with a frequency high enough that their wave nature must be taken into account. Transmission lines are used for purposes such as connecting radio transmitters and receivers with their antennas, distributing cable television signals, trunklines routing calls between telephone switching centres, computer network connections and high speed computer data buses.

Coaxial cable A type of electrical cable with an inner conductor surrounded by concentric insulating layer and conducting shield

Coaxial cable, or coax is a type of electrical cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield. Many coaxial cables also have an insulating outer sheath or jacket. The term coaxial comes from the inner conductor and the outer shield sharing a geometric axis. Coaxial cable was invented by English engineer and mathematician Oliver Heaviside, who patented the design in 1880.

Data acquisition all methods of simultaneous or sequential time measurement and counting for measurable or quantifiable data and groups of contiguous data

Data acquisition is the process of sampling signals that measure real world physical conditions and converting the resulting samples into digital numeric values that can be manipulated by a computer. Data acquisition systems, abbreviated by the acronyms DAS or DAQ, typically convert analog waveforms into digital values for processing. The components of data acquisition systems include:

Antenna (radio) electrical device which converts electric power into radio waves, and vice versa

In radio engineering, an antenna is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies an electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves. In reception, an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be amplified. Antennas are essential components of all radio equipment.

A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another.

This is an index of articles relating to electronics and electricity or natural electricity and things that run on electricity and things that use or conduct electricity.

Electrical termination electronic circuit

In electronics, electrical termination is the practice of ending a transmission line with a device that matches the characteristic impedance of the line. This is intended to prevent signals from reflecting off the end of the transmission line. Reflections at the ends of unterminated transmission lines cause distortion which can produce ambiguous digital signal levels and mis-operation of digital systems. Reflections in analog signal systems cause such effects as video ghosting, or power loss in radio transmitter transmission lines.

Wattmeter

The wattmeter is an instrument for measuring the electric power in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements.

Dielectric spectroscopy measuring dielectric properties of medium

Dielectric spectroscopy measures the dielectric properties of a medium as a function of frequency. It is based on the interaction of an external field with the electric dipole moment of the sample, often expressed by permittivity.

This is an alphabetical list of articles pertaining specifically to electrical and electronics engineering. For a thematic list, please see List of electrical engineering topics. For a broad overview of engineering, see List of engineering topics. For biographies, see List of engineers.

Frequency domain (FD) sensor is an instrument developed for measuring soil moisture content. The instrument has an oscillating circuit, the sensing part of the sensor is embedded in the soil, and the operating frequency will depend on the value of soil's dielectric constant.

Time-domain reflectometry

Time-domain reflectometry or TDR is a measurement technique used to determine the characteristics of electrical lines by observing reflected waveforms. Time-domain transmissometry (TDT) is an analogous technique that measures the transmitted impulse. Together, they provide a powerful means of analysing electrical or optical transmission media such as coaxial cable and optical fiber.

Sensor node

A sensor node, also known as a mote, is a node in a sensor network that is capable of performing some processing, gathering sensory information and communicating with other connected nodes in the network. A mote is a node but a node is not always a mote.

Electronic engineering electrical engineering discipline which utilizes nonlinear and active electrical components to design electronic circuits, devices, and their systems

Electronic engineering is an electrical engineering discipline which utilizes nonlinear and active electrical components to design electronic circuits, devices, VLSI devices and their systems. The discipline typically also designs passive electrical components, usually based on printed circuit boards.

Many soil moisture measuring instruments are based on the principle of Amplitude Domain Reflectometry (ADR). This method measures the electrical impedance. Electromagnetic waves traveling along Transmission Lines (TL) enter in soil medium whose impedance is different from TL a part of the energy is reflected back to transmitter. The reflected wave interferes with incident wave and produces a standing wave along the TL, this changes the amplitude of wave along the TL. The impedance can be measured from difference in amplitude. The impedance has two components: electrical conductivity and dielectric constant. The effect of conductivity can be minimized by selecting an appropriate frequency.

Impedance microbiology is a microbiological technique used to measure the microbial number density of a sample by monitoring the electrical parameters of the growth medium. The ability of microbial metabolism to change the electrical conductivity of the growth medium was discovered by Stewart and further studied by other scientists such as Oker-Blom, Parson and Allison in the first half of 20th century. However, it was only in the late 1970s that, thanks to computer-controlled systems used to monitor impedance, the technique showed its full potential, as discussed in the works of Fistenberg-Eden & Eden, Ur & Brown and Cady.

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