A sensor typically measures temperature, humidity, flow, level or pressure. Sensorįirst, there needs to be some sort of sensor which measures a process variable. Related: Why a 0 mA Signal is Not Practicalįigure 4. Having a grasp on the history, workings, pros and cons of the 4-20 mA loop will help you to understand why it is the dominant standard for the industry and allow you to make informed decisions about your process control. Not knowing the basics could potentially cost you money when it comes time to make decisions about process display and control. Of all possible analog signals that can be used to transmit process information, the 4-20 mA loop is, by far, the dominant standard in the industry.Īs major as the 4-20 mA loop standard has become in the process control industry, many do not understand the fundamentals of its setup and use. Analog signals, where information about the process is transmitted via varying amounts of voltage or current, are the predominant type of input in industries requiring process control today.
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Thermocouples and RTDs provide direct temperature reading while digital signals such as Modbus ® provide exacting control over process variables and display. The M6 steel has high permeability and low losses, and it is used in high-performance applications.In the world of process control, there are a myriad of different types of process inputs. A few years ago, characteristics of silicon steel was altered with chemical changes, and today, the new product is known as AISI type M6. Silicon steel offers high saturation flux density. Silicon steel has high electrical resistivity and long-term performance stability. Nickel still offers high accuracy rating with a lower cost but does not have the performance terms of Silicon Steel cores. This metal is glassy or non-crystalline, making it useful for high performance transformers due to low conductivity. These ceramic materials serve as efficient insulators, and help decrease eddy currents. The ceramic materials are produced in different specifications to meet diverse electrical requirements. The magnetic cores made from ferrite ceramics are used in high-frequency applications. Ferrite ceramics are a class of ceramic compounds made from iron oxide, and one or multiple metallic elements. Ferrites are ceramic compounds of the transition metals with oxygen, which are ferrimagnetic but nonconductive.
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The ferrite qualities are available at low cost, which puts the high performance split core current transformers on the market at very attractive price. It is thus very important to understand the difference between the various technologies available, and make a choice according to specific application constraints.Ĭore Material Does the core material used matter?Ĭurrent sensors can be manufactured with many different types of core materials.
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The beauty of the split core transformers is that they can be retrofitted into a live installation without disturbing it, which often make them the unique choice for engineers designing power meters.īut these advantages have a price, making the split core current transformers more expensive and less accurate than the solid core transformers. They can be installed in electrical control panels – thus avoiding complex wiring – to remotely monitor devices that sometimes operate in inaccessible or harsh environments. Split-core current transformers can simply snap over a conductor, without the need to screw or weld on complex brackets, making installation and maintenance simple. stopping a production line, a telecom or datacenter power supply, some nuclear plant equipment, etc). Installing power metering systems is generally not possible, prohibitively expensive or even dangerous if it requires a service interruption, even for a short while (e.g. They are not suitable, however, for the numerous applications involving power monitoring of existing machines and facilities, where it would be necessary to shut down power and disconnect cables before retrofitting the solid core sensors in all the places where they might be used. Solid-core current transformers offer a cost-effective and accurate solution for designing power meters dedicated to new equipment and buildings.