Author: John Mulindi
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Technical Aspects of Foundation Fieldbus
Foundation fieldbus (FF) is an all-digital, serial, two-way communication system for industrial applications. Foundation fieldbus specifications include two different configurations: H1 and HSE. H1 Foundation Fieldbus (FF) H1 FF communication system is mainly applied to distributed continuous process control; running at 31.25 kbps. It connects digital field equipment such as sensors, actuators and inputs/outputs allowing…
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Topological Network Structures used in Fieldbus Systems
Topology is an important property of fieldbus. It is employed in the selection and definition of the best and suitable physical layout of the fieldbus network. The physical layer of the fieldbus has to meet somewhat demanding requirements like immunity to electromagnetic disturbances, robustness, intrinsic safety for hazardous areas, etc. The most important topologies for…
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Features of FM Receivers
FM receivers employ heterodyne principle. The FM broadcast signals lie in the frequency range between 88 MHz and 108 MHz. The intermediate frequency (IF) of a FM receiver is 10.7 MHz which is much higher than the IF value of 455 kHz in AM receivers. Let’s consider the block diagram of an FM receiver below:…
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What is Fieldbus in Industrial Communication Networks?
Fieldbus can be defined as a digital, serial, multidrop, data bus for communication with industrial control and instrumentation devices such as sensors, transducers/transmitters, actuators, local controllers, etc. Alternatively, Fieldbus can be defined as a digital, two-way, multidrop communication link among intelligent or smart measurement and control devices. It serves as a local area network (LAN)…
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Types of Insulators used in Power Systems
We have various types of overhead line and substation insulators. Generally they can be classified as: Post Insulators The post insulators comprise of pedestal posts and solid core cylindrical types. Pedestal post insulators The pedestal post insulator stacks employed in substations are available as single units with a range of lighting impulses withstand ratings (LIW)…
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The Conditioning of Thermocouple Sensor Voltages
Consider the circuit below: From the figure above, the sensing junction and reference junction are connected in series. When the junctions are at the same temperature the voltage output from the junctions is zero and the output from the amplifier is zero. When the junctions are at different temperatures, there is a differential voltage at…
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The Different Applications of Diodes
Diodes are used in many applications for example diodes are employed in reverse-polarity protection, used in voltage regulators, etc. We discuss these applications plus more in this article. Here are some of the different applications of diodes: Transient Suppression with Fly-back diodes Transient Protection When current flowing through an inductor is suddenly switched off, the…
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Features of HART Communication Protocol
HART is an acronym for (High Addressable Remote Transducer). HART is implemented in two ways in industrial instrumentation networks: Point to point system Multidrop system HART Point to Point System Here serial communication data is superimposed onto a standard 4-20 mA loop signal as shown in figure 1(a): Frequency shift keying (FSK) is used with…
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Semiconductor Diodes
A diode is a device that allows current to flow only in one direction. It is made from p-type or n-type semiconductors joined together. It has a depletion layer/p-n junction/potential barrier. How the depletion layer is formed The depletion layer is formed when a p-type and n-type are joined. The electrons in the n-type semiconductor…
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RTD 2, 3, 4 Wire Sensor Connections
The resistance temperature devices (RTD) can be connected directly to the controller peripheral amplifiers using 2-wire, 3-wire or 4-wire lead configuration. The wires in all these connections are in shielded cables. The RTD is usually driven from a constant current source (I) and the voltage drop (V) across the RTD is measured. RTD 2-wire connection…