Author: John Mulindi
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DC Transmission and Distribution
In most cases, the dc power is obtained from large ac power systems by employing converting mechanisms like synchronous or rotary converters, solid-state converters and motor-generator sets and so forth. The reasons why power generation is done in ac form rather than dc are: How DC Power is Obtained from AC Power A general layout…
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Optothyristors: Features & Principle of Operation
Silicon Controlled Rectifiers (SCRs), Triacs and other solid-state devices used for switching larger voltages and currents ON and OFF are referred to as thyristors. Thyristors control switching in an ON-OFF way, in the same way to a light switch which is different from a transistor that can vary the amount of current in its emitter-collector…
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Zener Diode and Emitter-Follower/Series Voltage Regulators
Almost all electronic devices and circuits need a dc source of power for their operation. While batteries and dry cells can be used as a form of dc power supply, their voltages are usually low and they require frequent replacement; additionally they are costly compared to regular dc power supplies. The domestic ac supply can…
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PFDs vs. P&IDs
Process Flow Diagrams (PFDs) defines the major elements of the process schematically i.e. the interconnections of process vessels, pipes and flow paths of process fluids. On the other hand, Piping and Instrument Diagrams (P&IDs) shows the layout of all relevant process vessels, pipes and machinery but with instruments superimposed on the diagram showing what gets…
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Process Instrumentation Diagnostics & Communication Interfaces
There are various technologies that are available that help plant automation personnel to obtain diagnostic data which inform the type of maintenance to be undertaken. For example, using Distributed Control System (DCS), PC software tools, or handheld communicators, plant automation professionals can diagnose the health of an instrumentation device while it is in the line.…
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How a Bubbler Device is used for Level Measurement
An often utilized technique of indirectly measuring a liquid level is to measure the hydrostatic pressure at the bottom of the container. The level can then be extrapolated from the pressure and the specific weight of the liquid. This is the principle that a bubbler device operation is based on. Pressure is commonly used as…
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Megohmmeter: Function & Operation
The megohmmeter or megger is a portable deflection instrument widely used to check the insulation resistance of electrical cables and equipment. In other words, a megohmmeter can be described as a high resistance measurement instrument. The instrument has a constant high-voltage source, normally produced by a hand-cranked generator. The voltage may range anywhere between 100…
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Microwave Passive Components: Types & Functions
The part of the electromagnetic spectrum referred to as the microwave region loosely includes 1-300 GHz for practical purposes. These microwave bands are especially advantageous for transmission services such as satellite transmission, telephone transmission, broadcasting of commercial radio & television, and oil platform transmission. Some of the key advantages of microwaves are that the energy…
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Sources of Coherent Interference/Noise in Instrumentation Systems
Introduction The knowledge of how to design low noise instrumentation systems is an essential skill that any practicing instrumentation engineer should strive to learn because noise and interference affects any measurement system in one way or the other and this in turn affects the precision of measurements and the detectability of the quantity of measurement.…
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What is Optimal Control?
Optimal control is whereby the requirements are formulated as either the minimization of a cost index or the maximization of a performance index of an operational control system. Optimal control is utilized in a number of disciplines such as aircraft and spacecraft, satellites and aerospace, communications engineering, robots and robotics, electric drives, power systems, computer…