Tag: Industrial automation
-
Single-Phase & Three-Phase Inverters: Function and Operation
What is the Purpose of Inverters? Whereas dc machines are controlled by varying the voltage and current, ac machines are often controlled by varying the voltage and frequency. One way of accomplishing this is by using inverters. The process of converting ac from dc is referred to as inversion. Some of the reasons why ac…
-
Insulated Gate Bipolar Transistor (IGBT) – Structure, Operation & Applications
IGBT is a voltage controlled device. It has high input impedance like a MOSFET and low on-state conduction losses like a BJT. In other words, this power device combines the voltage control of the MOSFET gate with the superior conduction characteristics of the bipolar device. Nonetheless, the IGBT utilizes injected-charge modulation in the base region…
-
Telemetry in Instrumentation Systems
Telemetry can be defined as the science of gathering information at some remote location and transmitting the data to a convenient location to be examined and recorded. Importance of Telemetry Within instrumentation there is usually a requirement for telemetry in order to transmit data or information between two geographical locations. The transmission may be needed…
-
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…
-
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…
-
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.…
-
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.…
-
Pneumatic Signal Transmission System
Signal transmission in process instrumentation and control systems is largely done via electrical transmission but there are a few areas where pneumatic transmission of signals is vital especially where electrical signals or sparks can ignite combustible materials for example in petroleum refineries. In pneumatic transmission systems, the measured quantity (pressure, level, temperature, and so…
-
Phase Locked Loop High Precision Motor Speed Control System
AC generators can be utilized in high precision control systems. The AC generator rotor is rotated by the rotating shaft (i.e. the shaft from the motor being controlled). The output AC frequency is proportional to shaft speed. Zero crossings per time interval can be counted to determine speed for a simple control system. If high…
-
Principle of Operation of Magnetostrictive Position Sensors
Magnetostrictive sensors detect the location of a magnetic ring that slides along a conductive metal tube; in other words this sensor operation utilizes the effect of a magnetic field on magnetostrictive wire to function. The figure below illustrates a Magnetostrictive position sensor: To detect the position of the magnet (in this case, an electromagnetic created…