Types of Speed Transducers

Speed transducers are widely used for measuring the output speed of a rotating object. There are many types using different principles and most of them produce an electrical output.   Optical types These use a light beam and a light sensitive cell. The beam is either reflected or interrupted so that pulses are produced for each revolution. The pulses are then counted over a fixed time and the speed obtained. Electronic processing is required to time the pulses and turn the result into an analogue or digital signal. Magnetic Pick ups These use an inductive coil placed near to the rotating body. A […]

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Types of Pressure Transducers

Pressure sensors either convert the pressure into mechanical movement or into an electrical output. Complete gauges not only sense the pressure but indicate them on a dial or scale. Mechanical movement is produced with the following elements. · Bourdon Tube. · Spring and Piston. · Bellows and capsules. · Diaphragm. Bourdon tube The Bourdon tube is a hollow tube with an elliptical cross section. When a pressure difference exists between the inside and outside, the tube tends to straighten out and the end moves. The movement is usually coupled to a needle on a dial to make a complete gauge. It can […]

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Types of Temperature Transducers

Thermocouples When two wires with dissimilar electrical properties are joined at both ends and one junction is made hot and the other cold, a small electric current is produced proportional to the difference in the temperature. Seebeck discovered this effect. It is true no matter how the ends are joined so the cold end may be joined at a sensitive millivolt meter. The hot junction forms the sensor end. The picture shows a typical industrial probe with a flexible extension and standard plug. Thermocouples come in several forms. They may be wires insulated from each other with plastic or glass fibre materials. For high temperature […]

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What is Instrumentation?

The first question that popped up in my mind and raised to our professor during the first day of my instrumentation classes was that what is Instrumentation and how is it being used in process control?  “Simple, these are instruments that we  use in order to measure, satisfy and complete a given sequence that will control the process required ” my professor replied. then I taught, Duh! Instrumentation is not that complicated and might be a boring subject but then when he goes along introducing the different kinds of instruments that are involve in the process, then I started to get interested […]

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