Monday, April 23, 2018

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What is the difference between a Transducer and a Transmitter

If someone would want a direct one sentence answer for this, it would be very difficult. The contrast between this two engineering terms has slowly been blurred overtime due to the advancement of technology.

The two terminology has slowly merged with new technologies being developed in the field industrial automation and controls in the specifics of process measurement.

Transducers basically are primary element sensors which converts mechanical energy to an electrical signal usually millivots. They are usually the one in contact with the environment or material itself to be measured.  A good example for this is the strain gauge. Some of the uses of strain gauges are for force measurement in machine tools, pressure sensors, strain measurement, tension sensors, impact sensors, torque measurement. Before, transducers are enough to make measurements of plant parameters and its output displayed on the field or near the equipment to with measurements taken. From the attached transducer to its visual indication, distances are rather short. But with the evolution of technology and automation, such as power plants and boiler operations, process instruments are now required to 'throw' the readings or outputs over long distances. The transducer's output of millivolts are needed to travel over long distances to the control rooms. That's where electronics come in to compensate signal loss due to resistance and other interference. Thus the transmitters where developed.        

Trasmitters are electronics that would allow the transducers millivolt signal output to be processed and converted to current for transmission over long distances. Since current are virtually unaffected by radio frequency interferences unlike voltage which are sensitive and to it and would add noise to its reading in addition to being intolerant to resistance, usually a two-wire transmitter is used with 4-20mA output. A three-wire transmitter has also been developed to have an output of 0-20mA signal.

In the early years of industrial automation, the transducers and the transmitters are entirely different terms but with research and developement, manufacturers started making single package instruments that is a transducer with embedded transmitter inside and its size becoming small due to advancement of electronics manufacturing. Some transducers nowadays have integrated circuits inside its packaging with size as small mobile phone SIM cards or even smaller. Before, transducers are wired to the transmitter and then sent to a controller, now, transducer/transmitter instrument can now be connected directly to controllers. 

So, before installing and using the instrument, read the manual carefully and  determine the correct output as the words transducers and transmitter are used inter-exchangeably by manufacturers depending on their choice. 


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