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6) Data presentation element.
The principal functions of an instrument is the acquisition of information by Sensing and perception, the
process of that information and its final presentation to a Human observer. For the purpose of analysis
and synthesis, the instrument s are considered as systems (or) assembly of inter connected components
organised to perform a specified function. The different components are called elements.
1) PIMARY SENSING ELEMENT:
An element that is sensitive to the measured variable .The sensing element sense the condition , state
(or) value of the process variable by extracting a small part of energy from the measurement and
produces an output which is proportional to the input. Because of the energy expansion, the measured
quantity is always disturb. Good instruments are designed to minimise this loading effect.
2) Variable conversion (or) transducer element:
An element that converts the signal from one physical for to Another without changing the information
content of the signal.
Bourdon tube and bellows which transfer pressure into displacement.
Proving ring and other elastic members which converts force into displacement.
Rack and Pinion: It converts rotary to linear and vice versa.
Thermo couple which converts information about temperature difference to information in the
form of E.M.F.
3) MANIPULATION ELEMENT:
It modifies the direct signal by amplification, filtering etc., so that a desired output is produced.
[input]× constant = Output
4) DATA TRANSMISSION ELEMENT:
An element that transmits the signal from one location to another without changing the information
content. Data may by transmitted over long distances (from one location to another) or short distances
(from a test centre to a nearby computer).
5) DATA PROCESSING ELEMENT:
An element that modifies data before it is displayed or finally recorded. Data processing may be used for
such purposes as:
Corrections to the measured physical variables to compensate for scaling, non-linearity, zero
offset, temperature error etc.
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