Generalised measurement system and it's functional elements.

The video is for education and sits related to instrumentation and control system in Btech mechanical engineering stream.
The total explaination of generalised measurement system and it's functional elements.
Generalised measurement system and its functional elements:
1) Primary sensing element.
2) Variable conversion (or) Transducer element.
3) Manipulation of element.
4) Data transmission element.
5) Data processing element.
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.
Example:
Bourdon tube and bellows which transfer pressure into displacement.
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.
6) DATA PRESANTION ELEMENT:
An element that provides record or indication of the output from the data processing element. Ina
measuring system using electrical instrumentation, an exciter and an amplifier are also incorporated
into the circuit.
The display unit may be required to serve the following functions.
transmitting
Signalling
Registering
Indicating
recording
The generalised measurement system is classified into 3 stages:
a) Input Stage
b) Intermediate Stage
i. Signal Amplifications
ii. Signal Filtration
iii. Signal Modification
iv. Data Transmission
c) Output Stage
a) Input Stage:
Input stage (Detector-transducer) which is acted upon by the input signal (a variable to be measured)
such as length, pressure, temperature, angle etc. and which transforms this signal in some other physical
form. When the dimensional units for the input and output signals are same, this functional
element/stage is referred to as the transformer.
b) Intermediate Stage:
i. signal amplification to increase the power or amplitude of the signal without affecting its
waveform. The output from the detector-transducer element' is generally too small to operate an
indicator or a recorder and its amplification is necessary. Depending upon the type of transducer
signal, the amplification device may be of mechanical, hydraulic/pneumatic, optical and electrical
type.
ii. Signal filtration to extract the desired information from extraneous data. Signal filtration removes the
unwanted noise signals that tend to obscure the transducer signal. Depending upon nature of the signal
and situation, one may use mechanical, pneumatic or electrical filters.
iii. Signal modification to provide a digital signal from an analog signal or vice versa, or change the form
of output from voltage to frequency or from voltage to current.
Iv. Data transmission to telemeter the data for remote reading and recording.
c) Output Stage:
which constitutes the data display record or control. The data presentation stage collects the
output from the signal-conditioning element and presents the same to be read or seen and noted
by the experimenter for analysis. This element may be of:-
visual display type such as the height of liquid in a manometer or the position of pointer on a
scale.
numerical readout on an electrical instrument.
Graphic record on some kind of paper chart or a magnetic tape.
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