Explanation for the functional elements of an instrument

1. FUNCTIONAL ELEMENTS OF AN
INSTRUMENT
PREPARED BY;
S.SANTHOSH KUMAR-EEE
SNS COLLEGE OF ENGINEERING
COIMBATORE 1

2. BLOCK DIAGRAM

3. *The variable that you
want to measure is mentioned here.
*It is called as the "Measurand“.
*For example, If you want to measure
current, then current is the measurand.

4. PRIMARY SENSING ELEMENT:-
The Primary Sensing
Element, as shown in the block diagram. You can
remember it better if i mention it as "First Sensing
Element". Thats right. The Element (Part) of an
instrument which makes first contact with the
measurand is called the primary sensing element. For
example, In Ammeter (which is used to measure
current), the coil carrying the current to be measured
is the primary sensing element.

5. VARIABLE CONVERSION ELEMENT:-
The output of the Primary
sensing element may not be suitable for the actual measurement
system. For example, in ammeter, the output from the coil is current, so
there we place a magnet to get a deflection due to the current passing
in the coil. So here the magnet acts as a variable conversion element,
converting current into physical movement which is the deflection and
by measuring the amount of deflection we can measure the amount of
current.
 Note:-
Some instruments do not need this variable conversion
elements, whereas some instruments need more than one.
Also keep in mind,
that the original information about the measurand must be retained
during the process of such conversion.

6. VARIABLE MANIPULATION ELEMENT:-
This is the tricky part.
The level of the output from the Variable conversion element may not
be enough for the next stage. For example, in case of ammeter if the
amount of current to be measured is so small , it may not be enough to
cause any deflection in the magnet. So here a transformer can be used
to increase the voltage to get enough deflection. So in this case the
transformer will be the Data Manipulation Element.
Note:-
The Variable conversion element and the variable
manipulation element are together called as Data conditioning element
since they help to obtain the signal in pure and acceptable form from
highly distorted form.

7. DATA TRANSMISSION ELEMENT:-
If the elements
of the system are physically separated, it is
necessary to transmit the data from one stage
to the other. So we need this Data Transmission
element. The data conditioning and the Data
transmission are together called as the
intermediate stage of an Instrument.

8. DATA DISPLAY ELEMENT:-
So now the measuring is
done and we need to present the data in a suitable form so
that it is easily understood by the observer and for this the
Data Presentation Element is used. In case of our Ammeter
Example, it is the Pointer and the scale arrangement that acts
as the Data presentation element. If the output data is to be
monitored, a visual display can be used and if needs to be
recorded then magnetic tapes , recorders or hard disk drives
can be used. The Data Presenting Stage may be called as the
Terminating stage of an instrument.