The measuring instruments they are defined as the
instruments or the device which is used for the measurement for example the
rulers the rulers are used for measuring the length so ruler is a type of
measuring instrument another example is like thermometer we use the thermometer
to measure the temperature so thermometer it is a type of measuring instrument
another examples are like weighing machine stop watches in the case of
engineering if we take the measuring instruments are like the emitter which is you
so measuring the current the voltmeter which is used for measuring the voltage
so measuring instruments they are the devices which are used for the
measurement of the unknown quantity like temperature pressure level
displacement voltage current okay
Definition of measuring instrument is
device which is used for measuring the unknown quantity not the various type of
measuring instruments they are classified into different categories and these
categories or the basis of this classification will be like whether they are
using what type of method of measurement these instruments are using and
whether these instruments are manually operated or they are self operated or
automatic instruments what type of parties instruments are using okay so these
instruments they are classified into different categories and we
are going to study about the classification of measuring instruments so let us
start with it we are having the first classification of measuring instruments
is absolute and secondary instruments so this type of classification of
measuring instrument into absolute in secondary instrument it is on the basis
that what method they are using like an absolute instrument the result of the
measurement or the unknown quantity it is measured in terms of the constants of
the instrument okay we are not getting directly reading the unknown quantity or
directly reading the values of the unknown quantity we are measuring it in
terms of the constants of the instrument whereas in secondary instrument we will
directly measure the value of the unknown quantity so just write the thing the
definition of these absolute and secondary instruments you so absolute
instruments they give the value of the measured measured is the unknown
quantity which we want to measure in terms of the instrument constant and its
deflection whereas the secondary instrument they give the magnitude of the
unknown quantity to be measured directly directly they will provide us the
value now if we talk about the example of the absolute instrument the tangent
galvanometer it is a type of absolute instrument because this tangent
galvanometer it provides the value of the unknown quantity in terms of its
constants like it will indicate the value you so here the tangent galvanometer
it is measuring the current and this galvanometer it is not directly giving us
the value of the current it will give its value in terms of the tangent of the
angle of the deflection produced the horizontal component of the Earth's
magnetic field the radius and the number of turns of the wire so it is
measuring the current but it is providing the value indirectly so this is a
type of absolute instrument another example is the release release current
balance so this release current balance it indicates the value of the current
in terms of the release constant so these are the example of absolute
instruments where the value of the measured it is in terms of the instrument
constant and it's deflection example of secondary instruments are like we are
measuring the current with the help of an ammeter so I'm Peter it will directly
indicate the value of the current it is giving directly the value of the
current to us by the pointer deflection over the scale so we can directly read
the value of the current from the instrument so it is a type of secondary
instruments now the secondary instruments they are also further classified into
three categories these three categories are indicating integrating and
recording instruments so secondary instruments they are classified into
indicating integrating and recording instruments in the indicating instruments
we have a pointer and this pointer is deflected over a calibrated scale so the
value of the measuring it will be indicated by the pointer deflection okay so
in the indicating instruments indicate the magnitude so
the indicating
instruments they indicate the magnitude of the unknown quantity when it is
being measured at the time of measurement and the value is directly indicated
on the steel and here it uses a pointer that moves over a calibrated scale so
these types of instruments are called the indicating instruments like in the meter in voltmeter in the meter watt meter all these instruments they have
a pointer and this pointer is deflected over the scale on the scale we have the
divisions so these divisions we can directly need the value from the scale so
at the type of measurement like suppose we are connecting a conductor with the
ammeter we want to measure the current across the conductor so we are directly
getting the value of the current through the scale next in the integrating
instrument we measure the value over a period like the over a period we are
measuring the value of the unknown quantity and those values they will be
summed up and then we will take the average value so integration is done over a
period of time or the area is calculated that is when the instruments are
called the integrating instrument you so integrating instruments they measure
the total amount of either the quantity of electricity provided over a period of
time or the amount of electrical energy supplied over a period of time so over
a period of time like suppose for one hour or two hours we are measuring that
how much electricity is supplied to the instrument so we are calculating the
total amount ere we are integrating the total amount or the total area under
the curve when we are measuring integration they are doing so those types of
instruments are all the integrating instruments like the instruments which
measure the power like energy meters and the ampere are meters so they measure
the amount of current which is supplied over one on or we measure the amount of
electricity supplied over one R so these instruments are all the integrating
instruments the third classification of the third type is the recording
instruments in which we record the value of the unknown quantity over a paper
and then because this type of recording is done because we want to analyze the
value of the unknown quantity like if any variation is coming out in the value
so reporting is done of the measurement like we use a pen and then this pin is
connected with the measuring value so this pin will move over a paper and
continuously we are recording the values of the unknown quantity you so the
recording instruments they keep a continuous record of the variations in the
magnitude of the unknown quantity like for example we have the recording
instruments like the recording voltmeter we are having or the the instruments
in which the paper is used on which a continuous record is taken okay so the
first classification is the absolute and the secondary instruments secondary
instruments further classified into indicating integrating and recording now
next classification of measuring instruments is on the basis of the signal used
by them like analog and digital instruments so if the output of the instrument
it is an analog signal in the analog form so that will be an analog instrument
and if the output of the instrument it is in digital form so the instrument is
called a digital instrument you so if the output of the instrument it is in the
analog form so that will be called an analog instrument and output means analog
signal is a signal in which the values of the quantity it is continuously
varying with the time so in if the signal is provided in a continuous fashion
like if we draw a signal this is the time and this is the amplitude of the
signal so in this type of signal will be called an analog signal here the value
of the signal is varying at every instant of time so if this type of output is
provided by the instrument that will be called analog instrument whereas
digital instruments they give a digital output means the output will be in the
form of discrete steps if we draw or digital signal this will be the amplitude
again here we will have the time so suppose at this instant its value is this
at this instant its value is this so if in this way the signal is changing that
will be called a digital signal that means in the form of discrete steps we are
having so this it depends upon the type of output given by the instrument if
it's an analog output that will be an analog instrument if it is a digital
output then we have the digital instruments example of analog instruments are
like analog ammeter analog voltmeter in which we are having the instrument here
we will have the pointer and this pointer is deflected over the skin okay so
these are the type of analog instruments in digital instrument like digital
multimeter we get the diary reading over the LCD like suppose if we are
measuring the current so we will directly get the value one ampere on the LED
on this screen of the digital multimeter so these types of instruments are
digital instruments next classification of instrument is based upon the process
like if it involves a mechanical process then they are called mechanical
instrument electrical instruments and electronic instruments you now in the
instrument we get the value of the unknown quantity with the help of a pointer
now when this pointer it will be deflected due to some mechanical process the
instruments are all mechanical instruments if the pointer is deflected due to
some electrical process those instruments will be called electrical instruments
and the instruments in which the pointer is deflected due to some electronic
mechanism
then those instruments are called electronic instruments like for
example mechanical instruments like if we have two galvanometer in the
galvanometer the pointer is deflected due to the movement of the coil this coil
is placed in the magnetic field of a magnet and you do that magnetic field when
the magnetic field it changes from strong to weak the pointer will be deflected
and the coil is rotated so due to the rotation of the coil the pointer is
deflected over a scale so that is a type of mechanical instruments so we can
say that in mechanical instruments you the pointer is deflected due to some
mechanical process now these mechanical instruments they are somewhat heavy
because mechanical parts are involved in them and because these mechanical
parts they are very heavy and friction is caused between these first so these
instruments they are very slow in process so the pointer is deflected very
slowly and the value or the readings we can take from the instrument that a
deflection is very slow so they are slow in their working now electrical
signals here you do some electrical process if the pointer is deflected then
those instruments are all the electrical instruments so when a pointer is
deflected you do some electrical activity like when we are measuring the current
through the ammeter so due to the current flowing through the ammeter the
pointer is deflected okay so these types of instruments are all the electrical
instruments amita of voltmeter the ohmmeter all these are electrical
instruments in the electronic instruments dude they are the semiconductor
devices in which we have the electrons are involved so due to the movement of
electrons the pointer is moved over a scale okay due to movement it Tron's the
pointer is deflected so you some semiconductor activity is involved that is why
these are known as electronic instruments example is like the CRO that is the
cathode ray oscilloscope in the cathode ray oscilloscope we have the electrons
these electrons are excited and they are placed in between a cathode and anode
and due to which a magnetic field is present and due to the magnetic field due
to the presence of the magnetic field the electrons are deflected so due to the
movements of electrons we have a pointer which moves on the cathode ray
oscilloscope screen and on that screen the pointer moves over the skin so the
movement of pointer is caused due to the movement of electrons due to the
presence of electrons so electronic instruments example is CRO for mechanical
instruments we were having the example of galvanometer and electrical
instruments we are having the example of ammeter and voltmeters so this is a
type of classification of instruments based on the activity involved which is
causing the deflection of the pointer over the calibrated scale the next classification
of instruments is manual and automatic instruments you so as the name suggests
and manual instruments those instruments which are manually operated means we
need an observer and that observer is going to keep a record of the readings of
the instrument so here always an observer is required to measure the values
whereas automatic instruments they do not need the presence of an observer they
will directly give us the value the value will be indicated by the instrument
okay so manual operated instruments so manual instrument if we talk about its
example the example is a resistance thermometer incorporating a
wheatstonebridge so in this mechanism resistance thermometer we are measuring
the resistance by using the temperature okay so resistance thermometer we need
an observer to keep a record of the temperature readings that observer is going
to keep is going to make a table for the temperature measurement and then the
resistance will be measured okay so manual instruments they are so manual
instruments they always need the service of an operator whereas automatic
instruments they do not require the service of an operator example of this is a
glass tube thermometer in the glass tube thermometer no operator is required
the mercury will be deflected and through the deflection or the level of the
mercury mercury we can directly read the value of the temperature so this is
the classification based upon the presence of the operator is whether it is
required or not required next classification of instrument is based upon the
power used by the instrument whether the instruments they are self operated or
they are power operated you so in self-operated instruments no outside power is
required for the operation of the instrument for example the dial type indicating
instrument in these instruments we directly connect the instrument in the
socket and the instrument it will not require any type of power it will
directly indicate the value of the measurement so here in self operated
instrument no outside power is required for the operation of the instrument
there as in power operated instruments the some type of external power is
required for the operation like electricity's pro used and also some compressed
air or hydraulic air supply is also required so there are some external part is
required for the operation of the instrument that is why they are called power
operated instrument example of such instruments are the electromechanical
instruments in the electromechanical instruments electricity is provided and
you do that electricity the magnetic field is generated and due to that
magnetic field the pointer is deflected so here some external part is provided
so that the instrument can work okay so that is why it is called power operated
instrument some external power is required whereas dial type indicating
instruments in that you can see that when we connect those instrument in the
circuit no power is required we can it can directly give us the value of the
unknown quantity like when we are measuring voltage what we do we connect the
voltage in parallel with the conductor across the conductor and it will give us
the value of the voltage okay so it is not using any type of part that is what
is called self operated instruments now next classification of instrument is
based upon the type of method they are using for the measurement like if they
are using the deflection method and the null method in the deflection method we
will have a pointer in the instruments and that pointer will indicate the value
of the measuring quantity whereas the null methods we have null value okay we
are going to make a value nullified so that like in the bridge is reused in the
wheatstonebridge we are measuring the resistance by making the value across the
galvanometer as zero so when the galvanometer indicates null deflection then we
can measure the we can say that the bridge is balanced and we can measure the
unknown resistance so next classification is deflection and null output
instruments you so the next type is the null output
instruments so I now put
instruments you in these instruments are zero or the null indication it will
lead to the determination of the magnitude of the unknown quantity let's take
example of these two types the deflection instruments examples are the PM MC
instruments that is permanent magnet moving coil instruments okay permanent
magnet instruments in these instruments a coil is present in between a magnet
electricity is provided and due to that electrical field a magnetic field is
generated due to the magnet and the coil in between the magnet it is magnetized
okay so due to the movement of the coil the pointer which is connected to the
coil that is deflected over the calibrated scale so the value of the unknown
quantity it is measured due to the mechanical movement and that mechanical
movement of the pointer is caused due to the activity offer due to the movement
of the hole so example of deflection instrument is TM MC instrument that is
permanent magnet moving coil instruments okay so here we will have a coil and
this coil is placed between the magnet north and the south poles of the magnet
and to the coil a pointer is connected okay so when this coil moves between
this magnetic field pointer is deflected over the scale so we can read the
value of the current by the reading the values on the skin so your deflection
of the instrument indicates the measurement of the unknown quantity whereas in
the null output instruments like an example of the DC potential made up in that
DC potentiometer what we do we have the slidewire potentiometer in which we
move the key or knob over the slidewire and when the galvanometer the / it
shows zero deflection it means that the resistance or the EMF of the standard
cell and the unknown EMF they are equal to each other so we are measuring the EMF
by checking the null condition of the galvanometer also in the case of beat
stone bridge in the Wheatstone bridge also we measure the resistance and this
resistance is measured when the bridge is balanced and balanced condition
occurs when the galvanometer it shows zero or or not deflection so zero and
null indication it leads to the determination of the magnitude of the unknown
quantity so example is now being stone bridge and the DC slide by a
potentiometer okay so this was the classification of the instruments if we draw
a flowchart for the classification of instruments it will be like measuring
instruments first classification be studied was absolute and secondary
instruments secondary instruments they were further classified into indicating
integrating and recording next classification be studied was analog and digital
next we studied the classification mechanical electrical and electronic next
classification we studied was manual and automatic next we studied self
operated and are operated and in the last we studied the classification
deflection and neural operated instruments so this is how the measuring
instruments they are classified this is the flowchart for it okay different
classifications are they're based on different criterias okay so in this article we studied the classification of the measuring instruments we studied the
different categories of measuring instruments so I hope that this topic is
clear to you....
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