205--MI Lab Manual by Prof. N.J.Kumbhar
Experiment No. 1
Object
Measurement of resistance by ammeter voltmeter method.
Objectives
To measure the
unknown resistance.
Apparatus
Sr.No.
|
Apparatus
|
Range
|
Type
|
Quantity
|
1
|
Ammeter
|
(0-2.5) A
|
MI
|
1
|
2
|
Voltmeter
|
(0-300) V
|
MI
|
1
|
3
|
Rheostats
|
600Ω, 1 A
|
Wire Wound
|
1
|
4
|
Connecting
Wires
|
2.5sq.mm.
|
Copper
|
Few
|
Procedure
1)
Connect the circuit diagram as Shown in figure.
2)
Switch on the power supply.
3)
Keep Rheostat in minimum position.
4)
Note down the values in the various meters.
5)
Vary the rheostat.
6)
Note down the values in the various meters.
7)
Now calculate the values of unknown resistance.
Circuit
Diagram
Observation Table
Sr.
No.
|
VL
Volt
|
Il
Amp
|
Calculated
Resistance R
Ohm
|
Observed
Resistance R
ohm
|
1.
|
||||
2.
|
||||
3.
|
||||
4.
|
||||
5.
|
||||
6.
|
Hand Calculation:
Result
Thus we have studied the measurement of resistance by using
V-I method.
Questions
1.
Explain with neat diagram working of attraction type moving
iron instrument.
2.
Explain with neat diagram working of electrodynamometer type
wattmeter.
Experiment No. 2
Object
Measurement
of Reactive Power by one wattmeter with all possible connectionsof current coil
and pressure coil.
Objectives
To understand:
1)
The working principles of wattmeter.
2)
Definitions of active and reactive power.
3)
Meaning of Balance three phase load.
4)
To connect the one wattmeter to measure the reactive power in
three phase balance circuit.
5)
To compare practical obtained reading with theoretically
calculated for the correctness.
Theory
Reactive power measurement in 3 phases circuit using one
wattmeter:
In this
method current coil
of wattmeter is
connected to any
one line and
pressure coil is connected across remaining two lines, the
connection is as shown in the circuit diagram,
W = ICVPC Cos
(IC^VPC)
= IRVYB
Cos (IR^VYB)
To find IR^VYB assume load to be star
connected having Cosφ lagging p.f.The
phasor diagram is as shown below:
VYB = VY-VB
IR^VYB = 90-φ
W = IRVYB Cos (90- φ)
W = IRVYBSinφ
= VLILSinφ
Thus the wattmeter reading isW = VLILSinφ
Total reactive
power = -√3 W
Apparatus
Sr.No.
|
Apparatus
|
Range
|
Type
|
Quantity
|
1
|
Wattmeter
|
(10A/600V)
|
MC
|
1
|
2
|
Voltmeter
|
(0-600)V
|
MC
|
1
|
3
|
Ammeter
|
(0-10A)
|
MC
|
1
|
4
|
Load bank
|
R-L
|
||
5
|
Connecting Wires
|
2.5sq.mm.
|
Copper
|
Few
|
Procedure
1)
Make the connections as shown in the
circuit diagram.
2)
Keeping the some load, switch on the supply
3)
Note down the wattmeter other meter readings.
4)
Turn off the supply.
5)
Now calculate the value of reactive power using the formula.
Circuit Diagram
Reactive power measurement:
Observation Table
Observations
|
|||||||||
Sr. No
|
|||||||||
VL
|
IL
|
W
|
Total Reactive power (Var) Q= -√3 W
|
Power
Factor
CosΦ
|
|||||
(Volt)
|
(Amp)
|
(Var)
|
|||||||
1.
|
|||||||||
2.
|
|||||||||
3.
|
|||||||||
Calculations
Voltmeter reading
|
& Ammeter reading
|
=
-------
|
&-----------
|
|||
Wattmeter Reading W = _______
|
||||||
Power factor CosΦ = Cos {tan-1(√3(W2-W1)/(W1+W2))}=
_______
[From previous circuit diagram for same load condition]
Sin Φ =_________
P= √3VISinΦ= Reading of the
wattmeter= _________ Var
Hand Calculation:
Result:
Reactive power =__________ Var
Conclusion:
One wattmeter is enough to measure reactive power in the 3
phase circuit accurately.
Questions
1.
Derive the equation to calculate value of multiplier.
2.
State essential requirements for of multiplier.
3.
Explain how one wattmeter can be used to measure reactive
power in three phase balanced load.
Experiment No. 3
Object
Title:Measurement of
Active & reactive power in three phase circuit using two wattmeter method
(Balanced & Unbalanced Loads).
Objectives
To understand:
1.
The working principles of wattmeter.
2.
Definitions of active and reactive power.
3.
Meaning of Balance three phase load.
4.
To connect the two wattmeter to measure the active and
reactive power in three phase balance circuit.
5.
To compare practical obtained reading with theoretically
calculated for the correctness.
Theory
Two
wattmeter method:
This is generally used method for
measurement of power in 3 phase, 3 wire load circuit. This method can be used
for unbalanced and balanced loads. The current coil of 2 wattmeter’s are
inserted in any 2 lines and pressure coils are connected from its own current
coil to the line without current coil.If W1 and W2 are
the 2 wattmeter readings then the total power is
W= W1+W2
In case of balanced load the power factor can be calculated
from W1 and W2 readings for balance lagging power factor
load.
W1 = VLIL Cos (30-φ)
W1 =
VLIL Cos (30+φ)
W1+W2
= √3 VLIL Cos φ (1)
W1-W2
= VLIL [Cos (30-φ) - Cos (30+φ)]
=VLIL[(Cos30Cosφ)+(Sin30Sinφ)− (Cos30Cosφ)+(Sin30Sinφ)]
= VLIL[2Sin30Sinφ]
= VLIL[2x1/2xSinφ]
W1-W2 = VLILSinφ
Taking ratio of (1) and (2)
W1-W2VLIL
Sin φ
=
W1+W2
√3VLILCosφ
√3 (W1-W2)
tanφ
=
=
(W1+W2)
√3 (W1-W2)
Φ= tan -1
(W1+W2)
Therefore power factor
[tan-1 √3 (W1-W2)]
Cos φ =Cos
(W1+W2)
For balanced load:
Let us consider the rms values of the currents and voltages
to prove that the sum of the two wattmeter gives total power consumed by three
phase load.
W1 = IR x VRB x Cos(IR^VRB)
W2 = Iy x VRB x Cos (IY^VYB)
To find the angle between (IR and VRB)
and (IY and VYB). Let us draw phasor (assuming load power
factor be Cos φ lagging.
VRB
=VR – VB and
VYB = VY – VB
VR ^
IR = φ and VY
^ IY= φ
VR = VY =VB = VPH
|
&
|
VRB = VYB = VL
|
|
IR = IY= IB = IPH
|
|
IR ^ VRB = (30 -φ)
|
And
|
IY ^ VYB = (30 + φ)
W1 =
IRVRB Cos (30 -φ)
= VLIL Cos (30 -φ)
W2 = IYVYB Cos (30 +φ)
=VLIL Cos (30 + φ)
W1+W2 = VLIL
[Cos (30-φ Cos (30+φ
=√3VLILCosφ
Total active
power = √3VLILCosφ
Total reactive power = √3VLILSinφ
Apparatus
Sr.No.
|
Apparatus
|
Range
|
Type
|
Quantity
|
1
|
Wattmeter
|
(10A/600V)
|
MC
|
1
|
2
|
Voltmeter
|
(0-600)V
|
MC
|
1
|
3
|
Ammeter
|
(0-10A)
|
MC
|
1
|
4
|
Load bank
|
R-L
|
||
5
|
Connecting Wires
|
2.5sq.mm.
|
Copper
|
Few
|
Procedure
1)
Make the connections as shown in the figure.
2)
Switch on the 3 phase power supply.
3)
Apply the load confirm that all three ammeters read same
reading for balance load.
4)
Note down the values in the various meters.
5)
Turn off the 3 phase supply.
6)
Now calculate the value of the active and reactive power
using the formulae.
7)
Theoretical values are calculated and compared with the
experimental values.
Circuit diagram
Active power measurement:
Observation Table
Sr.No
|
Load
IL
(Amp)
|
Supply VL
(Volt)
|
Wattmeter
Reading (Watts)
|
Total Power
W= W1+W2
(Watts)
|
Power Factor
cosФ=W /√3VLIL
|
Active
Power W =√3VLILcosФ
(Watts)
|
Reactive
PowerW =√3VLILSinФ
(VAR)
|
|
W1
|
W2
|
|||||||
1
|
||||||||
2
|
||||||||
3
|
||||||||
4
|
||||||||
Sample Calculations
Line current IL=
_____
Amps Line
voltage VL= -----------------
Wattmeter Readings W1______Watts W2
=_______Watts
Power factor CosΦ = Cos {tan-1[√3(W2W1)/(W1+W2)]}
=______
Active power P= √3 VLILCosΦ =
___________Watts = W1 +W2
Reactive power = R=√3 VLILSinΦ______________VAR
Hand
calculations:
Result
Average Active Power
P=…………..Watt
Average Reactive Power Q =……………VAR
Conclusion
We can measure the power in three phase circuit using two
wattmeter for different load conditions.
Questions
1.
State various errors introduced in measurement of electrical
quantities.
2.
Define standard & give its classification.
3.
State the necessity of extension of range of voltmeter.
4.
What is multiplier?
5.
Write short note on reactive power measurement of three phase
circuit.
Experiment No. 4
Object
To measure the
resistance of a given specimen in medium resistance range by usingWheatstone
bridge.
Objectives
To understand
1)
Classification of resistance based on measurement.
2)
Different methods of
medium resistance measurement.
3)
Working Wheatstone bridge.
Apparatus
Sr.No.
|
Apparatus
|
Range
|
Type
|
Quantity
|
1
|
Wheatstone bridge Kit
|
|||
2
|
Unknown R
|
1
|
||
3
|
D.C. Power pack
|
1
|
||
4
|
Connecting Wires
|
Copper
|
Few
|
Procedure
1)
Make the connection as per circuit diagram.
2)
Switch on the supply of D.C. Power pack and apply 3volt to
bridge.
3)
Set convenient value of P/ Q ratio.
4)
Vary the resistance of standard arm ‘S’ until galvanometer
shows zero deflection.
5)
Repeat above procedure for different value of P/ Q ratio.
6)
Tabulate the reading and workout unknown resistance of
spaceman connected by using formula R= P/ Q x S.
7)
Repeat all above procedure for different unknown specimens.
Circuit
Diagram
Observation Table
Sr.
No.
|
P
ohm
|
Q
Ohm
|
S
Ohm
|
Calculated
Resistance R ohm
|
Observed
Resistance R ohm
|
1.
|
|||||
2.
|
|||||
3.
|
|||||
4.
|
Hand Calculations:
Conclusion
From this experiment we can
calculate the unknown resistance and compared with the observed resistance.
Questions
1)
Which are the different methods of measuring unknown resistance?
2)
Explain with neat diagram Wheatstone bridge for measurement
of unknown resistance.
3)
What are the types of Wheatstone bridge?
Experiment No. 5
Object
Measurement
of inductance using Maxwell Bridge.
Objectives
To understand different types of measurement of parameters of
circuit (Null and deflection method), importance of null deflection method of
measurement and to understand the suitability of the bridge for the low Q
factor.
Theory
Maxwell’s bridge explanation:
Let L1=
unknown inductance
R1= effective resistance of inductor L1
R2, R3, R4= known
non-inductive resistances
C4=variable standard capacitor
D=Detector
Operation:
This method is very suitable for accurate measurement of
medium inductances. In this method unknown inductance is determined by
comparing it with a standard variable capacitance. Such a bridge circuit is as
shown in the figure.
For balance condition of bridge:
Z1Z4=Z2Z3
(R1+jwL1)R4/ (1+jwC4R4)=R4
Or R1R4+jwL1R4= R2R3+jwC4R4R2R3
Equating real and imaginary quantities
R1R4=R2R3
Or
|
R1=R2R3/R4
|
And
|
jwL1R4=jwC4R4R2R3
|
Or
|
L1=C4R2R3
|
The bridge is preferably balanced by varying C4 and R4.
The Q factor of the inductor is given by wL1/R1 and at
balance condition
Q=wL1/R1=wC4R4
ADVANTAGES:
1) The two
balance equations are independent if we choose R4 and C4
as variable elements.
2)
The frequency does not appear in any of the two equations.
3)
This bridge is very useful for measurement of a wide range of
inductance at power and audio frequency
Apparatus
Sr.No.
|
Apparatus
|
Range
|
Type
|
Quantity
|
1
|
Maxwell Bridge Kit
|
|||
2
|
Unknown L
|
1
|
||
3
|
D.C. Power pack
|
1
|
||
4
|
Connecting Wires
|
Copper
|
Few
|
Procedure
1)
Make the connection as per circuit diagram.
2)
Switch on the supply of D.C. Power pack and apply 3volt to
bridge.
3)
The bridge is preferably balanced by varying C4 and R4.
4)
Until galvanometer shows zero deflection.
5)
Tabulate the reading and workout unknown inductance of
spaceman connected by using formula L1=C4R2R3.
6)
Repeat all above procedure for different unknown specimens.
Circuit
Diagram
Observation Table
Sr.
No.
|
R2
ohm
|
R3
ohm
|
R4
ohm
|
C4
Micro
-farad
|
Calculated Inductance
L Henry
|
Observed Inductance
L Henry
|
|
1
|
|||||||
2
|
|||||||
Hand Calculations:
Conclusion:
From this experiment we can
calculate the unknown inductance and compared with the observed inductance.
Questions
1.
Which bridge is used to measure unknown inductance?
2.
With neat circuit diagram derive the balancing condition for
Maxwell’s inductance bridge.
3.
What is Q factor?
Experiment No. 6
Object
Measurement of
Capacitance by using Schering Bridge.
Objectives
To study Schering bridge and measure unknown capacitance.
Theory
A very important bridge used for the precision measurement
capacitance & their insulating properties in the Schering Bridge its basic
circuit arrangement is shown in figure. The standard capacitor is supposed to
be high quality mica capacitor (low costs) for general measurement or an air
capacitor for insulation measurement. For balance the general equation,
Z1Z4 =Z2Z3 (1)
Z1
= [R1 * (1/ jωc1)] / [R1 + (1/ jωc1)]
Z2 = R2
Z3
= 1/ jωc3
Z4
= Rx + (1/ jωcx)
From equation (1)
[R1 * (1/ jωc1)]/[ R1 + (1/
jωc1 )]*( Rx + (1/ jωcx)) = R2 *
(1/ jωc3)
[R1/ ( jωc1 R1+ 1)]*( Rx
+ (1/ jωcx)) = (R2 */ jωc3)
R1*Rx+(R1/ jωcx) =
(R2 */ jωc3)*( jωc1 R1+ 1)
R1*Rx+(R1/ jωcx)
= (R2 */ jωc3)*( jωc1 R1+ 1)
R1*Rx+(R1/ jωcx)
= (R2 */ jωc3)*( jωc1 R1+ 1)
By equating real and imaginary parts, we get
Rx= R2C1/C3 &Cx = R1C3/R2
In our system we have made C3 a
variable capacitor using rotary s/w Both R1 &R2 are made variable by using
equationhim helical post (10 K each) the bridge is widely used for gating small
capacitor at low voltage with good precision. Rx is assumed to be negligible
small for good quality capacitance & hence, no provision for c1 is made.
FORMULA:
Cx = R1/R2×C3, if R1=2.2k, R2=1k,
C3=0.1 then
Cx = 2.2k/1k×0.1mfd=0.22mfd.
Apparatus
Sr.No.
|
Apparatus
|
Range
|
Type
|
Quantity
|
1
|
Schering Bridge Kit
|
|||
2
|
Unknown C
|
1
|
||
3
|
D.C. Power pack
|
1
|
||
4
|
Connecting Wires
|
Copper
|
Few
|
Procedure
1)
Make the connection as per circuit diagram.
2)
Switch on the supply of D.C. Power pack and apply 3volt to
bridge.
3)
In our system we have made C3 a variable capacitor using
rotary s/w
4)
Both R1 &R2 are made variable.
5)
Until galvanometer shows zero deflection.
6)
Tabulate the reading and workout unknown capacitance of
spaceman connected by using formula Cx=R1/R2×C3.
7)
Repeat all above procedure for different unknown specimens.
Precautions
1)
Operate ten ohm very carefully.
2)
Ensure firm connection across terminals for capacitance.
3)
You may also use external signal sources in the range 5 to 10
voltage.
Circuit Diagram
Observation Table
Sr.
No.
|
R1
ohm
|
R2
ohm
|
C3
Micro
–farad
|
Calculated Capacitance
Micro -farad
|
Observed Capacitance
Micro -farad
|
|
1
|
||||||
2
|
||||||
Sample Calculations
FORMULA:
Cx = R1/R2×C3, if R1=2.2k, R2=1k,
C3=0.1 then
Cx = 2.2k/1k×0.1mfd=0.22mfd.
Hand Calculation:
Conclusion
From this experiment we can
calculate the unknown capacitance and compared with the observed capacitance.
Questions
1.Schering Bridge is used to find
out.
2.What is dissipation factor?
3.Explain Schering Bridge.
Experiment No. 7
Object
Linear Variable Differential
Transformer.
Objectives
Measurement of displacement by using Linear Variable Differential
Transformer.
Theory
The Linear
Variable Differential Transformer (LVDT) is a displacement transducer similar
in appearance to a linear potentiometer; however, the mechanism by which it
operates is very different. LVDT’s tend to be much more expensive than pots and
offer significant advantages in longevity, friction, and linearity.
Apparatus
Sr.No.
|
Apparatus
|
Range
|
Type
|
Quantity
|
1
|
L.V.D.T kit,
|
|||
2
|
Connecting Wires
|
2.5sq.mm
|
Copper
|
Few
|
Procedure
1.
Connect the terminals
marked “PRIMARY” on the front panel of the instrument to the terminals marked
“PRIMARY” on the transducer itself, with the help of the flexible wires
provided along with. Observe the colour code for the wires provided and the
colour of the binding posts.
2.
Identically establish
connections from terminals marked “SECONDARY”. Observe the colour code for the
wires provided and the colour of the binding posts.
3.
Keep pot marked “MAX”
in most anticlockwise position.
4.
The magnetic core may
be displaced and the pointer may be brought to zero position. If the DPM is not
indicating zero, use potentiometer marked “MIN” to get a zero on DPM at zero
mechanical position. If the core is displaced in both directions, the meter
must show indications with appropriate polarity. Now displace the core to 19 mm
positions in one of the directions .Adjust the “MAX” pot to get an indication
of 19.00 on the DPM under this condition. Now the set up is ready for
experimentation. You may again check for zero position also.
5.
Now the core can be
displaced by a known amount in the range of +19 and -19 mm and the meter
readings can be entered in the table given below. It may noted that by inter
changing the secondary terminals or the primary, the polarity of the meter
indication can be reversed for a given direction of input displacement.
6.
For LVDT provided with
dial gage (range 0 to 10mm or 0 to 25 mm
or 0 to 20 mm), adjust the magnetic core carefully by rotating the control knob in the clockwise direction. Note that for this
type (Dial gage type) arrangement, displacement in only one direction i.e.
positive direction is possible. Operate the control knob very carefully.
7.
Plot the graph of input
displacement and the output indication on the X and Y axis respectively.
Output Waveform:
Observation Table
Sr.No.
|
Displacement towards right
in mm
|
Indicated Displacement
in mm
|
Displacement towards left
in mm
|
Indicated Displacement
in mm
|
Conclusion
Thus we measured displacement non electrical parameter by
using LVDT
Questions
1.Explain the
working of LVDT.
2.What are the
advantages and disadvantages of LVDT?
3.What are the
applications of LVDT?
Experiment
No. 8
Object
Calibration of Single phase Induction type energy meter at
different power factors.
Objectives
To learn the construction and working of single phase
induction type energy meter, to connect the energy meter in the supply circuit
and also to calibrate the energy meter for different load condition ( by
listing the errors and carrying out the adjustments in energy meter to minimize
the errors).
Apparatus
Sr.No.
|
Apparatus
|
Range
|
Type
|
Quantity
|
1
|
Wattmeter
|
(10A/600V)
|
MC
|
1
|
2
|
1 ph energy meter
|
1
|
||
3
|
Voltmeter
|
(0-600)V
|
MC
|
1
|
4
|
Ammeter
|
(0-10A)
|
MC
|
1
|
5
|
Load bank
|
R-L
|
1
|
|
6
|
Connecting Wires
|
2.5sq.mm.
|
Copper
|
Few
|
Procedure
1)
Make the connections as shown in the circuit diagram.
2)
Adjust the supply voltage to rated value.
3)
Apply 10% of the rated load (approx 1-2amps)
4)
Note down the all meter reading and time taken for 10
rotations of the disc of energy meter.
5)
Tabulate the reading and workout the % error
6)
If error is greater than 10% then carryout the light loads
adjustment to reduce the error less than the 10%.
7)
Now apply 90% of the rated load (approx 8.5 to 9.5amps).
8)
Note down the all meter reading and time taken for 10
rotations of the disc of energy meter.
9)
Tabulate the reading and workout the % error
10) If error is
greater than 10% then carryout the top load adjustment(brake magnet position
adjustment) to reduce the error less than the 10%.
11) For different
load condition note down all meter reading and time for 10 rotations of disc.
12) Calculate the
indicated energy, actual energy and percentage error.
13) Plot the graph %
error verses load current.
Circuit Diagram
Observation Table
Sr. No.
|
IL
|
VL
|
Power
|
No. of
|
Time
|
Indicated
|
Actual
|
% error
|
|
Amps
|
Volts
|
watts
|
rotations
|
seconds
|
energy
|
energy
|
|||
1.
|
|||||||||
2
|
|||||||||
3
|
|||||||||
4
|
Calculations:
Wattmeter constant= (selected
voltage range*selected current range*p.f.)/ (full scale deflection)
Energy meter constant=______________ ws
Voltmeter reading VL = ______ Volts
Ammeter reading IL= _______ Amps
Wattmeter reading W=________
Watts
No. of rotations= 10
Time in Sec= ________
Indicated energy=Energy meter constant*No. of rotations=
_________ws
Actual energy=(Wattmeter reading *time)= _________ ws
% Errors=[(Ei-Ea)/Ei]*100=_________%
Hand Calculation:
Result:
The error is reduced after carrying out adjustment to
minimize the error from __________% to __________%.
Conclusion:
1.
Adjustments are separate for light load and top load.
2.
Calibrated energy meter will have very less or zero error in
its reading.
Questions
- State
various errors & adjustments in single phase energy meter.
- Explain
the working principle of single phase energy meter.
- Problems
on limiting error calculation.
Experiment No. 9
Object
Measurement
of strain produced by a force on the wires using Strain Gauge
Objectives
Measure
weight by using Strain gauge.
Theory
The strain gauge is the most common device for the electrical
measurement of static deformation. They rely on a proportional linear variance
of resistance (ΔR) due to variance in gauge length (ΔL) along its longitudinal
axis referred to as Gauge Facture (GF) and is typically no greater than 2. Gage
Factor is expressed in equation form as:
A strain gauge is made of a continuous electrical conductor
(bonded metallic or foil) called the grid, deposited on a very thin flexible
insulating material carrier figure 1.
GF = (ΔR/R)/ (ΔL/ L)
Figure.1
Typical gauge resistance (unstrained) is 120, 350, 600 and
700 ohms. But if attached to an object such as a metal beam, and if the beam is
under strain, that is, if a load is applied to the beam, the beam will deform
(bend, elongate or compress) carrying with it the gauge. We define Strain (ε)
as a deformation per unit length. Figure 2 shows a beam under load with
attached gauge. In this case, the top surface of the beam and the attached
gauge is in tension and has become elongate increasing the resistance of the
gauge.
Figure.2
Apparatus
S.No.
|
Apparatus
|
Range
|
Type
|
Quantity
|
1
|
Strain gauge kit
|
1
|
||
2
|
Connecting Wires
|
2.5sq.mm.
|
Copper
|
Few
|
Procedure
1)
Make connection of different wire to DPM.
2)
At zero weight DPM must show Zero.
3)
Put 1KG weight in pan and observe output of DPM if not make
by adjusting pot P3.
4)
Take reading of different weight like 1kg, 1.5kg, 1.7kg,
1.9kg observe DPM reading.
Observation Table
Sr.No.
|
Observed wt in Kg
|
Output of DPM in Kg
|
Calculation in Kg
|
Conclusion
Thus we measure
strain produced by a force on the wires using Strain Gauge.
Questions
1.
Describe instrumentation setup for measurement of temperature
using strain.
2.
What is strain gauge?
3.
What are the types of strain gauges?
Experiment No. 10
Object
To measure temperature using RTD (Resistance Temperature Detector).
Objectives
Measure temperature by using RTD.
Theory
Resistance temperature detector (RTD) is another temperature
sensing transducer which can be used to measure high temperatures’ basic
physical property of a metal is that its electrical resistivity changes with
temperature. All RTD's are based on this principle. The heart of the RTD is the
resistance element. RTD has a positive coefficient, i.e, when the temperature
of the RTD increases, its resistance also increases. Several varieties of
semi-supported wire-wound fully supported bifilar wound glass, and thin film
type elements.
Apparatus
Sr.No.
|
Apparatus
|
Range
|
Type
|
Quantity
|
1
|
RTD Kit
|
|||
2
|
Connecting Wires
|
2.5sq.mm.
|
Copper
|
Few
|
Procedure
1)
Keep switch SW2 in position marked “TEMP”.
2)
Connect a precision resistance of 100 ohm
3)
Adjust the pot P2 (MIN) to read 0.0 on DPM with pot P1(MAX)
in most clock wise position. This actions simulates ice bath temperature since
at 0 c PT 100 exhibits 100 ohm resistance.
4)
Now connect a precision resistance of 139 ohm across the
input terminals .Adjust pot P1 (MAX) to read 100.0 on DPM without disturbing
pot P1 (MIN).This action simulates boiling point temperature of water i.e. 100
c.
5)
Now connect RTD across input terminals and measure the
unknown temperature.
6)
Use heater and water bath to create temperatures higher than
the room temperature and tabulate the results in observation table .also note
the temperature of the hot water by using a mercury thermometer.
Precaution
1)
Handle the RTD carefully.
2)
Ensure that the RTD is not dropped on the flow.
Observation Table
Sr. No.
|
Temperature of Thermometer
|
Temperature of DPM
|
1
|
||
2
|
||
3
|
||
4
|
||
5
|
||
6
|
Conclusion
1)
RTD exhibits a linear
characteristic almost over the entire operating region.
2)
The temperature measurement with RTD falls in 2% accuracy.
Questions
1.
Explain the working of RTD.
2.
What are the applications of RTD?
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