TITLE:

MEASUREMENT OF TEMPERATURE USING DIFFERENT TYPES OF

THERMOMETER
OBJECTIVE

 To compare the efficiency, response time and sensitivity of various

thermometers

APPARATUS REQUIRED

 Various laboratory thermometers

 A temperature measuring apparatus with all necessary accessories
 Heating system
 Cooling system

THEORY
Temperature is simply the measure of hotness or coldness of a body. It
indicates the direction in which heat energy spontaneously flows i.e from a
hotter to a colder one. And, a device/sensor which measures is called a
thermocouple.It consists of two different types of metals, joined together at
one end. When the junction of the two metals is heated or cooled, a volatge is
created that can be coorelated back to the temperature. This phenomenon is
widely known as “seebeck effect”.
The amount of voltage depends upon the amount of temperature change and
the characteristics of the metals.
Thermocouples have a very wide temperature range i.e about -200 oC to
2500oC. They are durable, have a fast response time and have good
reproducibility. Because if these reasons, they are majorly used in science and
industry; applications including temperature measurement for kilns, gas
turbine exhaust, diesel engines, and other industrial processes. Its major
 secback is that accuracy and system errors of less than 1oC can be difficult to
achieve.

A thermometer is also a device which measure temperature. It can simple be

used to measure temperature of various solid,liquid and gases. There are 3
most commonly used units of measurement for temperature which are
Celsius, Fahrenheit and Kelvin. Thermometer consisting of mercury which is
contained in a bulb at the bottom of a graduated sealed glass capillary tube
marked in degree Celsius or Fahrenheit is referred as a mercury thermometer.
With changes in temerpature, The mercury correspondingly contracts or
expands and the temperature reading can be observed in the calibartion of the
wall of the thermometer. Mercury thermometer is specifically used in this
experiment because its has a high boiling point i.e 356oC.
Mercury is highly sensitive, responds quickly with change in temperature,
durable and lost lasting making it suitable for laboartory. It cannot be used in
very cold places since, it freezing point is just -37oC. Its major demerit is it’s
poisonous nature. It is highly toxic for living beings and thus should be handled
with care.

The platinum resistance thermometer is a type of thermometer which uses

platinum for determing the
temperature. It works on the principle that the resistance of the platinum changes
with change in
temperature. This thermometer measure the temperature over the range of
200oC to 1200oC. The
platinum is an unreactive metal and can be easily drawn into fine wires. Because
of these properties, it
is used as a sensing element in thermometer. The resistance of platinum changes
linearly with
temperature and due to this reason it is used for measuring temperature. The
resistance of platinum is
measured by passing AC or DC through it. Because of the current, The voltage
induces across the metal
which is measured with the help of a voltmeter. The reading of voltmeter is
converted into temperature
with the help of the calibration equation.
Temperature measurement is comparatively easier in this thermometer than
others. It is quite sensitive
and gives off precise reading of temperature. But it has a bit of a slow response
and it major
disadvantage is that even though its melting point is 1800 oC, as the temperature
exceeds 1200oC it
starts evaporationg.

PROCEDURE

In this experiment, due to the inavailability and difficulty of maintaining the

cold system, we only conducted the experiment using the hot system which in
our case we used hot boiling water that was heated with the help of a electric
heating jug. As the water boiled from 0oC to potentially 100oC, we measured
the temperature change using the thermocouple and thermometers in the
interval of 5 seconds until concurrent reading was procured and the
corresponding graphs were plotted. Then finally the result of these different
measuring devices was compared to conclude which one is more sensitive.

OBSERVATIONS

Observation Table of reading of Platinum thermometer:

Temperature (°C) Time (sec)

50.1 0
 62.8 5
70.4 10
76.1 15
81.2 20
85.3 25
88.4 30
90.6 35
92.2 40
93.5 45
94.5 50
95.2 55
95.9 60
96.4 65
96.7 70
96.9 75
97.1 80
97.2 85
97.4 90
97.5 95
97.5 100
97.6 105
97.6 110
97.6 115

Observation table of reading of Thermocouple thermometer:

Temperature(°C) Time(sec)
73 0
86 5
92 10
94 15
96 20
97 25
97 30
97 35
 97 40
Observation table of mercury thermometer:

Temperature (°C) Time(sec)

95 0
96 5
96 10
96 15
96 20
96 25
96 30

CALCULATIONS

Calculations of platinum thermometer:

Temperature
120

100 f(x) = 0.289026086956522 x + 72.8143333333333

f(x) = 11.424481295639 ln(x) + 47.1225936401202

80

60

40

20

0
0 20 40 60 80 100 120 140

From above graph,

Slope=Sensitivity= dy/dx = 0.289

Calculations of Thermocouple Thermometer:

Temperature
96.2
f(x) = 0.0214285714285714 x + 95.5357142857143
96
95.8
95.6
95.4
95.2
95
94.8
94.6
94.4
0 5 10 15 20 25 30 35

From above graph,

Slope=Sensitivity= dy/dx= 0.4733

Calculations of Mercury thermometer:

Temperature
96.2
f(x) = 0.0214285714285714 x + 95.5357142857143
96
95.8
95.6
95.4
95.2
95
94.8
94.6
94.4
0 5 10 15 20 25 30 35

From the above graph,

Slope=Sensistivity= dy/dx=0.0214

RESULT AND CONCLUSION

From the above observations and calculations, it was found that
Sensitivity of platinum thermometer =0.289
Sensitivity of Thermocouple thermometer=0.4733
Sensitivity of Mercury Thermometer= 0.0214
Hence, we can conclude that, Thermocouple thermometer was comparatively
more sensitive than the other temperature measuring devices we had at
disposal.
 SOURCES OF ERROR

 If the graduation of an instrument is not accurate it can lead to systematic

errors.
 If the observer’s eye is not at the correct angle then it can lead to parallax
error.
 There can be measurements errors if thermal expansion is not accurately
compensated.
 External factors like ambient temperature,humidity and air pressure can
influence the accuracy of the temperature measurement.
 Rounding error can occur is the actual value falls between two readings
expecially in case digital instruments.
 Observer bias or misinterpretation of readings can introduce errors, especially
while using analog instruments.

PRECAUTIONS

 The instruments should be regularly calibrated to ensure the instrument’s

measurements are accurate and reliable.
 Readings of analog instruments should be taken by looking directly in front of
of the scale to avoid parallax error.
 Instruments with an appropriate level of measurement resolution should be
selected to prevent rounding errors.
 The instruments should be handled with care to avoid physical damage or
misalignment that could lead to errors.