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EXPERIMENT NO.1
((Temperature Measurements and Calibration))
Aim:
Measuring the temperature by different methods and draw the calibration curve with
thermometer readings.
1. Theory and procedure
1.1 Temperature measurement using liquid thermometers
In a glass thermometer, the relative expansion of a liquid compared to the content of the bulb is
measured. The majority of the liquid is in a spherical or cylindrical-shaped bulb that forms the
thermometers actual sensing element (1), the bulb opens into the long thin glass capillary tube
(2). Practically all liquids can be used in thermometers here a differentiation is made between
wetting (organic) and non-wetting liquids (mercury) wetting liquids cause additional errors as
the temperature drops, the organic liquids must be colored so that it is visible in the capillary
tube and the reading of the temperature made easier. Liquid containers for mercury are larger
than for other liquids due to the smaller coefficient of expansion.
Fig.1 Liquid thermometers
The volume of the medium in liquid thermometers changes in a accordance with the following
law:
Vt = V0 (1+‫ץ‬. ∆t) (1)
Vt = Volume at temperature t
V0 = Volume at 0ºC
‫ץ‬ = Coefficient of volume expansion in (1/k)
‫ץ‬ = for mercury approx. 0.17X103
(1/k)
∆t = Difference in temperature from 0⁰C in K

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Heat Transfer Laboratory
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1.2 Temperature measurement using Bimetallic thermometers
Bimetallic thermometers exploit the differential expansion of two different materials to
indicate the temperature, two or more layers of different materials are rolled to gather, during
the process different shapes can be manufactured depending on the application, one end of the
sensor is firmly anchored the other is coupled to a transmission gear or directly to a display
device. Contrary to rod type thermometers bimetallic sensors have only a low capacity to
perform work, they are thus practically limited to a usage for indicating equipment and are less
suitable for remote indication. Over wide measuring ranges the non-linear relationship of the
specific deflection to temperature becomes detrimentally apparent due to the relatively large
surface areas. Bimetallic thermometers that are exposed to the surrounding medium without
heavy protective housings react comparatively quickly [1-4]
.
The length of the individual metals changes in coordinate with the following formula:
Vt = V0 . (1+ α.∆t) (2)
Vt= Volume at temperature t
V0= Volume at 0ºC
α = Coefficient of liner expansion in (1/k)
∆t = Difference in temperature from 0⁰C in K
Fig. 2 Bimetallic thermometer
1.3 Temperature measurement using Gas thermometers
The thermodynamic temperature scale forms the theoretical basis of thermometry. As the scale
is very involved to reproduce, a number of fixed points are defined for use in the engineering
measurement filed, these are considerably easier to depict, the gas thermometer is one of the
most important devises used to relies the thermodynamic temperature scale over a very wide
temperature range almost down to absolute zero, using this method, the change in the pressure
or volume of a gas is measured as a function of temperature in accordance with the ideal gas
equation:
P.V = M.R.T (3)

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Heat Transfer Laboratory
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Here the mass (M) and the gas constant rare constant, all approximately ideal gases can be used
(helium, nitrogen, argon).
The lowest measurable temperature is just above the critical point of the respective charge gas
(nitrogen -147 ºC).
The following relationship exists between the gas states at two different temperatures:
P1.(V1/T1) = P2.(V2/T2) (4)
P= Pressure in N/mm2
V= Volume in m3
T= Temperature in K
Note 1: 0 ºC = 273 K
Note 2: always high degree scaled temperature glasses thermometer is filling mercury
Fig. 3 Gas thermometer
Table 1 Reading parameters
Reading
No.
Time
in
minute
Reference
temperature
⁰C
Liquid
thermometer
(non-organic)
Liquid
thermometer
(mercury)
Bimetallic
thermometer
Gas
thermometer
1 0
2 3
3 6
4 9
5 12
6 15
7 18
8 21
9 24

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Heat Transfer Laboratory
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Fig. 4 Temperature measurements and calibration apparatus [1]
2. Discussion questions
a) Why we get different reading between all the thermometers type?
b) Which thermometer is the best and has minimum reading error?
c) Why we have errors?
d) Discuss the (Temp.-Time) diagram that you draw it.
e) What do you suggest to get a better reading?
References
1. TecQuipment Ltd, The Temperature Measurement and Calibration apparatus, Model:
VDAS TD400.
2. Мохамед Б, Кароли Я, Зеленцов А.А. (2020) Трехмерное моделирование течения газа
во впускной системе автомобиля «формулы студент» Журнал Сибирского
федерального университета, 13(5); pp. 597-610. https://doi.org/10.17516/1999-494X-
0249.
3. Mohamad B., Karoly J., Zelentsov A.A. (2020) Hangtompító akusztikai tervezése hibrid
módszerrel, Multidiszciplináris Tudományok, 9(4), pp. 548-555.
https://doi.org/10.35925/j.multi.2019.4.58.
4. Yunus Cengel, Heat Transfer: A Practical Approach, 2nd
ed., McGraw-Hill Education –
Europe, 1997.
Barhm Abdullah Mohamad
Erbil Polytechnic University
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