This document discusses various temperature measuring instruments. It describes liquid-in-glass thermometers which measure temperature by the expansion and contraction of mercury in a glass tube. Bimetallic thermometers use the different coefficients of expansion of two bonded metals to indicate temperature. Pressure thermometers measure temperature by the pressure of a confined liquid or vapor. Pyrometers measure the intensity of infrared radiation emitted by an object to determine its temperature. The document provides details on the construction and working of these common temperature measurement devices.

1. GANDHINAGAR INSTITUTE OF
TECHNOLOGY
Mechanical Measurement and Metrology
Subject Code: 2141901
Topic: Temperature Measuring Instrument
Prepared By:-
130120119123- Panchal Yash
130120119126- Pandya Kartik
130120119139- Patel Harsh

2. INTRODUCTION
The accurate measurement of temperature is vital across
abroad spectrum of human activities,
 Including industrial processes (e.g. making steel)
Manufacturing;
 Monitoring (in food transport and storage),
 Health and safety.
 In fact, in almost every sector, temperature is one of the
key parameters to be measured

3.  The means of accurately measuring temperatures has long
fascinated people.
 One of the differences between temperature and other
physical concepts, such as mass or length, is that it is
subjective.
 Different people will have different perceptions of what is
hot and what is cold.
 To make objective measurements, we must use thermometer
in which some physical property of a substance changes
with temperature in a reliable and reproducible way.

4. SCALE
 Temperature is a measure of the thermal energy in the
body. Normally measured in degrees [°]using one of
the following scales.
1. Fahrenheit.[°F]
2. Celsius or centigrade. [°C]
3. Kelvin .[°K]

6. 1.Bulb: The reservoir for containing most of the
thermometric liquid (mercury).
2.Stem: The glass tube having a capillary bore
along which the liquid moves with
changes in temperature.
3. Scale: A narrow-temperature-range scale for
reading a reference temperature .
Construction
1.Liquid – in – Glass Thermometer

7.  The volume of mercury changes slightly with
temperature; the small change in volume drives the
narrow mercury column a relatively long way up the
tube.
 The space above the mercury may be filled
with nitrogen or it may be at less than atmospheric
pressure, a partial vacuum.

8. 2.BIMETALLIC THERMOMETER
 In an industry, there is always a need to measure and
monitor temperature of a particular spot, field or
locality.
 The industrial names given to such temperature
sensors are Temperature Indicators (TI) or
Temperature Gauges (TG).
 All these temperature gauges belong to the class of
instruments that are known as bimetallic sensors.

9. BIMETALLIC THERMOMETER
Two basic principles of operation is to be followed in
the case of a bimetallic sensor.
1) A metal tends to undergo a volumetric dimensional
change (expansion/contraction), according to the
change in temperature.
2) Different metals have different co-efficient of
temperatures. The rate of volumetric change depends
on this co-efficient of temperature.

10. Construction

11.  The device consists of a bimetallic strip of two different
metals .
 They are bonded together to form a spiral or a twisted helix.
 Both these metals are joined together at one end by either
welding or riveting.
 It is bonded so strong that there will not be any relative
motion between the two.
 The image of a bimetallic strip is shown below.

13. CONSTRUCTION
 A change in temperature causes the free end of the
strip to expand or contract due to the different
coefficients of expansion of the two metals.
 This movement is linear to the change in temperature
and the deflection of the free end can be read out by
attaching a pointer to it.
 This reading will indicate the value of temperature.
Bimetallic strips are available in different forms like
helix type, cantilever, spiral, and also flat type.

14. PRESSURE
THERMOMETER
1. Liquid Pressure Thermometers.
2. Vapour Pressure Thermometers.

15. 1.Liquid Pressure Thermometers.

16. VAPOUR PRESSURE THERMOMETERS.

17. PYROMETER
 A pyrometer is a device that is used for the temperature
measurement of an object.
 The device actually tracks and measures the amount of
heat that is radiated from an object.
 The thermal heat radiates from the object to the optical
system present inside the pyrometer.
 The optical system makes the thermal radiation into a
better focus and passes it to the detector.

18.  In an optical pyrometer, a brightness comparison is made
to measure the temperature.
 The device compares the brightness produced by the
radiation of the object whose temperature is to be
measured,
 For an object, its light intensity always depends on the
temperature of the object.
 After adjusting the temperature, the current passing
through it is measured using a multimeter, as its value
will be proportional to the temperature of the source when
calibrated.
 The working of an optical pyrometer is shown in the
figure below.

20.  As shown in the figure above, an optical pyrometer has
the following components.
1. An eye piece at the left side and an optical lens on the
right.
2. A reference lamp, which is powered with the help of a
battery.
3. A rheostat to change the current and hence the
brightness intensity.
4. So as to increase the temperature range which is to be
measured, an absorption screen is fitted between the
optical lens and the reference bulb.

21. Working
1.The radiation from the source is emitted and the
optical objective lens captures it.
2.The lens helps in focusing the thermal radiation on to the
reference bulb.
3.The observer watches the process through the eye piece
and corrects it in such a manner that the reference lamp
filament has a sharp focus and the filament is super-imposed
on the temperature source image.
4.The observer starts changing the rheostat values and the
current in the reference lamp changes.
5.This in turn, changes its intensity.
This change in current can be observed in three different ways.

22. The filament is dark. That is, cooler than the
temperature source.
Filament is bright. That is, hotter than the
temperature source.
Filament disappears. Thus, there is equal
brightness between the filament and temperature
source

23. At this time, the current that flows in the reference lamp
is measured, as its value is a measure of the temperature
of the radiated light in the temperature source, when
calibrated.

24.  Applications
1. Used to measure temperatures of liquid metals or
highly heated materials.
2. Can be used to measure furnace temperatures.

25. REFERENCES
 http://en.wikipedia.org/wiki/Temperature_mea
surement
 https://www.google.co.in/search?q=temperat
ure+measuring+instruments&espv=2&biw=1
366&bih=643&source=lnms&tbm=isch&sa=X
&ei=XEwhVaKMBs7_ugTS1oH4CA&sqi=2&v
ed=0CAYQ_AUoAQ

26. CONCLUSION
 From This Instruments we can measure
temperature of different objects..

27. Thank You