TECHNOLOGICAL UNIVERSITY OF THE PHILIPPINES

COLLEGE OF ENGINEERING
DEPARTMENT OF MECHANICAL ENGINEERING

EXPERIMENT IN

ME 5L
MECHANICAL ENGINEERING LABORATORY I

Submitted by:
Song, Stanley C.
BSME 4B

Submitted to:
Engr. Manuel Europeo

Experiment No. 5

CALIBRATION OF THERMOMETERS
Course Code: ME 5L
Course Title: Mechanical Engineering
Laboratory 1
Section: BSME 4B
Members: 1. Ramos, Franklin Silvester
2. Espeja, Ronald Castro
3. Mamangun, Harris
4. Song, Stanley
5. Carreon, Jephthah
1 Objectives
1
2
3

Date Performed: October 5, 2016

Date Submitted: October 12, 2016
Instructor: Engr. Manuel L. Europeo

To have the knowledge in thermometers.

To study and have ideas using different kinds of thermometers
To know the differences between the different types of thermometers.

2 Intended Learning Outcomes (ILO)

The students shall be able to:
1.1Identify the different types of thermometer.
1.2Discuss the information about temperature and providing proper
guidelines on operating the thermometers.
1.3Compare and discuss the differences in results given by different
thermometers

Discussions
Thermometers

A thermometer is
a
device
that
measures temperature or a temperature gradient. A
thermometer has two important elements: (1) a
temperature sensor (e.g. the bulb on a mercury-inglass thermometer) in which some physical change
occurs with temperature, and (2) some means of
converting this physical change into a numerical value
(e.g. the visible scale that is marked on a mercury-inglass thermometer).

Temperature
While an individual thermometer is able to measure
degrees of hotness, the readings on two thermometers
cannot be compared unless they conform to an agreed
scale. Today there is an absolute thermodynamic
temperature scale. Internationally agreed temperature
scales are designed to approximate this closely, based
on fixed points and interpolating thermometers. The
most recent official temperature scale is the
International Temperature Scale of 1990. It extends
from 0.65 K (272.5 C; 458.5 F) to approximately
1,358 K (1,085 C; 1,985 F).
Calibration
Thermometers can be calibrated either by comparing them with other
calibrated thermometers or by checking them against known fixed points on
the temperature scale. The best known of these fixed points are the melting
and boiling points of pure water. (Note that the boiling point of water varies
with pressure, so this must be controlled.)
The traditional method of putting a scale on a liquid-in-glass or liquid-in-metal
thermometer was in three stages:
1. Immerse the sensing portion in a stirred mixture of pure ice and water at
1 Standard atmosphere (101.325 kPa; 760.0 mmHg) and mark the point
indicated when it had come to thermal equilibrium.
2. Immerse the sensing portion in a steam bath at 1 Standard atmosphere
(101.325 kPa; 760.0 mmHg) and again mark the point indicated.
3. Divide the distance between these marks into equal portions according to
the temperature scale being used.
Other fixed points used in the past are the body temperature (of a healthy adult
male) which was originally used by Fahrenheit as his upper fixed point (96 F
(36 C) to be a number divisible by 12) and the lowest temperature given by a
mixture of salt and ice, which was originally the definition of 0 F (18 C).
(This is an example of a Frigorific mixture). As body temperature varies, the

Fahrenheit scale was later changed to use an upper fixed point of boiling water
at 212 F (100 C).
These have now been replaced by the defining points in the International
Temperature Scale of 1990, though in practice the melting point of water is
more commonly used than its triple point, the latter being more difficult to
manage and thus restricted to critical standard measurement. Nowadays
manufacturers will often use a thermostat bath or solid block where the
temperature is held constant relative to a calibrated thermometer. Other
thermometers to be calibrated are put into the same bath or block and allowed
to come to equilibrium, then the scale marked, or any deviation from the
instrument scale recorded. For many modern devices calibration will be stating
some value to be used in processing an electronic signal to convert it to a
temperature.
Precision, accuracy, and reproducibility
The precision or resolution of a thermometer is simply to what fraction of a
degree it is possible to make a reading. For high temperature work it may only
be possible to measure to the nearest 10 C or more. Clinical thermometers and
many electronic thermometers are usually readable to 0.1 C. Special
instruments can give readings to one thousandth of a degree. However, this
precision does not mean the reading is true or accurate, it only means that very
small changes can be observed.
A thermometer calibrated to a known fixed point is accurate (i.e. gives a true
reading) at that point. Most thermometers are originally calibrated to a
constant-volume gas thermometer. In between fixed calibration
points, interpolation is used, usually linear.] This may give significant
differences between different types of thermometer at points far away from the
fixed points. For example, the expansion of mercury in a glass thermometer is
slightly different from the change in resistance of a platinum resistance
thermometer, so these two will disagree slightly at around 50 C. There may be
other causes due to imperfections in the instrument, e.g. in a liquid-in-glass
thermometer if the capillary tube varies in diameter.
For many purposes reproducibility is important. That is, does the same
thermometer give the same reading for the same temperature (or do

replacement or multiple thermometers give the same reading)?

Reproducible temperature measurement means that comparisons are valid in
scientific experiments and industrial processes are consistent. Thus if the same
type of thermometer is calibrated in the same way its readings will be valid
even if it is slightly inaccurate compared to the absolute scale.
An example of a reference thermometer used to check others to industrial
standards would be a platinum resistance thermometer with a digital display to
0.1 C (its precision) which has been calibrated at 5 points against national
standards (18, 0, 40, 70, 100 C) and which is certified to an accuracy of
0.2 C.[35]
According to British Standards, correctly calibrated, used and maintained liquidin-glass thermometers can achieve a measurement uncertainty of 0.01 C in
the range 0 to 100 C, and a larger uncertainty outside this range: 0.05 C up
to 200 or down to 40 C, 0.2 C up to 450 or down to 80 C.
Uses
Thermometers utilize a range of physical effects to measure temperature.
Temperature sensors are used in a wide variety of scientific and engineering
applications, especially measurement systems. Temperature systems are
primarily either electrical or mechanical, occasionally inseparable from the
system which they control (as in the case of a mercury-in-glass thermometer).
Thermometers are used in roadways in cold weather climates to help determine
if icing conditions exist. Indoors, thermistors are used in climate control
systems such as air conditioners, freezers, heaters, refrigerators, and water
heaters. Galileo thermometers are used to measure indoor air temperature, due
to their limited measurement range.
Alcohol thermometers, infrared thermometers, mercury-in-glass
thermometers, recording thermometers, thermistors, and Six's thermometers
are used in meteorology andclimatology in various levels of
the atmosphere and oceans. Aircraft use thermometers and hygrometers to
determine if atmospheric icing conditions exist along their flight path. These
measurements are used to initialize weather forecast models. Thermometers
are used in roadways in cold weather climates to help determine if icing
conditions exist and indoors in climate control systems.

Cooking thermometers: Bi-metallic stemmed

thermometers, thermocouples, infrared thermometers, and thermistors are
handy during cooking in order to know if meat has been properly cooked.
Temperature of food is important because if it sits in environments with a
temperature between 5 and 57 C (41 and 135 F) for four hours or more,
bacteria can multiply leading to foodborne illnesses. Thermometers are used in
the production of candy.
Medical thermometers such as mercury-in-glass thermometers, infrared
thermometers, pill thermometers, and liquid crystal thermometers are used
in health care settings to determine if individuals have a fever or
are hypothermic.
Such liquid crystal thermometers (which use thermochromic liquid crystals) are
also used in mood rings and used to measure the temperature of water in fish
tanks.
Fiber Bragg grating temperature sensors are used in nuclear power facilities to
monitor reactor core temperatures and avoid the possibility of nuclear
meltdowns.
Types of thermometer

Mercury thermometer
The mercury-in-glass or mercury thermometer was
invented by physicist Daniel Gabriel Fahrenheit in
Amsterdam (1714). It consists of a bulb containing
mercury attached to a glass tube of narrow
diameter; the volume of mercury in the tube is
much less than the volume in the bulb. 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.

In order to calibrate the thermometer, the bulb is made to reach thermal

equilibrium with a temperature standard such as an ice/water mixture, and then
with another standard such as water/vapour, and the tube is divided into
regular intervals between the fixed points. In principle, thermometers made of
different material (e.g., coloured alcohol thermometers) might be expected to
give different intermediate readings due to different expansion properties; in
practice the substances used are chosen to have reasonably linear expansion
characteristics as a function of true thermodynamic temperature, and so give
similar results.
Physical properties
Mercury Thermometers cover a wide temperature range from -37 C (-34.6 F)
to 356 C (672.8 F), the instruments upper temperature range may be
extended though the introduction of an inert gas such as Nitrogen. This
introduction of an inert gas increases the pressure on the liquid Mercury and
therefore it's boiling point is increased, this in combination with replacing the
Pyrex Glass with Fused Quartz allows the upper temperature range to be
extended to 800 C (1472 F).
Mercury cannot be used below the temperature at which it becomes solid,
-38.83 C (-37.89 F). If the thermometer contains nitrogen, the gas may flow
down into the column when the mercury solidifies and be trapped there when
the temperature rises, making the thermometer unusable until returned to the
factory for reconditioning. To avoid this, some weather services require that all
mercury-in-glass thermometers be brought indoors when the temperature falls
to -37 C (-34.6 F).
To measure lower meteorological temperatures, a thermometer containing a
mercury-thallium alloy which does not solidify until the temperature drops to
-61.1 C (-78 F) may be used.
Phase-out
As of 2012, many mercury-in-glass thermometers are used in meteorology;
however, they are becoming increasingly rare for other uses, as many countries
banned them formedical use due to the toxicity of mercury. Some
manufacturers use galinstan, a liquid alloy of gallium, indium, and tin, as a
replacement for mercury.
The typical "fever thermometer" contains between 0.5 to 3 g (.3 to 1.7 dr) of
elemental mercury. Swallowing this amount of mercury would, it is said, pose
little danger but the inhaling of the vapour could lead to health problems.

Alcohol thermometer

The alcohol thermometer is an alternative to the mercury-in-glass

thermometer and has similar functions.
Unlike the mercury-in-glass
thermometer, the contents of an alcohol
thermometer are less toxic and will
evaporate away fairly quickly. An organic
liquid is contained in a glass bulb which
is connected to a capillary of the same
glass and the end is sealed with an expansion bulb. The space above the liquid
is a mixture of nitrogen and the vapor of the liquid. For the working
temperature range, the meniscus or interface between the liquid is within the
capillary. With increasing temperature, the volume of liquid expands and the
meniscus moves up the capillary. The position of the meniscus shows the
temperature against an inscribed scale.
The liquid used can be pure ethanol, toluene, kerosene or Isoamyl acetate,
depending on manufacturer and working temperature range. Since these
are transparent, the liquid is made more visible by the addition of a red or
blue dye. One half of the glass containing the capillary is usually enamelled
white or yellow to give a background for reading the scale.
The range of usefulness of the thermometer is set by the boiling point of the
liquid used. In the case of the ethanol-filled thermometer the upper limit for
measurement is 78 C (172 F), which makes it useful for measuring day and
night-time temperatures and to measure body temperature, although not for
anything much hotter than these. The ethanol version is the most widely used
due to the low cost and relatively low hazard posed by the liquid in case of
breakage.
Ethanol-filled thermometers are used in preference to mercury
for meteorological measurements of minimum temperatures and can be used
down to 70 C (-94 F).[1] The physical limitation of the ability of a
thermometer to measure low temperature is the freezing point of the liquid
used. Ethanol freezes at 114.9 C (174.82 F).
If an alcohol thermometer utilizes a combination of ethyl alcohol, toluene, and
pentane, its lower temperature range may be extended to measure
temperatures down to as low as 200 C (-328 F).[2] However, the

measurement temperature range c. 200 C to 78 C, is highly dependent

upon the type of alcohol used. The alcohol expands and contracts with the rise
and fall of a temperature.

Liquid crystal thermometer

A liquid crystal thermometer, temperature strip or plastic strip thermometer is a

type of thermometer that contains heat-sensitive (thermochromic) liquid
crystals in a plastic strip that change colour to indicate different temperatures.
Liquid crystals possess the mechanical properties of a liquid, but have the
optical properties of a single crystal. Temperature changes can affect the colour
of a liquid crystal, which makes them useful for temperature measurement. The
resolution of liquid crystal sensors is in the 0.1C range. Disposable liquid
crystal thermometers have been developed for home and medical use. For
example if the thermometer is black and it is put onto someone's forehead it
will change colour depending on the temperature of the person.
There are two stages in the liquid crystals:
-the hot nematic stage is the closest to the liquid phase where the molecules
are freely moving around and only partly ordered.
-the cold smectic stage is closest to a solid phase where the molecules align
themselves into tightly wound chiral matrixes.
Liquid crystal thermometers portray temperatures as colors and can be used to
follow temperature changes caused by heat flow. They can be used to observe
that heat flows by conduction, convection, and radiation.
In medical applications, liquid crystal thermometers may be used to read body
temperature by placing against the forehead. These are safer than a mercuryin-glass thermometer, and may be advantageous in some patients, but do not
always give an exact result,except the analytic liquid crystal thermometer
which show the exact temperature between 35.5 to 40.5 Celsius.
Liquid crystal thermometers are also commonly used in aquariums in
homebrewing, and in mood rings.
The Liquid crystal thermometer was invented by Bob Parker in California, one of
many of the inventor's thermochromic applications patented in the 1970s.

Bimetallic Thermometers

Bimetallic thermometers are made up of

bimetallic strips formed by joining two
different metals having different thermal
expansion coefficients. Basically, bimetallic
strip is a mechanical element which can
sense temperature and transform it into a
mechanical displacement. This mechanical
action from the bimetallic strip can be used
to activate a switching mechanism for
getting electronic output. Also it can be
attached to the pointer of a measuring
instrument or a position indicator. Various
techniques such as riveting, bolting, fastening can be used to bond two layers
of diverse metals in a bimetallic strip. However the most commonly used
method is welding. Since two metals are employed to construct a bimetallic
strip, hence they are named so.

Working
The working of a bimetallic strip
thermometer is based upon the fact
that two dissimilar metals behave in a
different manner when exposed to
temperature variations owing to their
different thermal expansion rates. One
layer of metal expands or contracts
more than the other layer of metal in a
bimetallic strip arrangement which
results in bending or curvature change
of the strip. The working principle of a
bimetallic thermometer is illustrated in
figure below. One end of a straight bimetallic strip is fixed in place. As the strip
is heated, the other end tends to curve away from the side that has the greater
coefficient of linear expansion.

Main Features

These types of thermometers work best

at higher temperatures, since their
accuracy and sensitivity tends to reduce
at low temperatures.

Bimetallic strip thermometers are

manufactured in various designs. One of
the most popular design i.e. flat spiral is
shown in the figure below. They can also
be wound into a single helix or multiple
helix form.

Bimetallic thermometers can be customized to work as recording

thermometers too by affixing a pen to the pointer. The pen is located in such
a way that it can make recordings on a circling chart.

Bimetallic strips often come in very long sizes. Hence, they are usually
coiled into spirals which make them compact and small in size. This also
improves the sensitivity of bimetallic strips towards little temperature
variations.

The bimetallic strip can be scaled up or down. On a large scale, it can

provide literally tones of force for mechanical control or other purposes. On
a smaller scale, it can provide the force and movement for micro machine
integrated circuits (MMIs).

Applications
Bimetallic strips are one of the oldest techniques to measure temperature. They
can be designed to work at quite high temperatures i.e. upto 500F or 260C.
Major application areas of a bimetallic strip thermometer include:
-For various household appliances such as ovens etc.
-Thermostat switches

-Wall thermometers
-Grills
-Circuit breakers for electrical heating devices
4. Materials

Stove

1L of

water

Mercury Thermometer
Thermometer

Alcohol

Bi-metal Thermometer
Stopwatch

Infrared
Thermometer
Strip Thermometer
5. Procedure
a)
b)
c)
d)
e)

Prepare the materials needed in the experiment.

Put 1 liter of water in the beaker.
Record the initial temperature of the water using the mercury thermometer.
Place the water in the heating pan.
Set the thermometers into the water, make sure that the thermometers were
placed firmly.
f) Start heating the water.
g) Record the time until the temperature in the mercury thermometer reaches
100C.
h) Record the temperatures given by the other thermometers.
i) Compute for Q.
6. Data and Results
Tap water Temperature = 28C = T1
Mercury Thermometer = 100C
Alcohol Thermometer = 100C

Bimettalic = 98C
Vapor Pressure Thermometer = 78C
Strip Thermometer = 88C
Infrared Thermometer = 100C
7. Documentation

8. Analysis and Data

Interpretation
We gathered the
temperature of water using different types of
thermometer in the conducted experiment. As the
mercury thermometer reached 100 degree Celsius,
the other thermometer displays different results
because it contains different composition from
each other and in the case of the alcohol
thermometer, they are calibrated differently but the difference is just a
small amount.
9. Observation
Data shows that the temperature readings are distinct from
different types of thermometer used. Given that Mercury, Alcohol, and
Infrared thermometers has 100C calibration, Bimettalic has 98C, Vapor

Pressure Thermometer was measured 78C, and Strip thermometer as

88C calibration. The given results expresses that thermometers have
calibrations having different characteristics.
10. Conclusion and Recommendation
In accordance to the conducted experiment the temperatures
measured in each thermometers are different from each other. Therefore,
these thermometers are structurally different with each other and are
made from different materials like the bi-metal thermometer which is
made up of bimetallic strips formed by joining two different metals having
different thermal expansion coefficients which show different results.
Each thermometer is made differently for different uses and where it is to
be used.