Experiment No1 [Calibration of Thermometers]

8/3/2019 Experiment No1 [Calibration of Thermometers]

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Experiment No. 1

Calibration of Thermometers

Date Performed: January 17, 2012Date Completed: January 17, 2012

Submitted by

Group No. 1

Group Leader: LO, Brian F.

Group Members:CO, Lizette Milaney P.

MANALO, Alyssa Mara C.MULINGTAPANG, Justinn Donn S.

EA2

Submitted to

Dr. Michael Angelo B. Promentilla

February 1, 2012


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I. Objectives

A. To familiarized with the different temperature measuring device, such as MercuryThermometer, Dial Thermometer and Thermocouple, in terms of how it works and howto properly use it.

B. To be knowledgeable in the calibration of these thermometers utilizing a block calibrator

and as well as using the physical properties of water specifically the temperature of iceand boiling temperature.

C. To be able to derive a calibration equation for thermocouple.

II. Theory / Literature Review

Temperature quantitatively indicates the degree of hotness or coldness of a certain body. Achange in temperature is directly proportional to that in kinetic energy since it brings about anincrease in movement and the frequency of intramolecular and intermolecular collisions. Tomeasure such property, different types of thermometers can be used. To name a few, theexpansion thermometer shows temperature changes when there is a change in volume;

electrical resistance thermometer, change in electrical resistance of the conductor;thermocouples, change in voltage; and optical pyrometer, change in luminosity or brightness.

The temperature in a thermometer is known through looking at the scale. The scale present is astandard and it is based on the change in the thermal energy content that is proportional to thechange in pressure of hydrogen at constant mass and volume. A reading can be made basedon two points, the reference point (or ice point), from which the reading is based and the secondstandard point (or steam point). The ice point is different from the freezing point. It is thetemperature where solid and liquid water may coexist in equilibrium. On the other hand, thesteam point is the temperature where pure water is boiling. Both the ice and steam point occurunder the standard atmospheric pressure.

According to the International Standards organization (ISO) has developed a number ofstandards specifically directed to calibration of measurement devices. Calibration entails theadjustment of measurement of a certain device to agree with the value from the standard.Moreover, specific calibration is only done for a certain device. In calibration of temperaturemeasuring device, the constant volume gas thermometer is an apparatus that measurestemperature upon variations in the pressure at constant volume. The hydrogen gas is the basisfor the standard and other important values of temperature.


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III. Setup

A. Actual Setup

B. Engineering Sketch

Steam Bath Setu Ice Bath Setu

Mercury

Thermometers and

Dial Thermometer

immersed in a heated

beaker with water Block Calibrator

Steam Bath Setup Ice Bath SetupMercury

Thermometers and

Dial Thermometer

immersed in a heated

beaker with water

Block Calibrator


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IV. Summary of Procedures

In calibrating temperature measuring devices, the behavior of mercury thermometers was first observed

through measuring the temperature of ice and the boiling point of water. With these physical properties

of water, three mercury thermometers and dial thermometer was also observed on the basis of

thermocouple. Lastly, thermocouple and one of the mercury thermometers was observed on the basis

of block calibrator.

As for the first part of the experiment, ice bath was prepared. The initial reading of each mercury

thermometer was first recorded before the thermometers were placed through the holes on top of the

ice bath and were lowered until the bulb is near the bottom. In this way, errors were prevented since

the surface temperature of the container somehow differs from ice temperature. At this setup,

temperature was recorded with time until it reaches a constant value. Errors from each temperature

were calculated by comparing to the theoretical ice temperature of zero degrees centigrade. These were

repeated for thermocouple and dial thermometers. For measuring the boiling point of water, a steam

bath was prepared. Same procedure was done on the ice bath except that the bulb of the mercury

temperature was not submerged in the water as it would automatically shoot the mercury up the

cylinder and explode. Each values recorded were also compared with the theoretical value of onehundred degrees centigrade. To graphically discern the behavior of the thermometers, a linear equation

was derived by plotting the temperature as a function of length. Moreover, through the percentage

errors calculated, the reliability of each instrument was compared.

This was followed by measuring the temperature of water using the three mercury thermometers, dial

thermometers and thermocouple simultaneously. The temperature for each instrument was, then,

recorded with every five degrees increment. As it reaches boiling point, the readings were then

recorded for every decrement of five degrees centigrade until it has reached room temperature. The

values recorded were tabulated and graphed for comparison. At the same time, errors with respect to

the value entered by the thermocouple were observed and graphed as a function of temperature. In

utilizing block calibrator, same method was used except that this time the thermometer andthermocouple is calibrated. With the values obtained, a calibration equation was derived for

thermocouple and was tested with the temperature provided by the block calibrator.

V. Data

Table 1. Temperature of Ice

29.8


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Table 2. Boiling Point of Water

Table 3. Total Mercury Thermometer Length

Table 4. Mercury Thermometer Scale Calibration


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Table 5. Comparison of Temperature Reading from the Three Mercury Thermometers and Dial

Thermometer with the Basis on Thermocouple (Heating in 0C)

Table 6. Comparison of Temperature Reading from the Three Mercury Thermometers and Dial

Thermometer with the Basis on Thermocouple (Cooling in 0C)


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Table 7. Block Calibrator Readings (0C)

VI. Results and Analysis

The behavior of three different thermometers were observed through its markings and and its

corresponding length. Table 3 shows the minimum and maximum possible readings provided by each

thermometer as well as its total length it covers. Through simple calculations, the following linear

equations were derived for each mercury thermometer by utilizing the values recorded in Table 3.

( )

( ) ( )

On the other hand, Table 4 shows the ice temperature and boiling point of water. Linear Equations were

also obtained; however, minute differences can be observed from its slope which could be due to minor

errors in measuring the length between the markings.

( ) ( )

( )

It can be seen that the three different thermometers have different calibrations or intervals for every

degree centigrade. These equations can be utilized in order to get accurate and precise readings byentering the length covered starting either from the measured ice temperature to the current reading or

from the lowest reading of the thermometer to the current reading. Also, it must be noted that all

equations are true only for these thermometers and must not be interchange or use for other

thermometers. To check the accuracy of thermometers in measuring temperature, percent errors,

which are tabulated below, were calculated through the given theoretical values.


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Table 8. Theoretical Values for Ice and Boiling Temperature

Table 9. Percent Error for Ice Temperature

Table 10. Percent Error for Boiling Temperature

With the given data above, minute deviations from the theoretical values were observed for measuring

ice temperature compared with boiling temperature values. The differences in errors for measuring

both physical properties of water also show the differences of calibrations of each thermometer. Some

errors could be induced as to how each instrument was positioned in the ice bath or steam bath since

heat transfer is a function of position. Among the instruments used, Thermometer 1 provides a more

accurate value basing on the theoretical values obtained. On the same basis, thermocouple provides the

least accuracy.

To provide a clearer view of deviations for each temperature measuring devices, Table 5 and 6 shows

the recorded temperature for heating and cooling water for the three mercury thermometers and dial

thermometer while having a basis on the temperature provided by the thermocouple. A parity chart was

developed for the four instruments as shown below.

0

20

40

60

80

100

120

0 5 10 15 20

Thermometer 1 (0C)

Cooling

Heating


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0

20

40

60

80

100

120

0 5 10 15 20

Thermometer 2 (0C)

Cooling

Heating

0

20

40

60

80

100

120

0 5 10 15 20

Thermometer 3 (0C)

Cooling

Heating

0

20

40

60

80

100

120

0 5 10 15 20

Dial Thermometer (0C)

Cooling

Heating


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Thermometer 1 and 2 almost achieved consistency in measuring heating and cooling temperatures.

Thermometer 3 has one value deviated from its trend which evidently has made mistake in recording

the temperature. On the other hand, dial thermometer changed in recording temperatures but it did not

deviate significant differences. Moreover, using the plotted values of the temperature recorded in

heating water, it can be said that Dial Thermometer has the closest value with respect to the readings of

thermocouple. However, this does not say that Dial thermometer has the most accuracy due to the fact

that thermocouple could have temperatures dissimilar with the standard measurement of the blockcalibrator. Percent errors were compared and determined with the temperature values of

thermocouple. These were graphed with temperature as shown below to magnify the errors induced for

every measurement recorded.

0

20

40

60

80

100

120

0 5 10 15 20

Comparison of Temperature Reading (Heating 0C)

ThermocoupleMercury Thermometer 1

Mercury Thermometer 2

Mercury Thermometer 3

Dial Thermometer

Linear (Thermocouple)

Linear (Mercury Thermometer 1)

Poly. (Mercury Thermometer 2)

Poly. (Mercury Thermometer 3)

Poly. (Dial Thermometer)

0.00

5.00

10.00

15.00

20.00

25.00

0 50 100 150

%

Error

Temperature

Thermometer 1 (0C)

0.00

5.00

10.00

15.00

20.00

0 50 100 150

%

Error

Temperature

Thermometer 2 (0C)


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From the graphs obtained, all instruments starting from the reading of a room temperature produce

smaller error as temperature increases.

In using a block calibrator, both thermometer 2 and thermocouple were compared by the graph below.

At the same time percent error was recorded with reference to the block calibrator. These were plotted

against temperature with the same purpose of observing the trend of error for every temperature

measurement.

0.00

5.00

10.00

15.00

20.00

0 50 100 150

%E

rror

Temperature

Thermometer 3 (0C)

0.00

5.00

10.00

15.00

20.00

25.00

0 50 100 150

%E

rror

Temperature

Dial Thermometer (0C)

0

20

40

60

80

100

120

140

160

180

0 5 10 15

Comparison of Temperature Reading

(Heating 0C)

Thermocouple

Mercury Thermometer

2

Block Calibrator

Linear (Thermocouple)

Linear (Mercury

Thermometer 2)

Linear (Block

Calibrator)


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Both readings from thermometer 2 and thermocouple are near to the values presented by the block

calibrator. Thermocouple also shows a decrease in error as temperature rises. Moreover, thermometer

2 with notable small errors within the range of zero to two percent varies but somehow follows the

increasing trend of error with every increase of temperature. A calibration equation was derived forthermocouple as shown which could be used to calibrate other instruments tested for this experiment.

The equation derived is not that perfect or suitable graph for calibration. However, with equal to

0.9757, it can somehow make the calibration for thermocouple almost reach the same temperature

reading with the block calibrator.

Testing this equation with sample points obtained and having x as the current temperature, error could

still be depicted but much smaller compared with the previous reading.

VII. Observations

A. Both steam bath and ice bath are open systems due to the presence of holes at the topmost

part of the container. This might incur small errors as open system could not be in equilibrium.

B. Upon subjection of the thermometer to the steam bath, and regardless of the thermometer

used, the temperature approached quickly than on the ice bath.

C. It takes time to calibrate using block calibrator.

D. Different thermometer has different calibrations.

E. The thermocouple instantly reads the fixed temperature. However, it is the most unprecise

temperature measuring device as it only gives whole number values.F. Although the thermometers registered different values of temperatures, the temperature

change upon heating and cooling of the bath is almost the same for all thermometers.

0.00

0.50

1.00

1.50

2.00

2.50

0 50 100 150 200

%Er

ror

Temperature

Thermometer 2 (0C)y = -4E-10x6 + 3E-07x5 - 7E-05x4

+ 0.0088x3 - 0.6175x2 + 22.305x -

313.57

R = 0.9757

0.00

2.00

4.00

6.00

8.00

10.00

0 50 100 150 200

%Er

ror

Temperature

Thermocouple (0C)


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VIII. Conclusion and Recommendations

The researchers were able to compare the usage of each temperature as well as the variations in the

temperature values. It was also observed that a more precise way of determining the temperature for

mercury thermometers is by utilizing temperature as a function of length. Using the block calibrator as

the basis for calibration, an equation can be derived to make readings as accurate and precise as

possible.

Using the analysis of percent error, it can be observed that the whole experiment manage to control an

error range of zero to fifteen percent. It can also be said that the experiment did not manage to obtain

accurate and suitable calibration equation for thermocouple and linear equations with temperature as a

function of length for mercury thermometers. However, the group was able to operate such equations

in which small errors would be met. Also, the researchers were able to know and use other temperature

measuring devices such as thermocouple and dial thermometer. This paper also helped the group in

making a calibration equation.

It was also observed and concluded that making use of calibration equation for a specific temperature

measuring device is very important especially to operating industries as small change in the wantedtemperature could lead to damage or disruption to some operations. To minimize the occurrence of

errors in dealing with calibration, it is further recommended that more trials would be performed and

that the researchers must be very careful, accurate and precise in recording data to alleviate source of

error.

IX. Answers to Guide Questions

1.] What are the various units used in temperature measurements? State their origin and the equations

to convert one to the other.

Celsius (0

C)It is named after the Swedish Astronomer, Anders Celsius. It was also known as centigrade

from the latin centum which means 100 and gradus translated as steps. This is based on

the freezing and boiling temperature of water.

Fahrenheit (0F)

It was invented by Daniel Gabriel Fahrenheit who was the German physicist. Fahrenhait scale

is divided into 180 degrees.

Rankine (0R)

It is the absolute scale, which corresponds to Fahrenheit degree units. It is named after W. J.

M. Rankine, a Scottish engineer.

Kelvin (K)

It is the absolute scale, based on degree units the size of those in the Celsius scale, which is

named in honor of William Thomson also known as Lord Kelvin.

The following equations are used to convert each temperature measurements:


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2.] What is the property of mercury which makes it an ideal medium for liquid-in-glass thermometer?

Like mercury, volume of liquids automatically and uniformly response to the increase and decrease

of temperature. It also has a high boiling point and a low melting point thus making it liquid at room

temperature.

3.] Describe the principle of a thermocouple. Give at least five types of thermocouples not mentioned in

the discussion. How are they classified? Specify the temperature range and limitations of each type.

Temperature measurement using thermocouples are based on an electric current that flows in a

continuous circuit of two different metallic wires if the two junctions are at different temperatures.

They are classified into the type of metal used.

Type Wires Temperature

Range

Type N Nicrosil-Nisil 0-1300

Type R Platinum-Rhodium 125-1768

Type S90% Platinum 10% Rhodium-

Platinum150-1768

Type CTungsten 5% Rhenium-

Tungsten 26% Rhenium0-2320

Type M

20% Nickel Alloy18%

Molybdenum-19% Nickel Alloy

0.8% Cobalt

0-1400

4.] Explain the reason why temperature of the vapor is measured just above the surface of the liquid.

The bulb or the mercury inside the thermometer is very sensitive to a change in temperature. Heat

transfer at liquid phase is higher compared at gaseous state; thus, when submerged to a liquid, the

volume of mercury will increase aggressively which has a tendency to explode. It must, then, be

placed above the surface of the liquid where steam, which is at equal temperature as water at liquid

phase during boiling point, can be measured directly without any occurrence error.

5.] Describe at least four modern instruments to measure temperature.

Bimetal Thermometers

Thermostatic bimetal can be defined as a composite material made up of strips of two or

more metals fastened together. This composite tends to change curvature when subjected to

a change in temperature. With one end of a straight strip fixed, the other end deflects in

proportion to the temperature change, the square of the length, and inversely as the

thickness, throughout the linear portion of the deflection characteristic curve.

Infrared Temperature Measurement Device

It uses Infrared sensors which are non-contacting devices. They infer temperature by

measuring the thermal radiation emitted by a material. Total Radiation Pyrometers

The thermal radiation is detected over a large range of wavelengths from the object at high

temperature. The detector is usually a thermopile which is built by connecting several

thermocouples in series to increase the temperature measurement range.

Disappearing Filament Pyrometers

It can be classified as spectral pyrometers. The brightness of a lamp filament is changed by

adjusting the lamp current until the filament disappears against the background of the target


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at which point the temperature is measured. Because the detector id the human eye, it is

difficult to calibrate for online measurements.


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Appendix

I. Sample Calculations

(From Table 5, Thermometer 1, first reading):

| |

(Calibration Equation):

*By substituting the current reading to x the calibrated reading is obtained

() () () () ()

()

Block

CalibratorThermocouple

Calibrated

Reading

51 47 54.26

61 56 64.92

II. References

[1] Padolina, M. C. et. al. (2004). Conceptual and functional chemistry modular approach. Quezon City:

Vibal Publishing House, Inc.

[2] Chang, R. (2010). Chemistry tenth edition. New York: McGraw-Hill Companies, Inc.

[3] Smith, J. M. et. al. (2005). Introduction to chemical engineering thermodynamics seventh edition.

New York: McGraw-Hill.

[4] Himmelblau, D. & Riggs, J. (2005). Principles of chemical engineering seventh edition. Singapore:Pearson Education South Asia Pte Ltd.

[5] Green, D. & Perry, R. (2008). Perrys chemical engineers handbook eighth edition. China: McGraw-

Hill Companies, Inc.

[6] http://inventors.about.com/od/tstartinventions/a/History-Of-The-Thermometer.htm

[7] http://www.scienceclarified.com/everyday/Real-Life-Physics-Vol-2/Thermal-Expansion-Real-life-

applications.html#b


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III. Self Evaluation Report

Student NameRole

(Leader/Member)Evaluator

Score

(100)Remark

CO, Lizette Milaney P. Member LO, Brian F. 100

She makes sure

that everything isdone as accurate

as possible.

MANALO, Alyssa Mara C. Member LO, Brian F. 100

She performs well

on every part of

experiment and

takes note on how

the values were

obtained.

MULINGTAPANG, Justinn

Donn S.Member LO, Brian F. 100

He critically thinks

of ways on how

and why it

happens.

LO, Brian F. Leader

CO, Lizette

Milaney P.100

He took the

initiative to be the

first experiment's

leader. He also put

together and

organized the

experimental data.

MANALO, Alyssa

Mara C.100

equally distributed

tasks among

members

MULINGTAPANG,

Justinn Donn S.100

Makes sure thatevery step of the

experiment is

done. Does not

leave anything

undone. Hence,

the experiment is

finished in one go.

Documents

Experiment No1 [Calibration of Thermometers]