MESB333 - ENGINEERING MEASUREMENT AND LAB

EXP3–TEMPERATURE MEASUREMENT

SEMESTER 1, 2014/2015

SECTION 02B

GROUP 05

GROUP MEMBERS ID

MANIMUGILAN SUBRAMANIAM ME090187

MOGANA THEEBAN KARUNAKARAN ME090188

JEEVA RAJAKUMARAN ME090162

JEGANRAJ RAVINTHARAN ME090164

JAYASHARMAN SUBRAMANIAM ME090161

ALREWAISHED AHMED ABDULSALAM ME089687

AUTHOR:

MANIMUGILAN SUBRAMANIAM (ME090187)

LAB INSTRUCTOR:DR.SHAHIDA BEGUM

1

SUMMARY AND ABSTRACT

Experiment 3- Temperature measurement

This experiment consists of 3 parts:

Part 1 – Time constant

This experiment is regarding measuring temperature using different kind of measuring devices

such as resistance thermometer , thermistor ,The Vapor Pressure Manometer, The Bi-Metal

Thermometer .Results obtained from this devices are compared with mercury thermometer. As

time increases, temperature also increases. After a certain amount of time, the temperature

becomes constant.

Part 2 - Temperature Measurement Using Type K thermocouple

Purpose of this experiment is to investigate relation between voltage output and temperature.

Experiment is conducted using Thermocouple and Thermistors. The summary of the experiment

is as the temperature increases, the voltage also increases.

Part 3 – Humidity

In this experiment humidity also one of the factor that changes the result of this experiment.

When the thermometer bulb is dry, the humidity reading is high. When the thermometer bulb is

wet, the humidity reading is low.

2

EXPERIMENT 1: TIME CONSTANT

OBJECTIVE

To study the relational the time constant of different type of temperature measuring

devices with reference to mercury filled thermometer.

To comprehendthe concept of resistance thermometer (or RTD) and thermistor using the

PT100 and NTC probes

To understand the relationship between resistance and temperature, and main difference

between resistance thermometer and thermistor.

THEORY

Temperature is a measure of hotness. Together with a measure of ‘thermal mass’ of a body it

gives an indication of the total thermodynamics energy that body contains. There are many

scales for the comparison of temperatures, the most important is with their corresponding values

for melting ice and boiling water (which are common reference temperatures) being given in the

table below.

Scale Melting Ice Boiling Water

Celsius(or Centigrade) 0 0C 100

0C

Fahrenheit 32 0F 212

0F

Kelvin (Absolute Scale) 273 K 373 K

In this experiment you will be familiarized with the following temperature measurement

devices:

a) Resistance thermometer (TYPE K)

b) Thermistor (NTC)

3

The Liquid Filled Thermometer

This type of thermometer depends on the expansion of a liquid associated with an increase in

temperature. The most common type is the mercury-in-glass thermo meter. This thermometer

consists of a capillary tube with a bulbous end. On heating, the mercury expands relative to the

glass container and a column is pushed along the bore of the tube. A scale along the tube,

calibrated in units of temperature, gives a direct reading of temperature. The mercury-in-glass

thermometer is an accurate device but is very fragile and care should be exercised in use. The

mercury may be replaced by other fluids according to the application. For example, alcohol is

cheaper and may be used at lower temperatures than mercury. A mercury-in-glass thermometer

is supplied with the Temperature Measurement Bench due to its stable and accurate performance.

For accurate measurement of temperature using a liquid filled thermo meter, it is important that

the thermometer is immersed into the medium being measured by the correct amount. The depth

of immersion is usually stated on the stem of the thermo meter and defines the condition under

which calibration is maintained. The immersion depth may be partial or total and is independent

of filling or range.

The Vapor Pressure Manometer

This consists of a metal bulb partially filled with fluid, which is connected to the sensing element

of a Bourdon gauge. The space above the fluid is filled with vapor of the fluid, the pressure of

which is display on the Bourdon gauge. The gauge is calibrated directly in units of temperature

corresponding to the equivalent, pressure of the vapor but calibration is far from linear due to the

pressure increasing more and more rapidly as the temperature increases. For this reason, the

vapor pressure thermometer is suitable only for operation over short ranges of temperature and

suffers from lack of sensitivity at low readings. In service, the range should be selected so that

the gauge remains within operational limits with the normal operating point at approximately

two thirds of fullscale reading. Vapor pressure thermometers offer the advantage of remote

reading. The thermometer may be ordered with a metal capillary tube connecting the bulb to the

gauge, permitting remote operation over distances up to sixty meters. Correct orientation of the

bulb and gauge should be preserved f or ac- curate results.

The Bi-Metal Thermometer

Expansion of solids may be used to measure temperature but direct measurement is impractical

due to the very small movements involved. However, if two thin metal strips, having different

coefficients of linear expression, are mechanically fastened together, the result is a strip which

bends significantly when heated. This combination is called a Bi-metal strip and the sensitivity

may be increased by coiling the strip into a spiral. One end of the strip is fixed to the case and a

pointer is attached to the other end. Linear scale may be obtained by suitable choice of metals.

This type of thermometer is very robust and has many applications throughout industry where

accuracy of measurement is not important.The bi- metal thermometer supplied with the bench is

mounted on the back-board and gives a direct reading of ambient air temperature.

4

Resistance Thermometer

The resistance of a material changes with temperature. Resistance thermometer uses this

relationship in measuring the temperature. If high accuracy is required, the material used in

resistance thermometer is platinum. Nickel is used in general operation and monitoring. Copper

is also suitable but only in a restricted temperature range of approximately 250, because copper

tends to corrode more severely when subjected to oxidation. Figure 3.1 shows the resistance

change of the metals as a function of the temperature T. They have a positive temperature

coefficient α. For the purpose of comparison a resistance characteristic of a thermistor (NTC)

was added, which runs much more non-linearly, and in contrast to the metals, demonstrates a

negative coefficient β.For small temperature ranges we may assume that linear relationships exist

between resistance and temperature. From figure 3.2 one can deduce the temperature-dependent

resistance ratio R (T) caused by the resistance change R is:

𝑅(𝑇) = 𝑅𝑜 + ∆𝑅 (1)

The rise of this function is 𝑚 = ∆𝑅/ ∆𝑇. ∆𝑅 = 𝑀∆𝑇 (2)

𝑅 𝑇 = 𝑅𝑜 + 𝑅 𝑅 (𝑇) = 𝑅𝑜 + 𝑚 𝑇

= 𝑅𝑜 (1 + 𝑚/𝑅𝑜∆ 𝑇)

= 𝑅𝑜 1 +

∆𝑅

𝑅𝑜

∆𝑇 ∆𝑇 (3)

Figure 3.1

From Figure 3.1 we can see that for large measurement ranges no linear relationship between

resistance R and temperature T can be assumed. In this case we must take into consideration,

apart from the linear temperature coefficient α1 , also the square temperature coefficients α2, and

for very large temperature changes ∆T also the cubic temperature coefficients α3, and if

necessary the biquadratic value α4.

𝑅 𝑇 = 𝑅𝑂(𝛼𝑂∆𝑇𝑂 + 𝛼1∆𝑇

1 + 𝛼2∆𝑇2 + … . .𝛼𝑛∆𝑇

𝑛) (4)

5

Thermal Response

The thermal response of a thermo meter to changes in temperature is probably the most

important characteristic to consider when selecting instrument at ion f or a particular application.

A thermo meter may be extremely accurate and stable in performance but totally unsuitable f or

use in a dynamic situation, due to a time lag between system temperature and thermometer

reading. The diagram below shows typical response curves for a thermometer when step changes

in temperature are applied. The response of the thermo meter is defined by the time ta ken f or

the temperature reading to change by 63.2% of the step change. For any thermometer, this time

will be a constant value irrespective of step change and is defined as the "time constant" f or the

thermometer. The time constant and response profile f or a thermometer will change if the

system is modified. For example, the speed of response of a thermometer will be slowed down if

it is protected from the system being measured by a thermo meter. The response will also be

affected by the thermal contact between the thermometer and pocket, fluid filling of the pocket

resulting in a reduction in time constant.

Figure 3.2

6

APPARATUS

A = Type K thermocouple O = Thermistor temperature meter

B = Pt-100 thermocouple P =Mercury filled thermometer

C = mV meter Q = Spirit filled thermometer

D = Mains switch 240VAC

E = EL CB/ MCB

F = Heater switch

G = Blower switch and speed controller

H = Pt-100 temperature meter

I = Type K temperature meter

J = Bi-metallic thermometer

K =Vapor compression thermometer

L = Vacuum flask

M =Hot water pot

N =Whirling psychrometer

7

PROCEDURE

1. The 3 pin plug was plugged to 220VAC main power supply. The power supply was

switched ON.

2. The MCB/ELCB was switched ON.

3. The main power supply for the apparatus was switch ON.

4. Water was poured into the hot water pot. The water level must at least half of the pot.

5. The small cap (on top the hot water pot) was removed from the hot water pot.

6. The desirable temperature measuring device was chosen and place it into the hot water

pot. Mercury Filled Thermometer will be the reference temperature point.

7. The initial temperature reading was state down and recorded it into the table.

8. The water heater turned ON (ensure the hot water pot is turn ON as well).

9. For every 2 minute interval, the temperature reading was recorded into the table.

10. Step 9 is repeated until the water boil.

Repeat the experiment with different type of temperature measuring devices

Note: To discharge the hot water from the pot, request assistant from lab technician

DATA AND RESULTS

Temperature (̊C)

Time (min) Mecury

Type

Bi-

Metallic

Digital Pt 100 Type K Vapour Pressure

0 26 28 24.9 25.5 21.5 31

2 28 30 31.5 26.0 24.5 31

4 37 32 37.6 31.8 32.2 34

6 50 38 50.1 42.8 44.1 42

8 64 50 62.1 55.7 58.9 55

10 78 62.5 78.7 69.8 73.0 70

12 91 80 91.8 85.8 87.3 86

14 102 98 99.9 99.6 99.4 104

Table1. Temperature measurements result

8

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against Time for Mercury Type

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against Time for Bi-Metallic

9

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against Time for Digital

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against Time for Pt 100

10

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against Time for Type K

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against time for Vapor Pressure

11

Sample Calculation:-

For Mercury Type

Time constant = Temperature maximum x 0.632

= 102 x 0.632

= 64.464 C @ 8.2 min

For Bi-Metallic

Time constant = Temperature maximum x 0.632

= 98 x 0.632

= 61.936 C @ 9.82 min

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against Time for Mercury Type

12

For Bi-Metallic

Time constant = Temperature maximum x 0.632

= 99.9 x 0.632

= 63.1368 C @ 7.83 min

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against Time for Bi-Metallic

Y-Values

13

For Pt-100

Time constant = Temperature maximum x 0.632

= 99.6 x 0.632

= 62.95 C @ 9.15 min

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against Time for Digital

14

For Type K

Time constant = Temperature maximum x 0.632

= 99.4 x 0.632

= 62.82 C @ 8.61 min

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against Time for Pt 100

15

For Vapor Pressure

Time constant = Temperature maximum x 0.632

= 104 x 0.632

= 65.728 C @ 9.21 min

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against Time for Type K

16

DISCUSSION

1. Based on the graphs above, it is clear that temperature reading increases when the

time increases. This is because when the time increases, the temperature of water

increases. Once the temperature reaches the boiling point of water, the temperature

will get constant while the time keep increasing. It remains constant because that’s

the boiling point of water and water will be evaporated into steam after this

temperature.

2. Based on the time constant calculation of each type of temperature measurement

device, thermistor has the smallest time constant.

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16

Graph of Temperature against Time for Vapor Pressure

17

CONCLUSION

Finally , we knew how to measure temperature using different measuring devices

alike resistance thermometer , thermistor ,The Vapor Pressure Manometer, The Bi-Metal

Thermometer. We found out that As time increases, temperature also increases.After a

certain amount of time, the temperature becomes constant. We also learned the concept

of resistance thermometer (RTD) and thermistorsPT 100 and PTC probes. The PTC

probes perform a negative coefficient of temperature; which means the voltage will

decrease when temperature increases and it is highly sensitivite. This is due to the

behavior of semiconductor as material of PTC probes. For this experiment, we conclude

that the PTC probe have higher sensitivity then PT 100 Resistance Thermometer.

Therefore, it is suitable to use PT 100 for household and outing temperature

measurement, whereas, the PTC probe is usually used for highly sensitive temperature

measurement, such as circuit protection, heating element and others.

18

EXPERIMENT 2: TEMPERATURE MEASUREMENT

USING TYPE K THERMOCOUPLE

OBJECTIVE

To explore the working principle of Type K Thermocouple.

To explore the relation between voltage output and temperature

THEORY

Thermocouple

A thermocouple consists of two different metals that produce a voltage at the junction related to

a temperature difference. Thermocouples are a widely used as a temperature sensor for

measurement and control, and can also be used to convert heat into electric power. They are

inexpensive, are supplied fitted with standard connectors, and can measure a wide range of

temperatures. The main limitation is accuracy: system errors of less than one degree Celsius (C)

can be difficult to achieve. Any junction of dissimilar metals will produce an electric potential

related to temperature. Thermocouples for practical measurement of temperature are junctions of

specific alloys which have a predictable and repeatable relationship between temperature and

voltage. Different alloys are used for different temperature ranges. Properties such as resistance

to corrosion may also be important when choosing a type of thermocouple. Where the

measurement point is far from the measuring instrument, the intermediate connection can be

made by extension wires which are less costly than the materials used to make the sensor.

Thermistors

Thermistors consist of semi-conducting polycrystalline material. In the production of

temperature sensors copper dioxide (CuO2) is preferred. It demonstrates a sever (non-linear)

drop in resistance for an increase in temperature. It possesses a negative temperature coefficient,

which is the reason why these sensors are called NTC resistors.

Features of NTC and PTC thermistors

NTC sensors possess a high sensitivity, which is easily 10 times higher than that of metal

resistance thermometers. The non-linearity of NTCs and their broad manufacturers' tolerances

exclude them from use for precision instruments. In the temperature range between -60℃ and

+150℃ they are frequently used in the area of household appliances and medical technology

because of their high sensitivity and corresponding simple circuitry.PTCs behave in the same

manner below the threshold temperature. The resistance lies only somewhat higher than for

NTCs, because, due to the mixture of a ferroelectric material to the semiconductor material an

additional resistance of both components results (series connection). However, with increasing

19

temperature a strong increase in resistance is observed within a narrow temperature range, which

is caused so rapidly by the sudden cancelling of a uniform orientation of all magnetic forces in

the ferroelectric material. Through thermal motion an amorphous crystal structure is produced,

which results in a considerable prolongation of the current paths, on which the electrons move

through the PTC. If this transition is completed, the resistance then drops again as the rise in

temperature continues. Thus the function R(T) of the PTC follows the characteristic of its

semiconductor components, supplemented by the characteristics of its ferroelectric components.

Temperature function and temperature coefficient of NTC thermometers

The resistance R(T) = RT of NTC materials can be described as a function of the temperature

using the following equation:

RT = Ae𝐵/𝑇(5)

The material constant B is given in Kelvin, e.g. B = 3800 K. The constant A gives the resistance

for infinitely high temperature. As the sensor cannot register this temperature, the constant A

cannot be used as a practical parameter. The requirements for practical application can be better

satisfied with the following dependency RT. For this the reference temperature To = 20℃ is

used, for which the resistance has its nominal value Ro. Due to the fact that in the above equation

only A is unknown, the equation is then solved for A, which is inserted into 𝑅𝑇:

𝑅(𝑇𝑜) = 𝑅𝑜 = 𝐴𝑒𝐵/𝑇𝑜 𝐴 = 𝑅𝑜𝑒

𝐵/𝑇𝑜 (6)

Sub (6)into (5)

RT = RoeB(1/T − 1/To ) (7)

PROCEDURE

1. The 3pin plug is plugged to 220VAC powers supply. Switch ON the power supply.

2. The MCB/ELCB is switched ON.

3. The main power supply for the apparatus was Switch ON.

4. Tap water poured into the hot water. The water level must at least half of the pot.

5. The small cap (on top of the hot water pot) removed from the hot water pot.

6. Type K thermocoupleconnected (to port 1) and placed it into the hot water pot.

7. Ensure the selector switch is switches to 1.

8. The temperature meter voltage connected to output port to digital mV meter.

9. The values from Type K temperature meter and mV meter was recorded into table.

10. Turn ON the water heater (ensure the hot water pot is turn ON as well).

11. For every 5 °C interval, the temperature reading and the voltage reading were recorded.

12. Step 11 is repeated until the water boiled.

20

DATA AND RESULTS

Type K

Time (min) Voltage(mV) Temp(oC)

0 -0.673 23.7

2 -0.575 26.2

4 -0.351 31.8

6 -0.124 37.6

8 0.080 42.6

10 0.303 48.2

12 0.535 53.9

14 0.740 59.0

16 0.945 63.8

18 1.140 68.7

20 1.314 72.9

22 1.465 76.6

24 1.570 79.1

Table 2.1 Type K experiment result

21

0

10

20

30

40

50

60

70

80

90

0 5 10 15 20 25 30

Graph of Temperature,T vs time,t

y = 0.040x - 1.641

-1

-0.5

0

0.5

1

1.5

2

0 10 20 30 40 50 60 70 80 90

Graph of Voltage,V vs Temperature,T

22

DISCUSSION

As we can see from the table and the graph obtained, we can see that the

temperature decrease when the voltage increases. This is due to the NTC probe possesses

a negative temperature coefficientand responded very similar to semiconductors. The

temperature affects the NTC can be explain by the semiconductor mechanism, the

resistance R(T) = RT of NTC materials can be describe as a function of the temperature

using the following equation: RT = AeB/T

, where A is an unknown and B is the material

constant.

For both cases, one of the graph is linear (Voltage against Temperature) and one is

not (Temperature against Time). Compare to the both experiment, two graphs should be

perform a linear graph function, but due to some error that occur, we found out that the

graph doesn`t perform a smooth linear line as we thought. This is due to the error occur at

the multimeter we measure, the meter reading of temperature, lack of experience in

measurement lab and most importantly is the liner graph is just a prediction, so, it doesn`t

perform an accurate function that we predict.

With these two experiment, we found out that, the NTC probe has a much more

higher sensitivity compare to PT 100 Resistance Thermometer. As we can see from the

graphs, a slight increase in temperature will cause a large decrease in voltage drop. This

is due to the behavior of the semiconductor as the material of NTC probes.

Sensitivity of thermocouple(mV/°C) = 0.006

25.1 = 0.00024

CONCLUSION

We finally know how the type K Thermocouple works and we found out the

relationship between voltage output and temperature.We can see that the temperature

decrease when the voltage increases. This is due to the NTC probe possesses a negative

temperature coefficientand responded very similar to semiconductors.For both cases,

both graphs are not linear (Voltage against Temperature) and (Temperature against

Time). Compare to the both experiment, two graphs should perform a linear graph

function, but due to some error that occur, we found out that the graph doesn`t perform a

smooth linear line as we thought. We achieved our objective in this experiment.

23

EXPERIMENT 3: HUMIDITY

OBJECTIVE

Understanding of whirling pyschorometer (hygrometer).

Understanding of wet and dry bulb thermometer.

Measurement of ambient humidity using dry and wet bulb.

THEORY

Humidity is the amount of water vapor in the air. Relative humidity is defined as the ratio of the

partial pressure of water vapor in a parcel of air to the saturated vapor pressure of water vapor at

a prescribed temperature. Humidity may also be expressed as specific humidity. Relative

humidity is an important metric used in forecasting weather. Humidity indicates the likelihood of

precipitation, dew, or fog. High humidity makes people feel hotter outside in the summer

because it reduces the effectiveness of sweating to cool the body by reducing the evaporation of

perspiration from the skin. This effect is calculated in a heat index table.

Hygrometers are instruments used for measuring humidity. A simple form of a hygrometer is

specifically known as a psychrometer and consists of two thermometers, one of which includes a

dry bulb and the other of which includes a bulb that is kept wet to measure wet-bulb temperature.

Modern electronic devices use temperature of condensation, changes in electrical resistance, and

changes in electrical capacitance to measure humidity changes. Hygrometers measure humidity

while psychrometers measure relative humidity in the air.

In a psychrometer, there are two thermometers, one with a dry bulb and the other with a wet

bulb. Evaporation from the wet bulb lowers the temperature, so that the wet-bulb thermometer

usually shows a lower temperature than that of the dry-bulb thermometer, which measures dry-

bulb temperature. When the air temperature is below freezing, however, the wet bulb is covered

with a thin coating of ice and yet may be warmer than the dry bulb. Relative humidity is

computed from the ambient temperature as shown by the dry-bulb thermometer and the

difference in temperatures as shown by the wet-bulb and dry-bulb thermometers. Relative

humidity can also be determined by locating the intersection of the wet- and dry-bulb

temperatures on a psychrometric chart. One device that uses the wet/dry bulb method is the sling

psychrometer, where the thermometers are attached to a handle or length of rope and spun

around in the air for a few minutes.

There is a definite analytical relationship between the dry-bulb, wet-bulb and dew-point

temperatures of a mixture and its humidity. A determination of any two of these temperatures

maybe used to calculate the humidity. The classic method used for humidity determination in

large open spaces is a measurement of the dry-bulb and wet-bulb temperature with sling

psychrometer. Both thermometers are rotated with a speed of about 5 m/s and the temperatures

are recorded. The vapor pressure of the mixture may then be calculated with Carrier’s equation:

24

pυ = pgw – [ ( p – pgw ) ( TDB – TWB ) / Kw – TWB

pυ = actual vapor pressure

pgw = saturation pressure corresponding to wet-bulb temperature

p = total pressure of mixture

TDB = dry-bulb temperature, °F or °C

TWB = wet-bulb temperature, °F or °C

Kw = 2800 when T is in °F

= 1537.8 when T is in °C

PROCEDURE

Psychrometer

1. The whirling psychrometer was prepared. The water was filled into the whirling

psychrometer water container.

2. The water was allowed to wet the cloth of the wet-bulb thermometer after refilling the

whirling psychrometer.

3. The black handle was pulled of the whirling psychrometer so that it is perpendicularto the

dry and wet-bulb thermometer.

4. The initial reading was state down for the wet and dry bulb thermometer.

5. The whirling psychrometerrotated for about 1 minute and wait for the temperature to

stable.

6. The reading was taken for the wet and dry bulb thermometer and records it into the table.

7. From the chart given, the humidity of the ambient was determined(Note: You have to

calculate the depression of wet-bulb).

Humidity dail gauge

1. The gage placed at open space in the room.

2. The gage allowedreaching to constant reading for few minute.

3. The reading of the humidity dail gage was taken and recorded.

25

DATA AND RESULTS

Wet Bulb

Dry Bulb

Difference between

dry & wet bulb

Initial Reading (̊C) 24.0 26.0 2

Final Reading (̊C) 22.0 26.0 4

Humidity from

psychrometeric

Chart

70%

Humidity reading

from dail gage 77%

Table 3.1 Wet and Dry Bulb and Humidity Measurement

Sample calculation :-

Initial reading.

Difference between dry & wet bulb = dry bulb – wet bulb

= 26.0 – 24.0

= 2

26

DISCUSSION

1. We observe that the decreasing temperature of wet bulb is abaout 2 ᵒC, while

the dry bulb maintains with no changes of temperature.

2. The difference of wet bulb and dry bulb in initial reading is 2ᵒ C, while

different in final reading is 4 ᵒC.

3. The ambient humidity that was calculated is 71%.

4. The error occur during the experiment is the inconsistent rotation of the

hygrometer.

27

CONCLUSION

We learned how to use whirling psychrometer( hygrometer) with the concept of

wet and dry bulb meter. We measured ambient humidity using dry and wet bulb.

When the thermometer bulb is dry, the humidity reading is high. When the thermometer

bulb is wet, the humidity reading is low. The objective of this experiment is achieved.

REFERENCES

Measurement Lab manual(Experiment 3).

Experimental Method for Engineers, JP Holman, 7th

Edition, Mc Graw-Hill

International Edition