1) The document describes an experiment conducted to measure relative humidity using a wet and dry bulb hygrometer. 2) Students recorded the dry bulb temperature, temperature difference between wet and dry bulbs, and calculated relative humidity every minute for 30 minutes. 3) The mean relative humidity was calculated as 80.84% with a standard deviation of 2.05% based on the recorded measurements.

1. Dhaka University Of Engineering & Technology, Gazipur
Course Title: Textile Testing & Quality Management-I
Course Code: TE-4602(Sessional)
Experiment No: 01
Assignment Name: Study on Relative Humidity.
Submitted By:
Name: MD.MOSADDEK JAMAN
Student ID: 175056
Year/Semester: 4th
/1st
Session: 2020-21
Department: Textile Engineering
Signature
Date of
Performance
D M Y Date of Submission D M Y
28 08 2022 04 09 2022
Submitted To:
DR SHAFIQUL ISLAM
Associate Professor
Department: Textile Engineering

2. Abstract
Humidity is a measure of the amount of water vapor in the air. Humidity is the
concentration of water vapor present in the air. So Due to this, Moisture is
present in the textile fiber Which affected the textile fiber physical properties. In
general the fibres that absorb the greatest amount of moisture are the ones
whose properties change the most. In here, Relative Humidity is one of the most
important factor for the textile fiber. In this experiment we use wet and dry bulb
hygrometer to measure the relative humidity.
Theory
Relative Humidity(R.H): The ratio of the absolute humidity of the air to that of
air saturated with water vapor at the same temperature and pressure expressed
as a percentage.
Relative Humidity%=
𝐴𝑏𝑠𝑜𝑙𝑢𝑡𝑒 ℎ𝑢𝑚𝑖𝑑𝑖𝑡𝑦 𝑜𝑓 𝑎𝑖𝑟
𝐴𝑏𝑠𝑜𝑙𝑢𝑡𝑒 ℎ𝑢𝑚𝑖𝑑𝑖𝑡𝑦 𝑜𝑓 𝑎𝑖𝑟 𝑠𝑎𝑡𝑢𝑟𝑎𝑡𝑒𝑑 𝑤𝑖𝑡ℎ 𝑤𝑎𝑡𝑒𝑟
∗ 100
The absolute humidity is defined as the weight of water present in unit volume
of moist air measured in grams per cubic meter.
Wet and Dry Bulb Hygrometer: The wet and dry bulb hygrometer is
commonly used to measure the relative humidity in the testing laboratory and
textile mill. It has a very simple design. The relative humidity can be checked
easily by using this hygrometer.
Construction:
➢ There are two thermometers.
➢ Dry bulb thermometer: It is uncovered, determines the room temperature.
➢ Wet bulb thermometer: It is surrounded by a wet sleeve of muslin which
dips into a reservoir of distilled water, determines the lowest /cooling
temp.
Instrument
• Wet and Dry Bulb Hygrometer.

3. Diagram of Wet and Dry Bulb Hygrometer:
Working procedure: Measuring of relative humidity, wet and dry bulb
hygrometer is one of the most important instrument which gives us R.H without
any power consumption. Starting this experiment, At first we take a wet and dry
bulb hygrometer. After taking this, we pour some water into the wet bulb water
container. After putting water we wait 30 minute. Then we take the Dry bulb
temperature and wet bulb temperature and also differentiate the wet and dry
bulb temperature. Every one minute , every student take one wet and dry bulb
temperature from wet and dry bulb hygrometer. Depends on dry bulb
temperature and wet and dry bulb temperature we also take the RH% from the
Table. At least, we calculate the mean and standard deviation.
Data Table
Std Id Time
Dry Bulb
Tempr
(ºC)
Dry Bulb &Wet Bulb
Tempr diffn
(ºC)
R.H%
175001 2:30 30 3 80%
175002 2:31 30 3 80%
175003 2:32 30 3 80%

4. 175004 2:33 30 3 80%
175005 2:34 30 3 80%
175006 2:35 30 3 80%
175007 2:36 30 3 80%
175008 2:37 30 3 80%
175009 2:38 30 3 80%
175010 2:39 30 3 77%
175011 2:40 30 3 77%
175012 2:41 30 3 80%
175013 2:42 30 3 80%
175014 2:43 30 2.5 83%
175015 2:44 30 2.5 83%
175016 2:45 30 2.5 83%
175017 2:46 30 2.5 83%
175018 2:47 30 2 85%
175019 2:48 30 3 80%
175020 2:49 30 2.5 83%
175021 2:50 30 3 80%
175022 2:51 30 2.5 83%
175023 2:52 30 2.5 83%
175024 2:53 30 2 86%
175025 2:54 30 2 86%
175026 2:55 30 3 80%
175027 2:56 30 3 80%
175028 2:57 30 3 80%
175029 2:58 30 3 80%
175030 2:59 30 3 80%
175031 3:00 30 3 80%
175032 3:01 30 3 80%
175033 3:02 30 3 80%
175034 3:03 30 2 86%
175035 3:04 30 2 86%
175036 3:05 30 3 80%
175037 3:06 30 3 80%
175038 3:07 30 3 80%
175039 3:08 30 3 80%
175040 3:09 30 3 80%
175042 3:10 30 3 80%
175043 3:11 30 2 86%
175044 3:12 30 3.5 80%
175045 3:13 30 3 80%
175046 3:14 30 3 80%
175047 3:15 30 3 80%

5. 175048 3:16 30 3 80%
175050 3:17 30 3 80%
175051 3:18 30 3 80%
175052 3:19 30 3 80%
175053 3:20 30 3 80%
175054 3:21 30 3 80%
175055 3:22 30 3 80%
175056 3:23 30 3 80%
175057 3:24 30 3 80%
175058 3:25 30 3 80%
175059 3:26 30 3 80%
175060 3:27 30 3 80%
175061 3:28 30 3 80%
Result
Mean=((𝟒𝟒 ∗ 𝟖𝟎) + 𝟕𝟕 ∗ 𝟐) + (𝟖𝟑 ∗ 𝟒) + 𝟖𝟓 + (𝟖𝟑 ∗ 𝟑) + (𝟓 ∗ 𝟖𝟔))/𝟓𝟗
=80.84%
Standard Deviation:
=√
𝟐𝟒𝟑.𝟔𝟏
𝟓𝟗−𝟏
=2.05
Variance=S.D2
=92.05)2
=4.2025
Conclusion
After doing this experiment, we learn how to measurement the Relative
humidity from the instrument of wet and dry bulb hygrometer. After doing this
experiment we also learnt about humidity , Relative humidity and how to
measure and uses of wet and dry bulb hygrometer.