Final Year Instrumentation and Control Projects

This post is regarding the Project topics for Instrumentation and Control Engineering Discipline final year Students.

I will first give out the instrumentation and control engineering project titles first, if you need any help in that particular topic, you may contact me in the comment form..

Industrial machine Data (sensors) Transmitting, Receiving And Control Through Walkie Talkie.
Temperature Reding And Controlling Through Fibre Cable.
Wireless Controlling For Boiler / Gas Stove temperature / Timer / Flame Controlling System.
Finger print recognition.
Using SCADA for Process Control
Data Acquisition for Process Control using Lab View Software.
PLC based Dc Servo Motor Control System
Instrumentation Project on POWER GRID CONTROL THROUGH PC.
Temperature Reading Data - Transmitted Through Fibre Cable.


Introduction to Correction calibration

All measuring instruments are to prove themselves their ability to measure reliably and accurately. For this, the results of measurement are to be compared with higher standards which are traceable to national or international standards. The procedure of this is termed as calibration.

Calibration is thus a set of operation that establishes the relationship between the values that are indicated by measuring instrument and the corresponding known value of measurand.

Thus calibration of measuring instrument means introducing an accurately known sample of the variable that is to be measured and then observing the system’s response. Then the measuring instrument is checked and adjusted until its scale reads the introduced accurately known sample of the variable.

It should be further noted that an instrument is calibrated at one place and is put to use at some other place. Care should be taken to see that the instrument is used at a place where the environment has the same conditions as that of the place where the instrument was calibrated to ensure that the instrument gives correct readings.


Dew Point Meter

Basic Principle of Dew Point Meter

By Cooling at constant pressure if the temperature of air is reduced, the water-vapour in the air will start to condense at a particular temperature. This temperature is called dew point temperature.

Description of Dew Point Meter

The main Parts of arrangement are

  • A shiny surface (mirror) is fixed with a thermocouple.
  • A nozzle is providing a jet of air on the mirror.
  • A light source focused constantly on the mirror.
  • A photo cell to detect the amount of light reflected from the mirror.

Operation of Dew Point Meter

  • The mirror is constantly cooled by a cooling medium. The cooling medium is maintained at a constant temperature.
  • To this mirror is attached a thermocouple whose leads are connected to a millivoltmeter.
  • Constantly a light is made to fall in an angle on the mirror and the amount of reflected light is sensed by a photo cell.
  • Now an air jet is made to fall in an angle on the mirror and the water-vapor (moisture) contained in the air starts condensing on the mirror and they appear as small drops (dew) on the mirror.
  • This moisture (dews) formed on the mirror reduces the amount of light reflected from the mirror and it is detected by photocell. When for the first time, there is a change in amount of transmitted light; it becomes an indication of dew formation.
  • At this instance (that is, when the due formation is detected first), the temperature indicated by the thermocouple attached to the mirror becomes the dew point temperature.
  • Thus this arrangement is used to determine the time at which the dew appears for the first time and dew point temperature.

Application of dew point meter

  • This instrument is used on ships to protect cargoes from condensation damage by maintaining the dew point of air in holds lower than the cargo temperature.
  • Used in industries for determining dew point.


There are limitations in cooling fluids and light measurement.


Electrical Humidity Sensing Absorption Hydrometer

Basic Principle:

A change in resistance with change in humidity is taken as a measure of humidity.

This is type of Electrical Humidity sensing Absorption Hydrometer, know more about mechanical humidity sensing methods using Hair Haydrometer


The main Parts of this arrangements are, two metal electrodes which are coated and separated by a humidity sensing hygroscopic salt (lithium chloride). The leads of the electrodes are connected to a null – balance wheat stone bridge.


When the humidity of the atmosphere is to be measured, the electrodes coated with lithium chloride are exposed to atmosphere. Humidity variation causes the resistance of the chemical (lithium chloride) to change. That is, the chemical absorbs moisture or loss moisture and causes a change in resistance.

Higher the humidity (RH) in the atmosphere more will be the humidity absorbed by lithium chloride and lower will be the resistance.

Lesser the humidity (RH) in the atmosphere less will be the humidity absorbed by lithium chloride and higher will be the resistance.

The change in resistance using a Wheatstone bridge and this change in resistance becomes a measure of humidity (RH) present in the atmosphere.


These hydrometers are used under constant temperature conditions to measure humidity of atmosphere.
The accuracy of this instrument is in +/- 25%.
The response is of the order of few seconds.


These instruments should not be exposed to 100% humidity as the resulting absorption by the chemical (lithium chloride) might damage the instrument.
If these devices are not used under constant temperature conditions, temperature correction must be made.


Hair Hydrometer

Basic Principle

Due to humidity, several materials experience a change in physical, chemical and electrical properties. This property is used in transducer that are designed and calibrated to read relative humidity directly.

Hair hydrometer is a type of absorption hydrometer and uses the mechanical humidity sensing technique.

Certain hygroscopic materials such as human hair, animal membranes, wood, paper, etc., undergo changes in linear dimensions when they absorb moisture from their surrounding air. This change in linear dimension is used as the measurement of humidity present in air.

Description of Hair Hydrometer

The main Parts of hair hydrometer are,

Hair HydrometerHuman hair is used as the humidity sensor. The hair is arranged in parallel beam and they are separated from one another to expose them to the surrounding air/atmosphere. Number of hairs are placed in parallel to increase mechanical strength.

This hair arrangement is placed under small tension by the use of a tension spring to ensure proper functioning.

The hair arrangement is connected to an arm and a link arrangement and the link is attached to a pointer pivoted at one end. The pointer sweeps over a humidity calibrated scale.

Operation of Hair Hydrometer

When the humidity of air is to be measured, this air is made to surround the hair arrangement and the hair arrangement absorbs the humidity from the surrounding air and expands or contracts in the linear direction.

This expansion or contraction of the hair arrangement moves the arm & link and thus the pointer to a suitable position on the calibrated scale and thus indicating the humidity present in the air/atmosphere.

Note: These Hair hydrometers are called membrane hydrometers when the sensing element is a membrane.

Applications of Hair Hydrometer

These hydrometers are used in the temperature range of 0’C to 75’C.
These hydrometers are used in the RH (Relative Humidity) range of 30 to 95%.

Limitations of Hair Hydrometer

These Hydrometers are slow in Response
If the Hair hydrometer is used constantly, its calibration tends to change.


Pressure Measuring Instruments

McLeod Vacuum Gauge

A known volume gas is compressed to a smaller volume whose final value provides an indication of the applied pressure. I have given a brief post on the equations used with good construction diagram of McLeod Vacuum Gauge

Strain Gauge Pressure Cell

Based on a principle

When a closed container is subjected to the appilied pressure, it is strained (that is, its dimension changes). Measurement of this strain with a secondary transducer like a strain gauge ( metallic conductor) becomes a measure of the appilied pressure.

The Two types of Strain Gauge Pressure Cell, Flattened tube pressure cell and Cylindrical type pressure cell are discussed.

Elastic diaphragm gauges

When an elastic transducer (diaphragm is this case) is subjected to a pressure, it deflects. This deflection is proportional to the appilied pressure when calibrated.

Bourdon tube Pressure Gauge

when an elastic transducer ( bourdon tube in this case ) is subjected to a pressure, it defects. This deflection is proportional to the applied pressure when calibrated.

Manometer with equal unequal limb types

This is the most simple and precise device used for the measurement od pressure. It consists of a transparent tube constructed in the form of an elongated 'U', and partially filled with the manometeric fliud such as mercury. The purpose of using mercury as the manometeric fluid is that their specific gravity at various temperatures are known exactly and they dont stick to the tube. The two common types of manometers are the equal limb type and unequal limb type.

Dead Weight Tester

The dead weight tester apparatus consists of a chamber which is filled with oil free impurities and a piston – cylinder combination is fitted above the chamber as shown in diagram. The top portion of the piston is attached with a platform to carry weights. A plunger with a handle has been provided to vary the pressure of oil in the chamber. The pressure gauge to be tested is fitted at an appropriate plate.

Pressure Measurement using U-tube Manometer
A well known very simple device used to measure the pressure is the U-tube manometer. The name U-tube is derived from its shape. U-tube manometer is shown below.

Terms related to pressure

All the important terms related to Pressure measurement like Atmospheric pressure, Absoulte pressure, Gauge Pressure, Vacuum pressure, Static Pressure, Total or Stagnation pressure, Dynamic – or – Impact – or – Velocity pressure and more are discussed.

And This Post will be updated regularly whenever i post a topic about pressure measurement using different devices.

Please Post your Comments below.


Sling Psychrometer

Sling Psychrometer is used to measure both the dry bulb and wet bulb temperatures at time. These temperatures are a measure of humidity content in air.

Description of Sling Psychrometer

The main parts of the instrument are

sling psychrometer
The instrument frame which holds the thermometers.

One mercury in glass thermometer whose sensing bulb is bare to directly contact the air and to measure the temperature which is called as the dry-bulb temperature.

One mercury in glass thermometer whose sensing bulb is covered with a cotton or muslin wick made wet with pure water. This sensing bulb covered with the cotton wick moistened is made to contact the air and the temperature indicated by this thermometer is called as the wet bulb-thermometer.

The instrument frame carrying the thermometer is covered by a glass casing.

A swivel handle is attached to frame-glass casing – thermometer arrangement to ensure that the air at the wet bulb always in immediate contact with the wet wick.

When a thermometer bulb is directly exposed to an air-water vapour mixture, the temperature indicated by the thermometer is the dry-bulb temperature.

When a thermometer bulb is covered by a constantly wet wick and if the bulb covered by the wet wick is exposed to air water vapour mixture, the temperature indicated by the thermometer is the wet bulb temperature.

Operation of Sling Psychrometer.

In order to measure the dry bulb and wet bulb temperature, the Psychrometer frame – glass covering – thermometer arrangement is rotated at 5 m/s to 10 m/s to get the necessary air motion.

Note: An important condition is that correct/accurate measurement of wet bulb temperature is obtained only if air moves with velocity around the wet wick. In order to get this air velocity, the Psychrometer is being rotated.

The thermometer whose bulb is bare contacts the air indicates the dry bulb temperature.

At the same time, the thermometer whose bulb is covered with the wet wick comes in contact with the air and when this pass on the wet wick present on the bulb of the thermometer, the moisture present in the wick starts evaporating and a cooling effect is produced at bulb. Now the temperature indicated by the thermometer is the wet bulb thermometer which will naturally be lesser than the dry bulb temperature.

Note: If the Psychrometer is rotated for a short period, then the wet bulb temperature recorded will not be proper.
Note: If the Psychrometer is rotated for a longer period, the wick will get dried soon and the wet bulb temperature will not be at its minimum value.

Application of Sling Psychrometer

  1. It is used for checking humidity level in air-conditioned rooms and installations.
  2. It is used to set and check hair hygrometer.
  3. It is used in the measurement range of 0 to 100% RH.
  4. It is used for measuring wet bulb temperature between 0’C to 180’C.

Limitation of Sling Psychrometer

  1. The measured medium is disturbed due to the act of measurement. The evaporation process at the wet bulb will add moisture to the air.
  2. It cannot be used in automation requirement situations.
  3. It cannot be used for continuous recording purpose.
  4. If the wick is covered with dirt, the wick will become stiff and its water absorbing capacity will reduce, however, a stiff/dirty wick will resume normalcy when boiled in hot water.


Humidity / Dampness Measurement


The amount of water vapour contained in air or gas is called as humidity. This humidity affects human comforts and many industrial process as in case of chemical industries, garments industries, paper industries, food industries, leather industries, pharmaceutical industries, precision equipment manufacturing, etc. hence, study of humidity is important. Let us define some common terms related to humidity measurement.


The amount of water vapour contained in air or gas is called as humidity. It is usually measured as absolute humidity, relative humidity or due point temperature.

Dry air

When there is no water vapour contained in the atmosphere, it is called dry air.

Moist air

When there is water vapour present in the atmosphere, it is called moist air.

Saturated air

Saturated air is the moist air where the partial pressure of water-vapour equals the saturation pressure of steam corresponding to the temperature of air.

Absolute humidity

It is the mass of water vapour present per unit volume. In other words, it is the quantity of the water vapour present in air and its unit is grams per cubic meter of air.

Relative humidity RH

Relative humidity = (water vapour pressure actually present)/(water vapour pressure required of saturation) at a given.

Here a comparison is made between the humidity of air and humidity of saturated air at the same temperature and pressure.
It should be noted that if relative humidity is 100%, it is saturated air. That is, the air contains all the moisture it can hold.
It should also be noted that the degree of saturation (percentage of relative humidity) of air keeps on changing with temperature.

Humidity ratio or specific humidity

For a given volume of air water vapour mixture,

Humidity ratio = (mass of water – vapour)/mass of dry air

Dew point temperature

By continuous cooling at constant pressure if the temperature of air is reduced, the water-vapour in the air will start to condense at a particular temperature. The temperature at which the water vapour stats condensing is called as dew point temperature.

Dry-bulb temperature

When a thermometer bulb is directly exposed to an air-water vapour mixture, the temperature indicated by the thermometer is the dry-bulb temperature.
This dry-bulb temperature is not affected by the moisture present in the air, that is, the temperature of air is measured in a normal way by the thermometer.
The dry bulb is used to distinguish the normal temperature measured from the temperature measured by the wet-bulb.

Wet-bulb temperature

When a thermometer bulb is covered by a constantly wet wick, and if the bulb covered by the wet wick is exposed to air-water vapour mixture, the temperature indicated by the thermometer is wet-bulb temperature.

When air is passed on the wet wick present on the bulb of the thermometer, the moisture present in the wick strats evaporating and this creates a cooling effect at the bulb. The bulb now measures the thermo dynamic equilibrium temperature reached between the cooling effected by the evaporation of water and heating by convection.

Wet-bulb depression

Wet-bulb depression = (dry bulb temperature) – (wet bulb temperature)

Always dry-bulb temperature is higher than the wet bulb temperature.

Percentage humidity

Percentage humidity = weight of water vapour in a unit weight of air/ weight of water vapour in same weight of air if the air were completely saturated at the same temperature.


Virutal Instrumentation Software - LabVIEW

Today in this post, I  like to present you a very famous and helpful software in our instrumentation and control field which is nothing but LabVIEW.

It is completely related to virtual instrumentation. And to know about virtual instrumentation

Here is a video about LabView.

You can download a student edition in  or download a pirated version in torrents site.

Some useful link related to Labview


McLeod Vacuum Gauge

Basic Principle of McLeod Vacuum Gauge:

A known volume gas is compressed to a smaller volume whose final value provides an indication of the applied pressure. The gas used must obey Boyle’s law given by;


Where, P1 = Pressure of gas at initial condition (applied pressure).
P2 = Pressure of gas at final condition.
V1 = Volume of gas at initial Condition.
V2 = Volume of gas at final Condition.

Initial Condition == Before Compression.
Final Condition == After Compression.

A known volume gas (with low pressure) is compressed to a smaller volume (with high pressure), and using the resulting volume and pressure, the initial pressure can be calculated. This is the principle behind the McLeod gauge operation.

Description of McLeod Vacuum Gauge:

The main parts of McLeod gauge are as follows:
McLeod vacuum gauge

A reference column with reference capillary tube. The reference capillary tube has a point called zero reference point. This reference column is connected to a bulb and measuring capillary and the place of connection of the bulb with reference column is called as cut off point. (It is called the cut off point, since if the mercury level is raised above this point, it will cut off the entry of the applied pressure to the bulb and measuring capillary. Below the reference column and the bulb, there is a mercury reservoir operated by a piston.

Operation of McLeod Vacuum gauge:

The McLeod gauge is operated as follows:

The pressure to be measured (P1) is applied to the top of the reference column of the McLeod Gauge as shown in diagram. The mercury level in the gauge is raised by operating the piston to fill the volume as shown by the dark shade in the diagram. When this is the case (condition – 1), the applied pressure fills the bulb and the capillary.
Now again the piston is operated so that the mercury level in the gauge increases.

When the mercury level reaches the cutoff point, a known volume of gas (V1) is trapped in the bulb and measuring capillary tube. The mercury level is further raised by operating the piston so the trapped gas in the bulb and measuring capillary tube are compressed. This is done until the mercury level reaches the “Zero reference Point” marked on the reference capillary (condition – 2). In this condition, the volume of the gas in the measuring capillary tube is read directly by a scale besides it. That is, the difference in height ‘H’ of the measuring capillary and the reference capillary becomes a measure of the volume (V2) and pressure (P2) of the trapped gas.

Now as V1,V2 and P2 are known, the applied pressure P1 can be calculated using Boyle’s Law given by;

P1V1 = P2V2

Let the volume of the bulb from the cutoff point upto the beginning of the measuring capillary tube = V

Let area of cross – section of the measuring capillary tube = a
Let height of measuring capillary tube = hc.


Initial Volume of gas entrapped in the bulb plus measuring capillary tube = V1 = V+ahc.

When the mercury has been forced upwards to reach the zero reference point in the reference capillary, the final volume of the gas = V2 +ah.

Where, h = height of the compressed gas in the measuring capillary tube
P1 = Applied pressure of the gas unknown.
P2 = Pressure of gas at final condition, that is, after compression
= P1+h

We have, P1V1 = P2V2 (Boyle’s Law)
Therefore, P1V1= (P1+h)ah

P1V1 = P1ah + ah^2

P1V1-P1ah = ah^2

P1 = ah^2/(V1-ah)

Since ah is very small when compared to V1, it can be neglected.

Therefore, P1 = ah^2/V1

Thus the applied pressure is calculated using the McLeod Gauge.


The McLeod Gauge is used to measure vacuum pressure.

Advantages of the McLeod Gauge:

  • It is independent of the gas composition.
  • It serves as a reference standard to calibrate other low pressure gauges.
  • A linear relationship exists between the applied pressure and h
  • There is no need to apply corrections to the McLeod Gauge readings.

Limitations of McLeod Gauge:

  • The gas whose pressure is to be measured should obey the Boyle’s law
  • Moisture traps must be provided to avoid any considerable vapor into the gauge.
  • It measure only on a sampling basis.
  • It cannot give a continuous output.


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