02230271
BE Mechanical
MEC202
Assignment 1
College of Science and Technology
Measuring Instruments:
1) Screw Gauge:
Screw Gauge is a device or a precision instrument used for determining the minor dimensions of
objects (up to a scale of 0.01mm).
Fig1: Screw Gauge
⁕ Components:
i) Frame: U-shaped frame which retains the anvil and spindle. Cannot be moved.
ii) Anvil: A stationary metal surface onto which object to be measured is placed.
iii) Spindle: A screw that rotates towards the anvil when you rotate the thimble.
iv) Sleeve: A cylindrical structure where the main/pitch scale is marked.
v) Thimble: A part that rotates around a circular section where a circular scale is marked.
vi) Ratchet: A knob that prevents over-tightening allowing constant pressure to be maintained.
⁕ Formula:
Least Count =
Pitch of the screw
No. of Circular scale divisions
⁕ Working Principle:
Works on the principle of a screw mechanism. The measurement is read from the main scale and
circular scale where the rotation of the thimble causes the spindle to move, and the calibrated
screw pitch enables precise measurement up to 0.5 mm or 1 mm. Thus, the screw gauge
measures the small movements of the spindle through the circular scale, making it possible to
measure the minor dimensions accurately.
⁕ Observation:
The thickness of the mild steel block was 10 mm.
2) Vernier Caliper:
A Vernier Caliper is also a precision measuring instrument used to measure an object's internal,
external, and depth dimensions using measuring jaws with an accuracy up to ±0.02 mm.
Fig2: Vernier Caliper
⁕ Components:
i) Main Scale: Measures the total length of an object.
ii) Vernier Scale: Measures minor increments of length.
iii) Fixed Jaw: A stationary jaw that measures the exterior parts of an object.
iv) Movable Jaw: Attached to vernier scale and measure the interior parts of an object.
v) Lower Jaws: Used to measure external dimensions and provide a secure grip.
vi) Upper Jaws: Smaller than the lower jaws that measure the inner dimensions of objects.
⁕ Formula:
Least Count =
Value of one main scale division
Number of vernier scale division
⁕ Working Principle:
Works on the principle of alignment of measurement markings on the main scale and the vernier
scale for accurate readings. The vernier scale slides along the main scale to provide precise
measurements. The reading is obtained by adding the value of the vernier scale reading to the
main scale reading when marking on the vernier scale matches the main scale.
⁕ Observation:
The thickness of the mild steel block was 1 cm.
3) Measuring Tape:
A measuring tape is a flexible instrument used for measuring length. It is marked in centimeters
(cm) and inches (in) and is made of various materials such as fiberglass, cloth, plastic, and metal
strips.
Fig3: Measuring Tape
⁕ Components:
i) Tape Blade: Flexible metal strip used to measure the length of objects.
ii) Case: Encloses the tape blade.
iii) Thumb Lock: Used to hold the tape blade in place with your thumb.
iv) Hook/Tang: To hook onto the edge of an object being measured.
⁕ Working Principle:
Depends on the elastic deformation of a spring. The measuring tape is wound around a spring
and the scale is fixed to the tape. The spring experiences elastic deformation when the tape is
pulled out, extending the tape’s length. The tape’s length is reduced when it is released because
the spring returns to its initial position.
⁕ Observation:
The width of the table was 23.6 cm.
4) Stainless Steel Rule:
A simple and basic tool, flat and rigid in structure, used for measuring the length of an object up
to 1 meter with an accuracy of ±0.5 mm made of stainless steel with marked graduations of
centimeters and inches.
Fig4: Stainless Steel Rule
⁕ Types:
i) Flexible Rules: Used for measuring curved surfaces.
ii) Rigid Rules: Used for measuring straight edges.
⁕ Working Principle:
Works on direct measurement by placing the rule alongside or on top of the object and aligning
the zero mark with the end of the object. The measurement is determined directly from the scale
by reading the marking that aligns with the other end of the object.
⁕ Observation:
The length of the steel box was 29.1 cm.
5) Try Square:
Try square is a woodworking or metalworking tool used for marking and checking 90-deg angles
on the workpiece (squareness of corners, edges, and flat surfaces).
Fig5: Try Square
⁕ Types:
i) Steel Try Square: Most common type, made of steel, with a blade attached to a handle at 90o.
ii) Wooden Try Square: Traditional and made of hardwood that has a blade secured through
wooden pins.
iii) Engineering Try Square: Made of cast iron or steel and a large and heavy-duty tool used in
industries.
⁕ Working Principle:
Works on the principle of direct measurement where you place the try square blade across the
material you want to test or mark. For the blade to lie flat across the surface, enable the thicker
portion of the handle to extend over the edge and press the handle against the edge of the
material.
⁕ Observation:
The corner of the table was aligned and 90o.
6) Spirit Level:
A spirit level is an instrument used for measuring or aligning the surface, ensuring that it is either
perfectly horizontal or vertical. It uses a sealed vial filled with liquid and an air bubble where the
bubble moves with the vial and aligns with the center when the surface being measured is rightly
positioned.
Fig6: Spirit Level
⁕ Components:
i) Body: Provides longevity and straight edge, made of metal or plastic.
ii) Glass Tube (Vial): A sealed transparent tube filled with liquid and an air bubble.
iii) Ether Vapor Bubble: Indicates the level when it is centered between the marked lines.
iv) Markings: Lines on the vial that help to determine precise leveling.
⁕ Working Principle:
Works on the principle of gravity where the air bubble in the slightly curved vial naturally moves
to the highest point and when the surface is perfectly leveled, the bubble moves and aligns
perfectly between the marked lines on the vial.
⁕ Observation:
The surface was aligned as the air bubble was at the center of the marked lines.
7) Digital Angle Gauge:
A digital angle gauge/finder is a contemporary instrument to measure angles precisely.
Embedded with electronic sensors, it rapidly determines the angle and displays it on the digital
screen making measurement more precise and easier.
Fig7: Digital Angle Gauge
⁕ Components:
i) Digital Screen: Displays angle measurement often to the nearest decimal point.
ii) Magnetic Base: Allows the device to firmly attach to metal surfaces.
iii) Body Indicators: Markings on the sides that help align the device while measuring.
⁕ Working Principle:
Works on the principle of direct measurement by setting it on a flat surface where the angle will
be displayed on the digital screen. Also, when the angle finder is placed on a metal surface, the
magnetic base will keep it in place and give us the angle.
⁕ Observation:
The metallic surface was at an angle 88.1o.
8) Digital Contact Tachometer:
A contact tachometer requires contact with a rotating object to measure its RPM (revolutions per
minute). Depending on the model, they use either a magnetic sensor or an optical encoder. To
obtain an accurate reading, direct contact with the shaft or rotating component must be
maintained.
Fig8: Digital Contact Tachometer
⁕ Components:
i) Contact Tip: Physically contact and rotate with the rotating object.
ii) Shaft Encoder/Sensor: Converts the rotational motion into an electrical signal. Either a
magnetic sensor or an optical encoder.
iii) LCD Screen: Displays the measured RPM.
⁕ Working Principle:
Determines the rotational speed of an object with direct physical contact with it. As the contact
tip of the tachometer rotates with the object, an internal sensor transforms the motion of the
contact tip into electrical pulses. A microcontroller uses a calibration factor to then determine the
rpm after counting these pulses over a time where the output will be displayed on the digital
screen.
⁕ Observation:
The gear was rotating at 140 rpm.
9) Laser Tachometer:
Like contact tachometer but uses a laser and is a non-contact tachometer. A laser tachometer
points a laser at a rotating object and measures the rpm. Depending on the model, laser
tachometers have different ranges but generally range from 1-2m.
Fig9: Laser Tachometer
⁕ Components:
i) Laser Diode: Emits laser beam which is pointed at the rotating object.
ii) Optical Sensor: Used to detect the reflected laser beam where each reflection corresponds to
one rotation generating electrical pulses.
iii) Lens and Optics: Focuses the laser beam and ensures accurate deflection of reflections.
⁕ Working Principle:
The laser diode emits a beam pointed at the rotating object, which reflects off a surface. The
optical sensor detects these reflected beams converting them to electrical impulses. A
microcontroller counts these pulses based on the pulse frequency and the result is displayed on
the screen.
⁕ Observation:
The steam engine was rotating at 339 rpm.
10) Stroboscope:
A stroboscope is an instrument that creates a stop-motion effect of a rotating object by
illuminating a high-intensity light on it. This stationary effect of a rotating object can be used to
study the rotating, vibrating, or oscillating objects to be measured.
Fig10: Stroboscope
⁕ Components:
i) Light Source: High-intensity LED that produces rapid flashes of light.
ii) Frequency Control: Helps control and adjust the rate of flash to match with the rotating object.
iii) Display Screen: Shows measured rpm, flash frequency, etc.…
iv) Housing: Provides ease of use and internal protection of components.
⁕ Working Principle:
Works on the principle of stroboscopic effect where flashes of light are illuminated on a rotating
object and when this flash frequency matches the object’s rotational speed, the object appears to
be stationary allowing for precise measurement of RPM.
⁕ Observation:
For 2 images, the rotation speed was 579 rpm. For 4 images, the rotation speed was 581 rpm.
References
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https://engineeringhulk.com/try-square-types-grades-accuracy-applications/
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https://www.electricaldeck.com/2021/07/stroboscope-tachometer-and-its-workingprinciple.html
What is Measuring Tape? Definition, Units, Example, Facts. (2022, April 25).
https://www.splashlearn.com/math-vocabulary/measurements/measuring-tape
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ElectricalWorkbook. https://electricalworkbook.com/stroboscope/
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& Reading Procedure. ElectricalWorkbook. https://electricalworkbook.com/spirit-level/