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Mechanical engineering relies heavily on taking precise measurements of physical quantities like length, mass, time, temperature, pressure, etc. Over the years, various types of mechanical measuring instruments have been developed to measure these quantities accurately. Here are some of the most common types of measuring instruments used in mechanical engineering:

Linear Measuring Instruments

These instruments measure linear dimensions like length, height, diameter, etc. Some common examples are:

Vernier Calipers - 

Used to measure internal and external diameters of objects with great precision. The vernier scale allows readings up to 0.1 mm or 0.01 inches.

Micrometers - 

Measure dimensions like diameter, length, and thickness. Different types are available like outside, inside, and depth micrometers. Resolution up to 0.01 mm is possible. 

Dial gauges - 

Measure small linear displacements and give very precise measurements. Used with magnetic stands for measuring shaft runout, flatness of surfaces, etc.

Linear scales - 

Simple fixed scales are used for larger measurements. Can be made of materials like steel. Graduated in mm or inches.

Angular Measuring Instruments 

These are used to measure angles and inclinations. Common examples are:

Bevel protractor - 

For measuring or setting angles on workpieces. Vernier scale gives precise angle measurements.

Clinometers - 

Measure angles of sloped surfaces or inclination of objects. Based on basic trigonometric principles. 

Sine Bar - 

Precisely sets unknown angles for machining workpieces. Works on sine principle.

Spirit levels - 

Simple levels to check if a surface is perfectly horizontal or vertical. Widely used for alignments.

Instruments for Measuring Surface Finish

Surface finish is critical in mechanical components. Instruments used include:

Surface roughness tester - 

Uses a stylus to traverse the surface and record minute variations. Gives quantitative roughness values. 

Mechanical comparators - 

Compare the surface finish against standard rough/smooth samples.

Optical interferometers - 

Use interference of light to measure surface finish. Very accurate.

Force and Torque Measurement 

Force measurement is done by:

Load cells - 

Use strain gauges attached to an elastic element. Widely used.

Hydraulic load cells - 

Measure force by the pressure of the fluid on the piston. For large forces.

Proving rings -

 Elastic rings are deformed by force. calibrate other force devices.

Torque is measured by:

Torque wrenches - 

Indirectly measure torque by pre-calibrated scale. Used for tightening bolts.

Torque meters - 

Sophisticated torque measurement instruments. Give a direct readout of torque.

Several other types of mechanical instruments are also used for the measurement of temperature, pressure, vibrations, flow, and more. Proper selection and usage of the right instrument are key for accurate measurements in mechanical systems. Regular calibration ensures reliability over time.