Subject:-Measurement & Metrology, Angle measuring instruments:-Sine bar , Clinometer , Bevel Protector.

  Angle measuring instrument:-

 →  The instrument which is used for measurement the slope of any object surface is called angle measuring instrument .

→There are 3 types of angle measuring instrument.

    (I)Sine bar                   (II)Clinometer     (III)Bevel Protector

                    

   SINE BAR:-

→sine bar is an angle-measuring instrument that measures slope of any object with the help of slip gases and a dial indicator.

→it is a steel piece mounted over two hardened steel cylindrical roller having equal diameter.

→To make it lighter in weight small holes are drilled along steel piece.

Principle:-

→The working of sine bar is based on the princiople of trigonometry. 

In this one roller is placed over combination of slip gauges and another is placed over table surfaces.

→If H is the height of slip gauge combination and L is the center distance between two rollers.

Then,

          Sinθ =  (h / L). 

           θ = sin^-1 (h / L).

          θ = Slope of object surface.

Working:-

→First place the object whose surface inclination is to be measured over the flat surface of sine bar.

→Make combination of slip gauges such that inclined surface of workpiece or object becomes parallel to ground.

→Place one cylinderical roller over slip gauges&one over table surface.

→Move the dial indicator over workpiece surface to ensure the workpiece inclined surface becomes parallel to ground .

→If there is deviation in dial indicator then re-arrange the slip gauge till deviation eliminates.

→Then calculate,

                          θ = sin^-1 (h / L).

→It can measure inclination upto 45°

→Accuracy of sine bar is upto 0.01mm/m of length.        

  Clinometer:-

→ It is an angle measuring instrument.

→It consists of one plate known as base plate

→It has a pointer which is so arranged that it is always parallel to ground.

→Pointer contains a spirit level having ethanol present in it in form of bubble.

→It has a scale of degree and the whole unit is enclosed in a casing known as housing.

Working principle of clinometer:-

→The base plate is placed over work piece whose inclination is to be measured.

→Now the pointer deflect as it always tends to become parallel to ground.

→During movement of pointer bubble in  spirit level vibrates but when pointer becomes parallel to ground bubble stops vibrating and comes at its center.

→When bubble comes at center, reading of pointer on a scale gives reading of inclination of surface.

        UNIVERSAL BEVAL PROTECTOR:-

→ Bevel protector is the simplest instrument for measurement of angle.

→ It consists of main circular plate arranged on adjuststable blade 

→Fixed blade carries a circular plate with vernier scale

→ Main plate can swivel inside the circular plate main plate has reading from 0-90-0.

→Vernier scale has 24 division and each division=5 min....

WORKING PRINCIPLE:-

→The base plate/fixed blade concides with workpiece one surface so that adjustable blade concides with surface whose angle is to be measured.

→Due to this main plate swivelled and thus reading is obtained.

→ Reading will be sum of main scale reading and vernier scale reading

i.e.,Total reading=Main scale reading+vernier scale reading.

→For main scale reading "0" of vernier concide with main scale marking.

→For vernier scale reading marking of vernier scale reading concide with marking of makin acle.