how to measure screw gauge and vernier callipers and beam balance

Dear student 

Steps of measurement of thickness of steel sheet with Vernier callipers:
Note the zero error of the vernier callipers without placing any object between the jaws of the vernier callipers.
Place the steel sheet in between the jaws and push the jaws firmly until the steel sheet is held tightly between the jaws.
Note the main scale reading which is coinciding with zero of vernier scale.
Note the vernier coincidence with main scale.
The thickness of the steel sheet is measured by using the following formula:
             Thickness of steel sheet = MSR + (Vernier coincidence) (Least count) ±± zero error correction

Note: If the zero error is positive, then the correction is negative and vice versa.