What are Differences between indenter of vickers and knoop

Hello Pals,
  
Vickers and Knoop both are micro indentation hardness testes. There are differences in indenter and load used in these tests even if tests can be done on same machine. Let’s see what they are.

Differences between Vickers & Knoop indenter:

Simplest explanation for differences

 Vickers - Pyramidal shaped diamond indenter
Knoop- Rhombohedral shaped diamond indenter

Differences in shape of indenter  >>Differences in measurement of impression.

 What more Differences in Indenter?

Vickers indenter is pyramidal shape with an angle of 136° between opposite faces.
Knoop indenter is rhombohedral shape with an included longitudinal angle of 172° 30′ and an included transverse angle of 130° 0′.

 In  Vickers test hardness calculations are based on mean of measurements of two diagonals of impression.in Knoop hardness calculations are based on measurement of long diagonal of impression.