• A tachometer : is an instrument that measures the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute (RPM) on a calibrated analog dial, but digital displays are increasingly common.
this part is used in cnc machines and some of the other conventional machines for measuring the speed of the motor and controlling the speed of it in the cnc machines.
• its operation :
it depends on cutting the magntic field induced between coils then it goes to the circuit that transmits the signal into volts then to a reading to a machine
Enchoder : its used to determine the displacement of the axis in the conventional machines and controlling them in the cnc machines.
• Its operation : it has a circular ruler depends on the optic technology
That when the light fall in the space between the ruler and transfere it through the voltage circuit to digital output
figure (4.1 ) enchoder
photo cell working through varying resistance across it according to intensity of light hitting the surface
figure 4.2 photo cell