hi guyz i am using a dc motor with a encoder.......the problem is i have no details about the motor nor the encoder there is no part no on it
Q1) how do i calculate that how many pulses the encoder has?
You can't because you don't know what scheme the encoder is using.
Q2) what is the gear ratio of the motor ?
The only way to know is if the shaft can be rotated from one end and the rotations counted on the output end. Some you can and some you can't.
Q3) i am a bit confused about servo motor..............if a dc motor has a encoder feedback on it can we call it a servo motor?
The first servomotors were developed with synchros as their encoders. Much work was done with these systems in the development of radar and anti-aircraft artillery during World War II.
Simple servomotors may use resistive potentiometers as their position encoder. These are only used at the very simplest and cheapest level, and are in close competition with stepper motors. They suffer from wear and electrical noise in the potentiometer track. Although it would be possible to electrically differentiate their position signal to obtain a speed signal, PID controllers that can make use of such a speed signal generally warrant a more precise encoder.
Modern servomotors use optical encoders, either absolute or incremental. Absolute encoders can determine their position at power-on, but are more complicated and expensive. Incremental encoders are simpler, cheaper and work at faster speeds. Incremental systems, like stepper motors, often combine their inherent ability to measure intervals of rotation with a simple zero-position sensor to set their position at start-up.
Instead of servomotors, sometimes a motor with a separate, external linear encoder is used.[4] These motor + linear encoder systems avoid inaccuracies in the drivetrain between the motor and linear carriage, but their design is made more complicated as they are no longer a pre-packaged factory-made system.
They are not all called Servo Motors. A Stepper Motor can also have feedback. All the feedback is doing is telling us where the motor is position wise. The above for Q3 taken from the WIKI.