Speed measurement of Hydraulic cylinder

I am using hydraulic cylinder for a carriage movement which is controlled by servo valve. The distance moved by the cylinder was measured using linear potentiometer. Servo valve control and linear pot. was interfaced to S7-200 PLC and controlled.

The thing is by using the Linear pot. i want to measure the speed of the carriage movement instantaneously (approx for 200ms). Is there is standard Plc program for measuring the speed by Linear Potentiometer.

R. SathyaNarayanan