Ultrasonic sensor for Human Height measurement

We are looking for proximity/ distance measuring sensor for automated measurement of Human height for Medical purpose.

anybody can tell correct sensor to measure Human height ...........

I would suggest investigating a laser range finder/ruler as these have had the benefit of development for a mass market and are now low cost and robust. They are now routinely used for room measurements for house sales/marketing and the DIY industry.
Other possible options are the robotic distance measuring sensors such as produced by Sharp.
Ultrasonic could be used, but you may find temperature affects are an issue and you need to measure the ambient temp and apply a correction factor.

Key things you need to consider are 'how you want to do the measurement'.
Will the subject stand on a platform similar to being weighed.
Will you still move a flat surface down to the top of the head as with a ruler system. Etc.

Another are is whether a fixed camera(s) arrangement could be used and a triangulation system applied to the image. Obviously the subject needs to be at a fixed position from the camera (or a known distance) and you will have to devlop the imaging software if this does not already exist.