pls suggest some good books for studying about flowmeters and control systems

 

There's numerous instrumentation/control text books, like Process Control Instrumentation Technology by Curtis D. Johnson, that can be had for pennies on the dollar from used book sites.

Note that this title in about its 8th or 9th edition. Flow technologies cover about 6 pages of 700, but it has the basics of control. Other texts have more on flow technologies.

Then there are the standard references, the "fat" books:

Flow Measurement: Practical Guides for Measurement and Control by David W. Spitzer, published by ISA. It's the first one I look to. My copy is 1991, I'm sure there's been at least one, if not two later editions.

Flow Measurement Engineering Handbook by Richard W. Miller. Again, my copy is 1983 and I know there are several more recenteditions.

Instrumentation Reference Book by Walt Boyes has a comprehensive review of flow technologies

I don't have a copy of Flow Measurement by Bela G. Liptak, so I'm not sure how different it is from his Instrumentation Engineers Handbook: Process - 3 different volumes, 1-measurement, 2-control, 3-software & networks.