what is pnumatics and pneumatic controls

systems working on the application of air are called pneumatics.controllers in which air plays a role in deriving the various control action is called pneumatic controllers. ofcourse the air used is dry air suitable for instrumentation operation.

Mishra

thank u mishra sir thank for u r answer

You can see my explanation of "Air Logic Controls" used by some to replace Electric Relays or PLC's especially in Hazardous,Explosive atmospheres in Ch. 19 of a training book I use to teach Fluid Power here.

http://www.hydraulicspneumatics.com/200/eBooks/

Look at the Basic book for an explanation of different Logic Elements and in the Advanced book at Section 2 for several circuits using Air Logic. Air Logics is in Section 2 since that book is laid out alphabetically.

Usually , the output of a pneumatic instrument is 3 - 15 psi. 3 psi for 0% and 15psi for 100%.