One minor point to add to Artsupremo's answer. Valves can be either air to open or air to close. With one you start with the valve closed and the other with the valve open. The procedure is the same for both types of valves, I just wanted to clarify that point.
For any pnuematic control valve the operating pressure is from 3 to fully opened at 15 psig. It means a pnuematic control valve opens fully at 15 psi and closes at 3 psig. To calibrate it,prepare the following, one mercury manometer 0 tp 1000mm,Hg, one air pressure regulator for 20psig supply and air hoses,3 to15 psi output gauge, micrometer screw pressure regulator and air pressure supply. Prepare a Tee with the air supply at the center.Connect one leg to the mercury manometer and the other equalizer leg to the control valve and a tee on top of the valve and an output gauge connected to the tee.. Both the manometer and control valve should receive equal pressure from the pressure regulator. A 15psig pressure is 775 mm mercury . So, set the mercury manometer to an equivalent of 15 psig,775mmHg, and prepare a table of equivalent pressure from 3, 6, 9, 12 and 15psig. The valve should be fifty percent open at 9 psig and 25% open at 6 psig, likewise, it should close at 3 psig and 75% open at 12 psig fully opened at 15 psig. The pressure variation may be done with the micrometer type pressure regulator at the pressure supply.
