Pneumatic pressure transmitters transmit pressure signals to remote pneumatic receivers. Both blind and indicating transmitters are available. Blind transmitters are preferred because they use force-balance mechanisms (See Section 411). Accuracy should be within 0.5% of the calibrated span.
Pneumatic pressure transmitters should have weatherproof cases of fiberglass or aluminum. The pressure element should be compatible with the process pressure and fluid.
The transmitter should be designed to operate on an instrument air supply pressure of 18 to 22 psig. The output pressure should be 3 to 15 psig. Output is typically specified as direct acting, but reverse acting is an available option. The transmitter should have supply and output pressure gages. The process connection should be ½-inch female NPT. The case should include a socket or yoke for mounting on a 2-inch pipe.