Abstract: A modular transmitter has an outer housing with a wall forming an interior cavity in which a control module is inserted. The wall has one or more ports therein that are connected to pressure conduits. When the control module is fully seated, the ports align with internal passageways in the control module that lead to control components in the control module. The control module further has an electrical circuit supported on an end thereof that is toward the inner end of the cavity when the control module is inserted and the circuit has components that removably mate with further elements mounted on the end wall of the cavity. These connections may include electrical contacts, and also rotationally adjustable components that have set points and which are coupled to set point adjustment and control shafts that are accessible from the opposite side of the end wall from the cavity.

Abstract: A current-to-pressure (I/P) converter provides an output pressure as a function of the magnitude of a variable input DC current. The I/P converter includes a pressure sensor which produces a feedback signal representative of the output pressure. Based upon the feedback signal and the magnitude of the input DC current, an electrical control signal is produced which controls a device for varying the output pressure. The I/P converter also includes a circuit for generating a time-varying signal which is sent back over the current loop wires through which the input DC current flows. The time-varying signal provides an indication of whether the I/P converter is functioning properly. This permits diagnosis of possible causes of control system malfunctions without having to inspect the I/P converter itself.

Abstract: A fluid amplifier is used in a pneumatic transducer to provide a control output pressure in response to a pilot pressure provided as a function of a current signal. The fluid amplifier includes a valve that opens a pressure source to the control port and also controls pressure feeding through an exhaust passageway. The amplifier valve is provided with a negative feedback arrangement as the exhaust back pressure increases to stabilize the operation and make the amplifier less sensitive. The pneumatic amplifier is provided with a diaphragm arrangement that results in increasing exhaust back pressures tending to close the exhaust valve, rather than open the exhaust valve. The negative feedback makes the valve more easily controlled and provides for more stable operation.

Abstract: An improved magnetic actuator for providing mechanical actuation representative of an input current has a housing that supports a coil surrounding a central core, and includes a diaphragm type spring above the central core. A cover of high magnetic permeability is mounted on the housing spaced from the diaphragm spring. A permanent magnet is mounted on the diaphragm spring in a predetermined pole orientation and the magnet extends through an opening in the cover. The permanent magnet provides flux through the housing and the core. Sensitivity is increased by using the permanent magnet to provide a magnetic flux in addition to that created by currents in the coil.

Abstract: An electric signal to pneumatic signal transducer 10 comprises a nozzle 12 that accepts an input pneumatic supply and expels a gas stream 20. A receiver 16 that is spaced from the nozzle is positioned to recover at least a portion of the gas stream. The recovered portion constitutes a pneumatic output signal. The position of a deflector 14 relative to the gas stream is controlled by an electric input signal to aerodynamically deflect the gas stream expelled from the nozzle. The aerodynamic deflection affects the magnitude of the portion of the gas stream recovered by the receiver in a manner having a known relationship to the electric input signal, thereby generating a pneumatic output signal responsive to the electric input signal.