Field mounted control unit

A smart field-mounted control unit for controlling a process, communicating over a two-wire process control loop which powers the unit, comprising:

• a single enclosure;
• input means carried in the single enclosure coupled to the two-wire process control loop for receiving power over the two-wire process control loop, for receiving process signals over the two-wire process control loop from a master unit representative of more than one process variable, for sending information to the master unit over the two-wire process control loop, and for storing process signals;
• controlling means carried in the single enclosure coupled to the input means for providing a command output for controlling the process and for storing previous values of the command output, where the command output is a function of the stored process signals and a stored previous value of the command output;
• a source of energy capable of being regulated for controlling the process;
• and
• energy conversion means carried in the single enclosure coupled to the controlling means for regulating energy from the source and for applying the energy to the process as a function of the command output.

A smart field-mounted two-wire transmitter, comprising:

• a single enclosure;
• a sensing device carried in the single enclosure having means for sensing and scaling a first process variable;
• input means carried in the single enclosure coupled to a two-wire process control loop for receiving power over the two-wire process control loop, receiving process signals over the two-wire process control loop from a master unit, and for storing process signals;
• and
• controlling means carried in the single enclosure coupled to the sensing device and input means, for providing a command output to a remote device which controls a process and for storing the command output, where the command output is a function of the stored process signals, the scaled first process variable and a previously stored value of the command output.

An apparatus for improving a smart transmitter which is powered by a two-wire process control loop and which is coupled to and communicates with a remote device which controls a process, the transmitter having sensing means for sensing a first process variable, scaling means coupled to the sensing means for scaling the sensed process variable, communications means coupled to the scaling means for coupling the sensed process variable to the two-wire process control loop, characterized in that the apparatus comprises:

• a single enclosure;
• input means carried in the single enclosure for input and storage coupled to the two-wire process control loop for receiving process signals from a master unit over the two-wire process control loop, and for receiving power over the two-wire process control loop;
• and
• controlling means carried in the single enclosure coupled to the input means for providing a command output to the remote device and storing the command output, where the command output is a function of the process signals, the scaled process variable and a previously stored value of the command output.

A smart field-mounted transmitter powered by a first two-wire circuit and sending an output onto a second two-wire circuit, comprising:

• a single enclosure;
• a sensing device carried in the single enclosure having means for sensing and scaling a first process variable;
• input means carried in the single enclosure coupled to the first two-wire circuit for receiving other process variables from a master unit over the first two-wire circuit, for transmitting information to the master unit over the two-wire circuit, and storing the other process variables;
• compensation means carried in the single enclosure coupled to the input means for compensating one of the process variables as a function of the other process variables;
• and
• output means carried in the single enclosure coupled to the compensation means for coupling the compensated process variable to the second two-wire circuit.