Field-mounted control unit

A smart field-mounted control unit for coupling to a two wire DC current process control circuit which carries a loop current, the two wire circuit electrically connected in series with a power source, a remote device and the control unit, the control unit comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry adapted to receive power from the power source through the two wire circuit which wholly powers the control unit and adapted to receive a setpoint from the two wire circuit;
• a process variable sensor which provides a sensed process variable;
• and
• control circuitry in the housing operably coupled to the input circuitry, the process variable sensor, and the two wire circuit whereby the control unit is adapted to be electrically connected in series with the two wire circuit and the control circuitry provides a command output for the two wire circuit as a function of the setpoint and which is a function of a previous value of the command output.

A smart field-mounted control unit for coupling to a two wire circuit, comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry adapted to receive power from the two wire circuit for wholly powering the control unit;
• a process variable sensor which provides a sensed process variable;
• and
• control circuitry in the housing operably coupled to the input circuitry and to the process variable sensor, the control circuitry is adapted to provide a command output for a remote device, the command output in a digital format which is a function of the sensed process variable and a previous value of the command output.

A smart field-mounted control unit for coupling to a two wire circuit for controlling a process control loop, comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry receiving power from the two wire circuit for wholly powering the control unit and the input circuitry adapted to receive a command from the two wire circuit;
• a process variable sensor which provides a sensed process variable;
• control circuitry in the housing operably coupled to the input circuitry and to the process variable sensor and including at least one instruction set, wherein the control circuitry selects the instruction set in response to the command for providing a command output for a remote device as a function of the sensed process variable.

A smart field-mounted control unit for coupling to a two wire circuit, comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry receiving power from the two wire circuit for wholly powering the control unit and the input circuitry receiving a process signal from the two wire circuit representative of a process variable;
• and
• control circuitry in the housing operably coupled to the input circuitry, the control circuitry provides a command output to a remote device, the command output in a digital format which is a function of the process variable and a previous value of the command output.

A smart field-mounted control unit for coupling to a two wire circuit for controlling a process control loop, comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry receiving power from the two wire circuit for wholly powering the control unit and the input circuitry adapted to receive a command and a process variable from the two wire circuit;
• and
• control circuitry in the housing operably coupled to the input circuitry and including at least one instruction set, wherein the control circuitry selects the instruction set in response to the command for providing a command output for a remote device as a function of the process variable.

A transmitter adapted for use in a conventional process control two wire circuit in which a parameter is represented by a 4-20 mA DC current in the two wire circuit and the transmitter is solely powered by such current, the transmitter comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit for receiving a first signal from the two wire circuit;
• a process sensor in the housing adapted to couple to a process and sense a process variable to produce a second signal which is representative of the process;
• and
• control circuitry in the housing coupled to the input circuitry and the process sensor, the control circuitry adapted to provide a command output for a remote device as a function of the first signal and the second signal, wherein the command output is representative of a control signal which is the parameter.

A smart field-mounted control unit for coupling to a two wire DC current process control circuit which carries a loop current, the two wire circuit electrically connected in series with a power source, a remote device and the control unit, the control unit comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry adapted to receive power from the power source through the two wire circuit which wholly powers the control unit and adapted to receive a setpoint from the two wire circuit;
• a process variable sensor which provides a sensed process variable;
• control circuitry in the housing operably coupled to the input circuitry, the process variable sensor, and the two wire circuit whereby the control unit is adapted to be electrically connected in series with the two wire circuit and the control circuitry provides a command output for the two wire circuit as a function of the setpoint;
• and
• wherein the input circuitry is further adapted to receive a command from the two wire circuit which selects an instruction set stored in the control unit.

A smart field-mounted control unit for coupling to a two wire DC current process control circuit which carries a loop current, the two wire circuit electrically connected in series with a power source, a remote device and the control unit, the control unit comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry adapted to receive power from the power source through the two wire circuit which wholly powers the control unit and adapted to receive a setpoint from the two wire circuit;
• a process variable sensor which provides a sensed process variable;
• control circuitry in the housing operably coupled to the input circuitry, the process variable sensor, and the two wire circuit whereby the control unit is adapted to be electrically connected in series with the two wire circuit and the control circuitry provides a command output for the two wire circuit as a function of the setpoint;
• and
• wherein the input circuitry is further adapted to receive from the two wire circuit a coefficient of a term of an instruction set stored in the control unit.

A smart field-mounted control unit for coupling to a two wire DC current process control circuit which carries a loop current, the two wire circuit electrically connected in series with a power source, a remote device and the control unit, the control unit comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry adapted to receive power from the power source through the two wire circuit which wholly powers the control unit and adapted to receive a setpoint from the two wire circuit;
• a process variable sensor which provides a sensed process variable;
• control circuitry in the housing operably coupled to the input circuitry, the process variable sensor, and the two wire circuit whereby the control unit is adapted to be electrically connected in series with the two wire circuit and the control circuitry provides a command output for the two wire circuit as a function of the setpoint;
• and
• wherein the control circuitry is adapted to provide a digital signal for the two wire circuit representative of a serial number of the control unit.

A smart field-mounted control unit for coupling to a two wire DC current process control circuit which carries a loop current, the two wire circuit electrically connected in series with a power source, a remote device and the control unit, the control unit comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry adapted to receive power from the power source through the two wire circuit which wholly powers the control unit and adapted to receive a setpoint from the two wire circuit;
• a process variable sensor which provides a sensed process variable;
• control circuitry in the housing operably coupled to the input circuitry, the process variable sensor, and the two wire circuit whereby the control unit is adapted to be electrically connected in series with the two wire circuit and the control circuitry provides a command output for the two wire circuit as a function of the setpoint;
• and
• wherein the function further comprises a PI function.

A smart field-mounted control unit for coupling to a two wire DC current process control circuit which carries a loop current, the two wire circuit electrically connected in series with a power source, a remote device and the control unit, the control unit comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry adapted to receive power from the power source through the two wire circuit which wholly powers the control unit and adapted to receive a setpoint from the two wire circuit;
• a process variable sensor which provides a sensed process variable;
• control circuitry in the housing operably coupled to the input circuitry, the process variable sensor, and the two wire circuit whereby the control unit is adapted to be electrically connected in series with the two wire circuit and the control circuitry provides a command output for the two wire circuit as a function of the setpoint;
• and
• wherein the function further comprises a PD function.

A smart field-mounted control unit for coupling to a two wire DC current process control circuit which carries a loop current, the two wire circuit electrically connected in series with a power source, a remote device and the control unit, the control unit comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry adapted to receive power from the power source through the two wire circuit which wholly powers the control unit and adapted to receive a setpoint from the two wire circuit;
• a process variable sensor which provides a sensed process variable;
• control circuitry in the housing operably coupled to the input circuitry, the process variable sensor, and the two wire circuit whereby the control unit is adapted to be electrically connected in series with the two wire circuit and the control circuitry provides a command output for the two wire circuit as a function of the setpoint;
• and
• wherein the function further comprises a PID function.

A smart field-mounted control unit for coupling to a two wire DC current process control circuit which carries a loop current, the two wire circuit electrically connected in series with a power source, a remote device and the control unit, the control unit comprising:

• a housing;
• input circuitry in the housing adapted to be operably coupled to the two wire circuit, the input circuitry adapted to receive power from the power source through the two wire circuit which wholly powers the control unit and adapted to receive a setpoint from the two wire circuit;
• a process variable sensor which provides a sensed process variable;
• control circuitry in the housing operably coupled to the input circuitry, the process variable sensor, and the two wire circuit whereby the control unit is adapted to be electrically connected in series with the two wire circuit and the control circuitry provides a command output for the two wire circuit as a function of the setpoint;
• wherein the command output is further a function of a difference between the setpoint and the sensed process variable.