Analog current / digital bus protocol converter circuit

A protocol conversion device for use in a control system comprising:

• an input circuit for receiving a Fieldbus compliant digital signal;
• a first system converting the Fieldbus compliant digital signal into an analog output signal having a current in the range of 4-20 mA;
• and
• a connecting system coupling the first system to an analog control device.

A converter circuit capable of converting analog output signals of at least two sensor transmitters into digital signals comprising:

• an input circuit coupled to at least two sensor transmitters and including:
• I. a multiplexer having at least two inputs and one output, the inputs of the multiplexer receiving analog output signals from each of the sensor transmitters, the multiplexer selecting one of the sensor transmitters such that the analog output signal from the selected sensor transmitter is coupled to the output of the multiplexer, and
• ii. an analog-to-digital converter coupled to the output of the multiplexer, the analog-to-digital converter converting one of the analog output signals that is present at the output of the multiplexer into a corresponding digital signal;
• and
• a main circuit coupled to the input circuit and including:
• I. a central processing unit coupled to the analog-to-digital converter and to the multiplexer, the central processing unit controllably selecting the analog output signal from the selected sensor transmitter and converting the digital signal from the analog-to-digital converter to a digital quantity of a property of interest from the selected sensor transmitter, and
• ii. a local adjust coupled to the central processing unit, the local adjust allowing a user to input conversion parameters for operating the central processing unit and displaying an operation criteria of a display controller into the central processing unit.

A converter circuit capable of converting analog signals of at least two sensor transmitters into digital signals and capable of converting the digital signals into the analog signals, the converter circuit comprising:

• an input circuit coupled to at least two sensor transmitters and including:
• a first system receiving and dispatching the analog signals via each of the sensor transmitter and selecting one of the sensor transmitters such that the analog signal from the selected sensor transmitter is coupled to the output of the first system,
• a second system converting one of the analog signals appearing at the output of the first system into a digital signal, and
• a third system converting one of the digital signals into a corresponding analog signal;
• a main circuit coupled to the input circuit and including:
• a control system selectably controlling the analog signal from the selected sensor transmitter and one of the digital signals, the control system converting the digital signal from the the second system in the input circuit to a digital quantity of a property of interest from the selected sensor transmitter;
• a display system displaying the digital quantity;
• and
• a fourth system receiving the digital quantity of the property of interest from the first system of the main circuit and formatting the digital quantity for the display system, the fourth system coupled to the third system and receiving the digital signals.