Patent ID: 7293470

Claim:
A two-wire bus instrument ( 500 ) adapted for use with a two-wire bus ( 308 ), comprising an instrument element ( 304 ) that receives a third current and that generates one or more sensor measurement signals, a signal processor ( 512 ) that receives a second current and that processes the one or more sensor measurement signals from the instrument element ( 304 ) to produce a data signal, and a communication system ( 511 ) that receives a first current and that receives the data signal from the signal processor ( 512 ), generates a digital communication signal including the data signal, and modulates the digital communication signal onto the two-wire bus ( 308 ); wherein the two-wire bus instrument ( 500 ) is further characterized by: a communication power supply ( 501 ) connected to the communication system ( 511 ) and wherein the communication power supply ( 501 ) and the communication system ( 511 ) are capable of being connected across the two-wire bus ( 308 ), with the communication power supply ( 501 ) being configured to provide the first current, a substantially constant voltage, and a first power to the communication system ( 511 ); a signal processing power supply ( 502 ) connected to the signal processor ( 512 ) and wherein the signal processor ( 512 ) and the signal processing power supply ( 502 ) are capable of being connected across the two-wire bus ( 308 ) and in parallel with the communication power supply ( 501 ) and the communication system ( 511 ), with the signal processing power supply ( 502 ) being configured to provide the second current, a substantially constant voltage, and a second power to the signal processor ( 512 ); a drive current power supply ( 503 ) connected to the instrument element ( 304 ) and wherein the instrument element ( 304 ) and the drive current power supply ( 503 ) are capable of being connected across the two-wire bus ( 308 ) and in parallel with the communication power supply ( 501 ) and the communication system ( 511 ) and further in parallel with the signal processing power supply ( 502 ) and the signal processor ( 512 ), with the drive current power supply ( 503 ) being configured to provide the third current, a substantially constant voltage, and a third power to the instrument element ( 304 ).