Patent ID: 8477064

Claim:
A loop-powered field device for determining a process variable and providing a measurement signal indicative of said process variable to a remote location via a two-wire current loop, said loop-powered field device comprising: a measurement device for determining said process variable; and loop interface circuitry for providing said measurement signal to the two-wire current loop and for providing power from said two-wire current loop to said measurement device, wherein said loop interface circuitry comprises: current control circuitry connected to the two-wire current loop and the measurement device, said current control circuitry being controllable by said measurement device to provide said measurement signal to the two-wire current loop; a first converter having inputs connected to said two-wire current loop in series with said current control circuitry, and an output for providing power to said measurement device; and voltage regulation circuitry for regulating a voltage across said current control circuitry towards a desired voltage, by controlling an input voltage across the inputs of the first converter.