Patent ID: 7684768

Claim:
A self-powered current loop transmitter for transmitting a process variable over a wireless link including in combination: a micro-controller having an analog input, a process output, and a control output; first and second input terminals adapted for connection to an external current source; a unidirectional current flow device, a voltage regulator, and a monitoring resistor, connected in series circuit, in the order named, between the first and second input terminals, with the connection between the unidirectional current flow device and the voltage regulator comprising a first junction and the connection between the voltage regulator and the monitoring resistor comprising a second junction; a switch device and a storage capacitor connected in series circuit, in the order named, between the first junction and the second input terminal, with the connection between the switch device and the storage capacitor comprising a third junction connected to the micro-controller to supply operating power thereto; a reference resistor and a Zener diode connected in series circuit, in the order named, between the third junction and the second input terminal to supply a reference voltage to the micro-controller at a fourth junction between the reference resistor and the Zener diode; a connection between the second junction and the analog input to the micro-controller; a connection from the control output of the micro-controller to the switch device to cause the switch device to open and close the circuit from the unidirectional control device to the storage capacitor; and a transmitter, supplied with operating power from the third junction, coupled with the process output of the micro-controller for transmitting converted process data from the micro-controller.