Patent ID: 6928868

Claim:
An apparatus for monitoring a liquid level in a 4-20 mA closed loop system, comprising: a process instrument; a power source configured to generate power; a switching arrangement including an input coupled to the power source to receive power therefrom, the switching arrangement further including an output, the switching arrangement being configured to transmit power from the input to the output for a predetermined time; the switching arrangement further including a timing arrangement, the switching arrangement being configured to use the timing arrangement for controlling the predetermined time; and a measuring unit coupled to the output of the switching arrangement to receive power therefrom, the measuring unit being configured to transmit power to the process instrument and to receive a 4-20 mA signal therefrom, the measuring unit including an indicator being configured to be powered by the 4-20 mA signal and being further configured to indicate the liquid level based on the 4-20 mA signal.