Just last year, digital panel meters (DPMs), counters/timers and barmeters required external power in the Watts range to display data to the operator (HMI), interface with computers (MMI) and measure a process variable such as the current loop. These processes inherently have their own energy (approximately 100 mW), produced by the 4-20 mA or V/mA transmitter. Most of this signal energy is wasted because most digitals require external power. The industry’s first current-loop-powered digital meter (before “green” existed) was designed around the concept of a barge going downstream using only the free energy of the flow of water.
This white paper explains the latest panel-meter technology that can take the energy of the singal's own power.