Gicar Flow meters are the industry best. They are sensors that 'count' how much volume an automatic' espresso machine has dispensed.
Most machines take the standard 3 prong 'ungrounded' flow meter and a block connector is attached to the 3 prongs.
Some makers, namely Rancilio & Marzocco have the ground prong wired back to the flow meter body to ground it.
Flow meters are not voltage specific.