The ACS730 has a 2.5 V output when measured current is zero, and is scaled for 40 mV/A. This gives an output voltage swing from -0.5 V for -50 A to +4.5 V for +50 A.

Most current meters used by scientists cost about $15,000 each, while Sheremet's meter is only about $500, and he makes each one by hand. It takes him about a week to build and calibrate 10 of them.