Trumeter apm ct meters with lcd display trumeter apm ct apo this apm ct meter from trumeter has been designed to use with an external current transformer for accurately measuring up to 10 000 amps the meter is equipped with a host of excellent features including the dynamic backlighting and high resolution input in conjunction with set points meaning operators are visually alerted when a parameter is out of range while the programmable scale and custom annunciators allows users to tailor