Trumeter apm voltagecurrentfrequency panel meters 4 digit analog bar graph trumeter apm freq apn the trumeter apm apm freq apn programmable lcd panel frequency meter features a 4 digit numeric display for precision and a 40 segment curved bargraph to show dynamic circuit conditions simply plug the meter into your pc via usb and use the free software to alter key parameters such as the scale of the bar graph alarm set points and the background colour of the meter face a 16 position switc