Sigma Series DE Panel Meter. These Sigma Series of DE moving iron panel meters are housed in moulded polycarbonate cases and are suitable for the measurement of AC currents for a frequency range of 15-400Hz and voltages in the frequency range of 15-100Hz. Available in variety of sizes for both Ammeters ; Voltmeters Scale interchangeability Near linear scale Glass filled polycarbonate housing Knife edge pointer Easily replace able glass and bezel