gas safety device 1)Unit:ppm, mA, %,%LEL,%VOL 2)Display:backlight LCD, LED 3)Humidity: 10-95%RH (non condensing ... * 4-20mA, 2 wire connection ,compatible with existing alarm control unit or DCS (Distributed Control System) * Flameproof body design acc. ... ,simple and easy installation and maintenance. * Multi-parameter backlight LCD display: measuring range,digital gas reading ,units, bar graph , system ...