FA 400 is a absolute humidity sensor for dryers produced by Festo, Germany. It has four measurement ranges: -80.20°Ctd, -60.30°Ctd, -20.50°Ctd and 0.100%rF, with accuracies of ± 1°C, ± 2°C, ± 3°C respectively. The pressure range is -1.50 bar, and a special version can reach 350 bar. It can be connected to power and alarm lines via 2 x M12, 5-polig ports, and supports SDI interface. It provides 4.20 mA analog output with a maximum load of 500 Ohm. The alarm relay can output a maximum of 60 VDC, 0.5 A. It is suitable for cold dryers, membrane dryers and adsorption dryers.