Used in a wide application for air conditioning, combustion process control, ventilation and clean rooms monitoring, pressure transmitters are especially designed for low and very low pressure differences measuring. They can measure both positive and negative pressure differences as well as overpressure and underpressure against ambient atmosphere. The unit has a small additional solenoid valve which an internal program controls. Periodically the valve disconnects the pressure inputs of the pressure sensor for a 300 ms period which is when offset correction is measured and recalculated. Self zeroing period can be set from 10 minutes up to 256 hours or can be switched-off.The transmitters have a nominal pressure range of +/- 50 Pa to +/- 3 kPa. Overpressure is 20 kPa and common mode pressure is 10xPdif, max. 20kPa.