Additel ADT 901A Low Pressure Test Pump is a hand operated pressure pump designed to generate pressures from -6 psi (-0.4 bar) to 6 psi (0.4 bar). A high-quality screw press is designed for fine pressure adjustment, with an adjustment resolution up to 0.01 Pa (0.0001 mbar). To reach the pressure as stable as possible during micro-pressure calibrations, an isothermal bellows chamber is designed for reducing the possible heat effects caused by environmental temperature change. Without non-returning valve that is usually used on troublesome hand pumps, the ADT 901A requires minimal maintenance. Two hand-tight connectors installed on the pump allow easy connecting and disconnecting to the test pump without the need for PTFE tape or wrenches. The ADT 901A is an ideal comparison test pump for low pressure applications.