PRECISE PRESSURE CONTROL WITH OFF-ON VALVES AND FIXED VOLUME CHAMBERS

A system and method is described to precisely control the pressure in a sample chamber over a wide range of pressures. The system comprises a sample chamber connected to additional chambers via on-off valves. The volumes of these chambers are accurately pre-measured. The valves can be electronically controlled by a controller, such as a computer with a processor. Computer control of these valves to vary the pressures in the chambers to achieve a precise target pressure in the sample chamber is performed in a sequence of steps where the pressure in each chamber is calculated after each step, thereby eliminating the requirement of measuring the actual pressure in the chambers.