preferably runs the psa cycle it will know when to acquire data from a common pressure sensor corresponding to which points in the cycle corresponds to peak product pressure in each bed or in the product storage vessel given the ability to measure peak pressure the operation of the beds may be compared as shown in fig3 a pressure vs time plot acquired for an exemplary psa cycle in the example the peak pressure in bed a is higher than the peak pressure in bed b indicating that the beds are not balanced if the beds are out of balance the efficiency of the concentrator decreases dramatically leading to lower device performance and reduced manufacturability with an arrangement as shown in fig2 with independent processor controlled valves the processor can adjust the valve timing to keep the beds balanced conversely the rate of purge can be adjusted if proportional valves are used in place of solenoid valves thereby not altering the step times but achieving the same net change in the volume of purge gas used to regenerate the adsorber this ability to detect and fix imbalance has two significant advantages first it allows for wider tolerances at manufacture thereby decreasing the cost of the concentrator and moreover as the concentrator is used in the field as a portable device aging effects and abuse can cause small leaks valve perturbations and so on which will cause bed imbalance the ability to monitor imbalance and make field adjustments can greatly extend the life of the concentrator moreover if the imbalance trend is monitored it may be possible to predict when service is needed before a failure causes the device to stop providing oxygen to a patient the.