This video is of an early pressure balancing test and was recorded in the Equilibar engineering laboratory. Subsequent testing has shown that superior pressure balance across the membrane can be achieved with minor modifications. In the video, two Equilibar precision back pressure regulators (BPRs) are operated with a common pilot pressure. The pilot consists of a small volume chamber that is opened to the atmosphere through a small bleed orifice. The size of the bleed orifice controls the rate at which the pilot pressure drops. One of the Equilibar BPRs controls the simulated oxygen pressure, while the second Equilibar BPR controls the simulated hydrogen side pressure of the electrolyzer membrane. Since compressed air was used as the media in the testing, the tank volume representing oxygen is roughly five times that of the tank volume representing hydrogen. A differential pressure (DP) transmitter is connected between the two volumes. A standard gauge pressure transmitter is connected to the pilot pressure chamber to track the pressure decay rate through the bleed orifice. To start the process, a valve is opened that allows the orifice to begin bleeding the pilot air volume into the atmosphere. This system is all mechanical, and no closed-loop electronics are used. Tight control of the differential pressure across an electrolyzer membrane prevents the crossflow and mixing of gases and prevents mechanical damage to the electrolyzer membrane.