Bubble flow detection

A fluid flow detection method is used in a continuous ink jet printer which generates a row of parallel selectively charged drop streams from a fluid system. In the fluid flow detection method, a low airflow catcher device is provided for establishing bubble flow in an associated catcher vacuum port and catcher return line. The catcher return line contains catcher return fluid. Pressure fluctuations are monitored in the catcher return fluid to the ink tank, the ink tank having a tank vacuum. The tank vacuum is automatically lowered to a preset value, which preset value is greater than bubble flow transition. The tank vacuum is then incrementally lowered as pressure fluctuations are monitored. The tank vacuum is maintained at a constant level when the pressure fluctuations decrease below a predetermined level due to the establishment of bubble flow. Finally, the fluid flow detection method requires increasing the tank vacuum by a predetermined increment and maintaining that tank vacuum as the operating point for bubble flow for the printer.