Air sampling pump

摘要

A microprocessor controlled air sampling pump utilizes a PWM controlled DC electric motor for regulating air flow generated by a diaphragm-type air pump. The control system regulates air flow as a function of RPM of the motor by establishing a table of values which relate motor RPM to air flow rates. The control system maintains RPM at the desired value but includes a control loop which senses deviations in RPM and adjusts the PWM signals to the motor to regulate RPM. The system also senses large changes in RPM and treats such changes as blockages in the air sampling pump lines which prevent accurate environmental sampling. This system enters a cycling mode which turns the pump motor off for different time intervals until the detected blockage has been removed or until a predetermined time has expired. This procedure minimizes battery drain in the event of blockage of the air sampling pump lines. It also provides a method of accurately monitoring pump run time since it shuts off the pump during times in which the air flow is blocked.