| 摘要 |
A microcomputer-based programmable control system for desiccant air dryers monitors the level of moisture saturation of the desiccant beds and adjusts the regeneration cycle accordingly to optimize energy efficiency. The moisture sensors have capacitance probes and adjustable resistors as frequency determining components for precision oscillators. A multiple counter integrated circuit is controlled by the microcomputer to establish a predetermined time interval and to count cycles of the precision oscillators during the predetermined time interval to obtain final counts for each probe indicative of the level of moisture saturation in the respective desiccant beds. The microcomputer compares the final counts to predetermined threshold number in order to determine whether a regeneration cycle is required, and also compares the final counts to maximum and minimum threshold numbers to detect and indicate probe failure. A pair of high and low pressure sensitive switches is provided for each desiccant bed, and the microcomputer tests for coincidence of the high switches and the low switches to monitor full depressurization and repressurization of the regenerating bed and to analyze and indicate valve malfunction. The control system directly activates low current, low capacity solenoid valves which in turn operate high pressure pneumatic relays to drive the valves in the air dryer. |
