Method and control circuit for regulating pressure by means of solenoid valves, e.g. for pressure testing of plastic tubes

摘要

In order to be able to ensure even close tolerances for the maintenance of the test pressure, uniformly long control pulses are not used for the solenoid valves (MV1), but rather, after the first determination of a pressure deviation, a first control pulse (MV1OUT) having a prescribed initial duration is triggered for the solenoid valve (MV1) to be controlled, and in the case of each pressure deviation subsequently measured at periodic intervals, a further control pulse becomes effective, the pulse duration of each subsequent control pulse being lengthened by a prescribed time duration with respect to the respective preceding pulse. Generation of the sequences of control pulses by separate solenoid valve control units, irrespective of the commands of a superordinate control unit in the case of undershooting and overshooting of a prescribed switching threshold PU1 and PO1, respectively. IMAGE