| 摘要 |
<p>PURPOSE:To make it possible to succeed the control of a dissolved oxygen amount by a method wherein an auxiliary dissolved oxygen meter is provided in the vicinity of an inflow port of an aeration tank as well as a main dissolved oxygen meter in the vicinity of an outflow port thereof to reply the change of an inflowed sewage rapidly and, thereby, DO is controlled constantly as well as a signal switching function is imparted. CONSTITUTION:When a main DO meter 22 and an auxiliary DO meter 21 are in a normal condition together, the output of the main DO meter 22 is applied to a DO adjustment meter 3 as well as a field forward amount of an operation control circuit 23 is added to an MV value of the DO adjustment meter 3 by an operator 24 to control an air amount supplied to an aeration tank 1. Moreover, when the main DO meter 22 is abnormal, a sensor check circuit 33 detects this condition and the input to the DO adjustment meter 3 is switched to the auxiliary DO meter 21 smoothly by a bumpless circuit 32 as well as the connection of an operation control circuit 23 and an accumulator 24 is interrupted to succeed the control of an air amount supplied to the aeration tank 1 by the control operation only according to the auxiliary DO meter 21.</p> |
