PURPOSE: To ensure the detection of abnormality in the measured capacity level signal automatically, by comparing the added value of the integrated value of the deviation betwee the amount of an incoming flow and the amount of an outgoing flow and a holding value with the measued value at that point, and judging the abnormality when the result exceeds a specified preset value.
CONSTITUTION: A hold circuit 12 is operated. A measured level signal L(t) from a level measuring device is stored and maintained in the hold circuit 12. The amount of an incoming flow Qi(t) and the amount of an outgoing flow Qo(t) in a buffer container are measured by a measuring device. The difference ΔQ(t) between the amounts is computed by a subtractor 8. Let the capacity change in the buffer container be ΔQH(t). Then the ΔQH(t) is integrated for a specified time period from the time the measuring is started in an integrator 10. The result is divided by a sectional area S of the buffer container. Then the changing increment ΔH(t) of the level in the container is computed. In an adder 11, the value ΔH(t) and a holding value Ls, which is held by the holding circuit 12 when the measuring is started, are added, and an estimated value L'(t) of the level in the buffer container is obtained. In a subtractor 3, subtraction is performed between the measured value L(t), which is obtained by the measuring device at the time, and the estimated value L'(t). When a difference exceeds a preset range x, an abnormal signal is outputted.
SEKIGUCHI TETSUO
HIRABAYASHI SATORU
