| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce the burden of an operator and to improve the reliability and safety of relation control by not starting a manual operation but continuing automatic control when abnormality is caused at any one of two detectors and the difference of detecting signals between them is small. SOLUTION: A switcher 3 selects one of detecting signals outputted from detectors 1 and 2 and sends it to a control part. At a switching permission discrimination circuit 20, a subtracter 21 always comparatively subtracts the respective detecting signals of the detectors 1 and 2, the subtracted value is inputted through a dead time delay element 23 to an upper/lower comparison limit detector 25 and when the subtracted value is settled within a prescribed set range, a switching permit signal E is outputted. Then, when the switching permit signal E is turned on and a detector abnormal signal B concerning the detector 1 is outputted while the detecting signal of the detector 1 is selected, a signal establisher 17 outputs a switching signal A and inputs it to the switcher 3. Therefore, the switcher 3 selects the detecting signal of the detector 2 and automatic control is continued.</p> |
