| 摘要 |
PURPOSE:To decrease the generation of a fault by deciding in which direction a temperature detected value is varied, and in which area said value exists, at the time of variation of a load capacity, and executing ON/OFF operations before an operation at the time of a stationary load. CONSTITUTION:A temperature controller brings a final control element 15 to ON/OFF operations, based on an output of a temperature detector 14 in order to allow a steel plate 11 to be brought to a surface treatment, to pass through in a solution 13 in a treatment tank 12 and to execute stably the surface treatment of the steel plate, and controls said solution 13 to a prescribed temperature. In this case, a detected value PV of the temperature detector 14 is supplied to not only a deviation calculating part 17 but also a difference calculating part 18, and a variation rate signal is derived and supplied to lower limit/upper limit variation rate direction deciding circuits 19, 20. Subsequently, when its has exceeded the lower and the upper limits, a conditional signal for bringing the final control element 15 to ON/OFF operations is outputted. This signal is sent to negative/positive area deciding circuits 21-22, and when it is decided that the condition has been formed, said signal is set to a holding memory 27 from OR circuits 25-26. In such a way, a temperature can be controlled appropriately in spite of a change of a load capacity.
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