| 摘要 |
PURPOSE:To perform manual setting by using the same momentary switch as that used in normal operation even when processing by a microprocessor is impossible, and to improve responsiveness by providing a power source and a setting circuit for operation in case of abnormality occurrence. CONSTITUTION:Even when abnormality occurs to the microprocessor and a changeover switches 11 is changed over from the side of a terminal SM to the side of terminal HM, the terminal voltage of a capacitor 13 which holds the value right before that is supplied to a voltage-current converting circuit, so bumpless switching is performed without variation in signal value. When a switch 16 for an increase direction is turned on in said state, the signal value varies by resistances 18 and 12 and the capacitor 13 according to a first-order lag and a current output in an increase direction is obtained. When a switch 17 for a decrease direction is turned on, the signal value vaires negatively according to the first-order lag and a current output in the decrease direction is obtained. Therefore, the manual setting is possible over a look at a meter M by common momentary switches 17 and 18 regardless of whether the microprocessor is normal or not. |
