| 摘要 |
PURPOSE:To attain the early detection of an abnormality, etc., of a control system by measuring the valve aperture of a needle valve so as to generate an alarm, if it deviate from a preset valve aperture. CONSTITUTION:Gas whose flow quantity is to be measured runs through a piping 1 in the direction of arrows, while its mass flow is measured by a censor 2. Also the control of the flow quantity is made by the top and the bottom parts of a needle valve 3. A comparison control circuit 7 will compare a value measured by the flow quantity censor 2 with a preset value, send a signal to a stepping motor 4 so that they may be equal, and thereby change the valve aperture. When the range of the valve aperture is preset in a valve aperture alarm 9, a valve aperture indication deviated from such a range will result in the generation of an alarm. |
