| 摘要 |
<p>A control device for a vacuum pump apparatus in which a hunting effect is substantially eliminated. A pressure-sensitive switch senses a negative pressure produced by a vacuum pump, the latter being driven by a d.c. motor. The switch has at least three contacts, the positions of which are changed at two different pressures. The output of the switch is compared with a fixed reference value, and the comparison result used to drive the d.c. motor. The d.c. motor is thus provided with hysteretic drive characteristic, thereby maintaining the vacuum pressure between the two predetermined values and eliminating the hunting effect.</p> |
