| 摘要 |
A level control system includes an upper chassis 4 supported on a lower chassis 2 by three screwthreaded drive rods 6 each driven by a respective DC motor (40, 42) and 44. The axes of the drive rods 6 intersect the upper surface of the upper chassis 4 at the three corners of an equilateral triangle. A level switch 8, 10 and 12 is located along each of the three sides of the triangle. Each level switch 8, 10 and 12 contains two switching elements each comprising a light emitting and a light responsive diode which are respectively switched when the side of the corresponding triangle tilts in a vertical plane in one sense and in the opposite sense ie the diode switches on when covered by the bubble when total internal reflection occurs, and switches off when covered by the liquid. Control means (52 to 74 Figure 6) are provided to respond to the three level switches to drive all three motors simultaneously to effect rapid levelling of the upper chassis 4 into the horizontal. <IMAGE> |
