| 摘要 |
<p>The small spirit level with only one bubble is easy to handle, economical to make, multiple purpose and able to define both the vertical and horizontal directions. It has a transparent prismatic housing with an equilateral triangular base surface. A rotation symmetric hollow chamber constituting the bubble is partially filled with fluid. Its axis of symmetry lies parallel to the housing axis passing through the centre point of the triangular base. It may coincide with the housing axis. The hollow chamber may be cylindrical and half filled with the fluid. It has a circular marking around its cylindrical surface half-way along its axis of symmetry. The cylinder bases have straight marker lines. On one end they are parallel to the housing sides. On the other, they bisect the base triangle corners.</p> |
