| 摘要 |
<p>A spirit level with electrical illumination enables measurements to be made in situations where external illumination is inadequate. The two bubbles are each provided with an internal light source which may consist of a small bulb or light emitting diode. Alternatively, the light source may consist of a single small bulb (12) or light emitting diode. In this case the light is passed to the two bubbles via optical fibres (14,15). The spirit level also contains batteries (10,11) of suitable size and shape and a push button switch (13) or other suitable built-in switching device. The light source or sources may be integrated directly into the spirit level by being sealed in. The light sources need only be illuminated under adverse light conditions.</p> |
