| 摘要 |
<p>Measuring instruments which have a pointer (6, 28 or 42) positioned in dependence on the value of a measured quantity such as pressure or temperature. A switching device such as a reed switch (8, 25 or 41) is attached to the tail of the pointer, and electrical connections are made to the reed switch, for example, by an earth connection and an insulated connection such as a pin (22) and/or a sleeve (21). One or more pairs of magnets (4 or 40) are contained in a cover (5) which is rotatable with respect to the instrument about the axis of rotation of the pointer. The cover (5) may include a central annular recess and a central circular boss, and a magnet holder (3) and a setting knob (2) may be secured in the recess. The cover may be rotated by means of the knob to select a temperature or pressure at which the reed switch will be actuated.</p> |
