| 摘要 |
An indicator device utilizes a pair of magnets to provide a missing-element indication. The indicator may be installed within a filter assembly such that, when a filter element is present, it urges a piston disposed towards the top of the indicator and one of the magnets to slide axially inwards through the indicator's housing and attract the second magnet. The latter then causes a button disposed at the bottom of the indicator to move axially inwards, such that no missing-element indication is provided. When the filter element is removed or is missing, the piston moves axially outwardly, thereby either reducing the force of attraction, or increasing the repulsive force, between the two magnets and causing the button to pop out through the indicator's bottom end and provide visual indication of a missing-element condition. The indication may also be provided as a remote electrical signal, which may be transmitted wirelessly.
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