Pointer movement with upper and lower limit switches - has spring-loaded adjustable switching arm contacting stud on pointer to signal threshold value

摘要

The indicator movement is fitted with a switch contacts to provide signal outputs at a lower and upper limit. The limits can be set on the dial of the instrument. The limit adjusters each have a fixed arm (8, 6) the first having a stop (9) acting as a fixed switch contact. Two moving arms(10, 11) have contact studs (13, 16) and permanent magnets (12, 18, 22) and are held under the tension of a spiral spring (15, 19). When the pointer moves beyond the lower limit position a pin attached to it moves both moving arms with it. Their contacts remain closed. A second contact between the second moving arm and the first fixed arm is opened. When the upper limit is reached, the coupling between first and second moving arms is broken and the latter returns under spring tension to the first fixed arm, remaking the contact. The contact between the moving arms is broken.