| 摘要 |
Apparatus for detecting the RPM of any rotational material handling assembly such as those used in coal mining or textile manufacturing and including the electrical relay switches to shut down the assembly motors when an underspeed condition is sustained. A proximity switch detects the periodic presence of a metal target attached to the rotating member of the material handling assembly and generates digital pulses responsive to the belt speed. The pulses are supplied to a missing pulse detector which generates an output if the time it takes the rotating member to complete one revolution is longer than a preset adjustable reference time. The output, which indicates an underspeed condition, is used to de-energize a relay which is interlocked to the rotational material handling assembly drive motor thus shutting the motor down.
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