| 摘要 |
Apparatus for detecting excessive slippage of a conveyor belt, as used, for example, in the coal mining industry includes electronic switching devices. A ring having a plurality of magnets thereon is mounted on a belt roller, and a detecting coil produces voltage pulses in response to the passage of the magnets. The voltage pulses are amplified, squared, and replaced by fixed width pulses at a frequency proportional to belt speed. The fixed width pulses are integrated to provide an average voltage having a value proportional to the conveyor belt speed. The average voltage is compared with an adjustable reference, and is used to turn off the belt driving motor when belt speed drops below a predetermined threshold.
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