How this kind of sensor work?

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Xavier Pacheco Paulino

Joined Oct 21, 2015
728
I found this sensor in a treadmill [picture attached]. There is a pulley attached to the motor shaft which has a small magnet. The sensor sees the magnet every revolution, I guess.

What kind of sensor is this? How does it work? Seems like a hall effect magnetic sensor. But it has only two wires, which got me confused.
 

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MaxHeadRoom

Joined Jul 18, 2013
22,018
A reed switch does not have very high operation capability so only used on relatively slow applications, if high speed is needed use the prox variety.
Also switch bounce is more prevalent on the reed ver.
Max.
 

ebp

Joined Feb 8, 2018
2,332
I think it is unlikely to be a reed switch if the end of the tube is oriented toward the magnet.

I think it is probably just a pickup coil - wire wound on a ferromagnetic (probably just iron) core. Each time the magnet passes a pulse is generated - typically something rather like a single sine wave.

A variable reluctance sensor works in a similar way, except the coil is wound on a magnet and it will sense a passing ferromagnetic object. They are often used for things where multiple pulses per revolution are wanted and using multiple magnets isn't practical. They can detect things like the teeth of a large steel gear.
 

MaxHeadRoom

Joined Jul 18, 2013
22,018
You can also pick up these hall effect gear sensors for an Auto wrecker, they are also made by Honeywell and used for crank gear tooth timing/sensing.
Max.


 
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