Hall-Effect sensor failure at narrow RPM?

Question

How is it that Hall sensors and/or wiring can fail (by various reports) within a relatively narrow RPM band, yet switch well (or at least well enough) at other parts of the RPM band?

Presumably the scope waveform would be abnormal at the problem RPM zone

- either a drop in current supply, noisey ground, or roundness or incorrect voltage in the on/off switching

Would the waveform possibly look "square" (relative to its duty cycle) at RPMs where the sensor apparently performs well (or well enough to slip inside the operating range specs for whatever application it's being used on)

Thank you, Lance

Bill Sloman · Accepted Answer

What form does this failure take? What sort of motors are driving the shaft being monitored?

One possible explantion for this sort of failure would be a mechanical resonance along the shaft or in the Hall-sensor mounting. This could be excited at around the offending range of RPMs, and could then produce interesting displacements between the Hall sensor and the magnet it is detecting.

------- Bill Sloman, Nijmegen

LanceM · Answer

Automotive application. I've just been interested in reports of either failing distributor or crank mounted H-E sensors, and possibly even more so associated wiring, where car surges/hesitates/bucks between (for example) 2500 RPM - 3000 RPM, under either load/acceleration or at steady-state (light-to-moderate load), yet performance appears fine above and below the problem RPM zone. Securing/cleaning/replacing the wiring connecting harness, or the sensor, fixes the driveability problem. Thank you

Hall-Effect sensor failure at narrow RPM?

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