Cadence Sensor 2 issue

This cadence sensor is based on an acceleration sensor. On a relatively steady road it will trigger once per crank revolution, but on a (very) bumpy, hard road it can also get triggered by a bump, leading to such peaks. It can also be that at a certain point you peddle backwards e.g. for a quarter of a revolution and then quickly again forwards, producing 2 successive triggers in a short time - again a peak.

That latter scenario also happens with the GSC10 (combined speed/cadence sensor), that is based on a reed-relay and magnet, triggering every time the magnet passes by the sensor; you'll find with such kind of sensors exactly the same peaks.

Somewhere I've read that this cadence sensor works using magnetic fields, sensing the relative rotation of the ambient magnetic field rather than using accelerometers.  IDK, but this may be because current draw is less for magnetic sensing than using accelerometers.  I have not had any spiking from these sensors.

With the GSC10 which uses a crank magnet, if you coast with that crank arm back near the GSC10 pickup, bouncing can cause a very high cadence reading.

Thanks a lot... today it did it again. Actually it does at any ride

looigi, the Garmin speed sensor 2 contains indeed a magnetometer measuring the 3D components of the ambient magnetic field, and can like that see when it makes a full rotation - see https://support.garmin.com/en-US/?faq=9NL91YJSJd3Tnyif9jRSy6.

But I'm still convinced that the cadence sensor 2 is an "ordinary" accelerometer. Not only because DC Rainmaker says so (https://www.dcrainmaker.com/2014/05/garmins-spd-cad-magnetless-sensors.html), but taking also some "experimental evidence" into account. As I had noticed myself similar spikes with that cadence sensor, I did some tests and have seen that the cadence displayed on my 830 occasionally jumped to values well above 0 exactly after hitting a bump on a downhill paved road while I definitely didn't move my pedals at all for several hundreds of meters. That surely points in the direction of an accelerometer ...

Thanks!

The wheel sensor does use the ambient magnetic field per below.   I'm pretty sure I read the same about the cadence sensor but I can't find the reference, so IDK for certain.  I remember having assumed it was accelerometer based and being skeptical about  it using the ambient mag filed.  Many pedal and crank PMs use accelerometers for cadence and crank angle, including the Garmin Vector pedals.

support.garmin.com/.../

The cadence sensor uses accelerometers 

If you’re using the GCS10, I had this problem with my original 800.  Garmin suggested a few things that didn’t work and sent me a replacement sensor.  That solved the problem.

 If it’s the newer separate pedal mounted cadence and hub mounted speed sensor I haven’t had this problem with those. 

Unfortunately is the latest model and not the GCS10... I will contact them just in case! Thanks a lot