How does an indoor trainer measure cadence without cadence sensor?

A light bike doesn't replace good fitness.

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alcatraz
Posts: 1036
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Hey WWs...

I recently started using an indoor trainer (tacx t2180) and I noticed it reports my cadence. Quite accurately it seems. I can change gears and even if my speed increases but cadence drops, the measurement remains accurate.

I was just wondering how an indoor trainer can measure cadence when my bike has no cadence sensor?

Thanks
/a

mentok
Posts: 524
Joined: Sun Jan 01, 2012 9:58 am

by mentok

It measures torque which spikes at 9 o'clock and 3 o'clock in your pedal stroke. It detects the peaks in torque, measures their period and converts to an RPM measurement.

by Weenie


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TonyM
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Joined: Thu Jan 22, 2015 4:11 pm

by TonyM

Like for the Stages powermeter etc....

mentok
Posts: 524
Joined: Sun Jan 01, 2012 9:58 am

by mentok

stages and other crank based powermeters that don't use a reed switch and magnet combo use an accelerometer

alcatraz
Posts: 1036
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Thanks for explaining it. Makes a lot of sense....

mattr
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Location: The Grim North.

by mattr

And if you are very jerky or very smooth at pedalling, it can't always distinguish the individual pedal strokes.
Needs to have a measurable and repeatable difference between on power and off power.

by Weenie


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Leviathan
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by Leviathan

Also its perhaps worth noting that at the cheaper end the cadence output is worthless when accelerating or decelerating (ie all the time), Pretty sure Kinetic "estimates" my cadence using a random number generator.

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