How long before your powermeter sleeps?

pbassred

I just installed a 4iiii. You wake it up by rotating the crank. The same as the others I guess. How long after you ride before it sleeps. If I stop at a coffee shop or to adjust something or fix a flat, would I need to wake it and re-calibrate?

courtmed

A quick search found this -

PRECISION automatically detects rotation. Activate PRECISION by rotating the crank a few times. For
your information, PRECISION will enter sleep mode two minutes after not detecting any rotation.

Whether it's worth re-calibrating it after a few minutes I don't know though. How are you finding it generally?

pbassred

Thank you I missed that.
It went on last night, so the flippant answer is "I found it under my foot" . Seriously, its my first PM so I have nothing to compare it to. Initially I had difficulty registering it as a cadence device and gave up, but then a number came up on my Garmin so I guess that registering it as power does both jobs. I only need it to give me an indication. I'm not comparing my self to others so as long as it is stable its fine for me.
The battery door looks a little too flimsy (again nothing to compare it to) and I would have preferred it to be recessed a little - maybe with a coin slot. Its on a cyclocross bike so it might get a thump or 2. I might over wrap it.

Exactly what does re-calibration it do? I mean, its calibrated. Is it for temperature change? Temperature can change weather I stop or not. (see what I did there?).

Alex_Simmons/RST

Calibration is an often misunderstood term when it comes to power meters.

Calibration is a means by which you can validate a power meter is correctly measuring applied torque or force at different loads. The result of such calibration defines the "slope" value for that meter or in other words, how many units the meter registers per Nm of torque applied or per N of force applied. Some power meters enable you to check such things and only two models (SRM & Quarq) enable you to adjust that slope value if needed.

What most people (and many power meter suppliers) mistakenly call calibration is really a check of the torque (or force) reading when no torque or force is being applied. This is zeroing the meter, checking it reads zero when there is no torque or force being applied. this is a necessary but insufficient condition to validate the calibration accuracy of the meter.

Zeroing the meter is akin to making sure your bathroom scales read zero when there is no weight on them. Checking calibration is akin to checking the zero as well as making sure that when you put 50kg on the scale, the scales read 50kg.

So what most call calibration is in fact a setting of torque zero or setting of the zero offset value. It matters but isn't the whole story.