Originally Posted by
bungis
This might not be the case with power2max track as it doesn't auto-zero. It's manually zeroed by the user at the beginning of the ride or after changing rings. Couple other notes about this PM:
It's actually Rotor's road crankset with the following adjustments for track use:
- 144 BCD
- No auto-zero as mentioned
- Chainline
It uses a road BB and not Rotor's track BB, not sure if that's a big deal tho.
edit: I'm going to ask power2max about this specifically and report back here.
edit2: power2max said it was the low and high-frequency changing of RPM of a standing start that is the limitation. Hopefully they respond with specifics with the lower-bound RPM or typical time-frame before it transmits accurate readings.
edit3: 20 RPM and two crank rotations before it transmits data
Well, it's not an issue of auto-zeroing. I think it's more the fact that cadence and power are transmitted via the same transmission from the crankset. Actually it's more like cadence is calculated based on how often power is being transmitted via the single reed switch which also pulls double-duty as a cadence counter.
In order to calculate cadence, you need at least 2 readings. The cadence is calculated as 1/(time between the two readings).
Being that that power meter probably only has 1 reed switch, it will take about 2 pedal strokes to get enough of a sample to create a cadence.
The cadence value is used along with torque to calculate the power.
You can't have power till you have cadence. You can't have cadence till you get 2 transmissions from your reed switch. You can't have 2 transmissions from your reed switch till your pedal comes around between 1 and 2 complete rotations.