Power meter record disparity

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Piotr Andrzejczyk

• October 02, 2021 17:05

Hello,

Since I ride my MTB with Karoo I have noted disparity with power reading/records.
Using various software there was the same problem with power readings.

The problem occurs when you stop pedalling, power meters stop sending data to a device for second or two.
Then: Karoo2 repeats last received power number and records it into .fit
Other devices: (I tested Zwift, Garmin Edge 510, Fenix 5, Wahoo app) in this case reads no data as "0 value" with is correct

By that Karoo2 data sets looks sluggish, like the connection powermeter <-> Karoo is crappy. But not only look is an issue. Power records are big problem because using Karoo you will have different power records - most likely higher because Karoo records last number even when you not pedalling anymore - you will get probably 2 extra second of "free" power.

Critical power chart of recorded data on Karoo2, Garmin Fenix 5, Garmin Edge 510
I was pedalling 5sec ON, 5sec OFF, 10sec ON, 10 sec OFF just to see this laggs
Also weblink to comparison https://zwiftpower.com/analysis.php?set_id=170615

Below screenshot of raw data of power record - Karoo2 fit file from Dashboard

At that point, I consider stopping using Karoo for MTB/XC races because power records have different standards than all other devices on the market. It is not compatible and not correct. Hammerhead Team please look up this case asap.

PS tested on powermeters using ant+ protocol: Assioma Duo, Xcadey Xpower-S, Direto XR, Powertap G3 hub

3

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  Piotr Andrzejczyk

  • October 03, 2021 18:20

  Another set of data 3.87% (10 wats) Normalized power difference on 2 hour ride

  

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  Johnathan Freter

  • October 03, 2021 20:54

  It really annoys me that on a garmin you can choose between 1s and "smart" recording but with the K2 it's just whatever they set it at. I'm not even asking for SRM PC* level of recording.

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  Joen Tolgraven

  • October 08, 2021 17:19

  So you're saying that what's being displayed on the device (0 as soon as stop pedaling) and what's being written to .fit is not the same? That seems like a pretty major issue.

  It is however definitely not universal. Looking at my last ride power falls to zero without any repeating values - indeed cadence actually lags behind by a tick or so. I assume this means my PM actually sends a zero value and doesn't just stop transmitting.

  But they should obviously cover all bases here and properly handle devices that work differently. Even if it means micro-dropouts will be less graceously handled.

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