Power instability with ERG mode + external power meter

General Discussion
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1

Hello, I use Zwift with Tacx Genius Smart T2080 trainer - when I use only trainer data (it’s provide power, speed, cadence and control) everything is ok and stable. I also have external power meter - powerbeat on my crank left arm and Bryton monitor + phone with ANT+ to monitor power from this meter.

I also have ANT+ USB dongle for Mac, so can use Powerbeat as power source in Zwift. It works fine, but power is very “ustable” during tranings and enabled ERG mode - it fluctuates a lot (in small values, but fluctuates), so I often see “more power” info and it’s problematic. I think it’s because Zwift must get data from powerbeat, calculate, and then send to Tacx to change resistance - maybe it takes to long time to work properly?

I prefer to use external power meter with Zwift, because it’s more accurate than trainer. What can I do to fix this?

2

Fluctuating when using a power meter combined with a smart trainer is normal. At the end of a training segment the average power should match the target average power. That said you’ll get better results with a direct drive trainer as they have more accurate power. The closer power accuracy is between the trainer and your power meter the less fluctuation you will have (or that’s my experience).

3

I make one change - use ANT+ for all instead of Bluetooth.
Before that, I used ANT+ to see power/cadence from Powerbeat meter + HR, and Bluetooth to control Tacx. Now also use ANT+ to control trainer and… it still fluctuates, but much less, power chart is flatter than before.

Think that was caused by lags (bluetooth?).