Watt on NEO about 3 seconds delay

Anything about Power (watts)

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Watt on NEO about 3 seconds delay

Post by kalleonthebike » Wed Nov 14, 2018 8:58 pm

I'm using the Tacx utility app to figure out whats wrong.
Video showing the issue. https://www.youtube.com/watch?v=eX-aj_9o2PM

The rpm reading is responsive and accurate when I start pedaling. When I stop pedaling (free wheeling) the trainer, naturally, cannot tell if i'm pedaling slowely or if I have come to a complete stop. That seems alright.
The problem is with the Watt reading. When I stop pedaling and free wheeling, the power input is clearly zero. The trainer doesn't get this until about 3 seconds later. Similarly, when I start pedaling there is a delay of power. This makes, for example, Zwift a terrible experience.

Tacx support tells me that the delay is about inertia.
My respons to TACX support: I appreciate that your trainer emulates the inertia of a bike in motion, but this has nothing to do with the measurement of power...

Whats your experience? Is this how it should be???

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Re: Watt on NEO about 3 seconds delay

Post by Sorvoll » Thu Nov 15, 2018 4:20 pm

I can´t see any thing unusual in your video. The power will not go down to zero immediately, there is always a bit of delay/"smoothing". Without some delay would your watt go up/down to much to be useful because you are not producing power around the whole pedal stroke, normaly only during your downstroke. Without a delay/smoothing would it show close to two times during one pedalstroke.

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Re: Watt on NEO about 3 seconds delay

Post by kalleonthebike » Mon Nov 19, 2018 1:09 pm

I agree that some moving average thing from the variable power readings is appropriate. The thing is that power doesn't go to zero until about 3 seconds. This makes, for example, drafting in Zwift very difficult.
I was running at about 90 rpm, that is, 1.5 round per second. This gives us 9 strokes during the 3 seconds.

Anyone else that find that 9 strokes delay is a long delay? Normal?
Do you find it difficult to draft in Zwift?


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Re: Watt on NEO about 3 seconds delay

Post by Arked » Thu Jan 10, 2019 3:15 pm

If you want to slow down in Zwift don't stop pedaling completely, just soft pedal. If you stop pedaling completely some trainers and power meters stop broadcasting power and it's up to Zwift/software/bike computer to interpret it as zero watts (it takes around 5 seconds!). At least that's how it's made by official Ant+ guidelines. Thank's to that short 1-3s power sensor signal drops are not recorded.

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Re: Watt on NEO about 3 seconds delay

Post by EHB » Mon Feb 18, 2019 9:20 pm

The thing actually measured by most powermeters is force. To get power you then have to get a distance (eg. cadence) and do some maths. Cadence varies throughout the pedal stroke, so needs averaging a bit. Add to that the Ant+ specifications only require updating every second and a degree of delay is inevitable. Don’t know bluetooth specs, but doubt it is much different.

My crank power meter takes about 2 seconds to update on my head unit.

If the mechanical power were converted to a different type of power you could probably read it quicker, but then you’d still need it to be wired to avoid the wireless delays.

I’d guess in the Neo they convert mechanical power into electrical power and speed things up, so potentially they could speed things up, particularly if they used private ANT.

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