Latency of the direto in ERG mode with Zwift

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raphnou
Posts: 44
Joined: Wed Apr 11, 2018 9:23 am

Latency of the direto in ERG mode with Zwift

Postby raphnou » Thu May 31, 2018 2:44 pm

Hello Elite,

Here is the graph of an easy 30x30 sceance in Zwift (155W / 210W) @ 100rpm

each point corresponds to one second

We can determine the Direto latency time of about 7/8 seconds at the ramp up, there is also a latency at power release.

With a precise power sensor, the latency is a decisive point to compare the trainers between them.

Why manufacturers do not communicate this information that can be decisive for structured training and predefined by the application used.
Attachments
cheetah total.jpg
cheetah total.jpg (89.03 KiB) Viewed 195 times
cheetah direto latence up.jpg
cheetah direto latence up.jpg (88.43 KiB) Viewed 198 times

raphnou
Posts: 44
Joined: Wed Apr 11, 2018 9:23 am

Re: Latency of the direto in ERG mode with Zwift

Postby raphnou » Fri Jun 01, 2018 3:58 pm

Hi,

I repeat my graph above, to add a precision.

I took the selection # 1 which corresponds to the points in the Direto precision range which is +/- 2.5% or according to the requested power 210w. The range of points is between 204.75w - 215.25w

First observation, the average power of the selection # 1 is 210W on this range, for a requested power of 210W, it is really beautiful precision. :shock:

Unfortunately for this interval of 30 seconds, the points of the selection # 1 is only 25 seconds instead of 30 seconds.
No problem just add 5 seconds to the interval. :ugeek:

But if I decide to enlarge the selection to extend it to 30 seconds on the best points of the requested power in this range of the selection # 2
So the average is 206w, and more exactly 206.64w on 30 seconds for 210W asked, it's still in the precision range announced and it's excellent. :mrgreen:

I looked at other intervals and it's still very good.

Finally on this test of 30x30 to 110w/210w, the latency is not problematic, it just results in erroneous graphics in garmin connect for example, which must be corrected on the timing.

It will be necessary to check on higher powers if the latency does not increase :geek:
Attachments
cheetah selection 1.jpg
cheetah selection 1.jpg (98.89 KiB) Viewed 182 times
cheetah selection 2.jpg
cheetah selection 2.jpg (108.44 KiB) Viewed 182 times

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Elite Admin S
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Re: Latency of the direto in ERG mode with Zwift

Postby Elite Admin S » Mon Jun 04, 2018 8:46 am

Hi

Direto adjusts resistance using a stepping motor.
When requested power/slope changes, the motor moves a magnetic arm to match the requested value.
Of course this movement requires some seconds. Also, the software will add other seconds of delay (it has to verify the data, see the variation, send a command to the motor). At the end, the entire process can last some seconds (depending also on how big is the resistance variation - and consequently, the movement to do). A 5-10 seconds of delay is quite common.

raphnou
Posts: 44
Joined: Wed Apr 11, 2018 9:23 am

Re: Latency of the direto in ERG mode with Zwift

Postby raphnou » Mon Jun 04, 2018 4:37 pm

Elite Admin S wrote:Hi

Direto adjusts resistance using a stepping motor.
When requested power/slope changes, the motor moves a magnetic arm to match the requested value.
Of course this movement requires some seconds. Also, the software will add other seconds of delay (it has to verify the data, see the variation, send a command to the motor). At the end, the entire process can last some seconds (depending also on how big is the resistance variation - and consequently, the movement to do). A 5-10 seconds of delay is quite common.



This is common to all Direto or Drivo is it more responsive?
I thought I read that the Drivo had 4 seconds of latency ...

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Elite Admin S
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Re: Latency of the direto in ERG mode with Zwift

Postby Elite Admin S » Tue Jun 05, 2018 8:47 am

It's not possible to tell how much is the latency, as it depends on how much is the resistance variations (the bigger the variation, the longer the the delay).
The motor in the Drivo is a little slower - BUT the power range is higher, so it is necessary less movement to make the same power variation.
In the end, they are quite similar.


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