PM5 cadence spikes in recorded workouts

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patiofurniture
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PM5 cadence spikes in recorded workouts

Post by patiofurniture » August 12th, 2018, 11:27 am

Pretty much every workout I do will have some erroneous cadence data. It typically shows up immediately after the end of an interval or right when I start rowing after a pause. As a result, my max cadence for my workouts is always wrong (sometimes above 200).

Does anyone else have this issue?

See screenshots I uploaded to imgur from a recent workout.

https://imgur.com/a/XJJBZwX

One is the data plotted in Strava, the other is the same data plotted in Concept2 Logbook. Notice the spikes in cadence.

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jackarabit
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Re: PM5 cadence spikes in recorded workouts

Post by jackarabit » August 12th, 2018, 12:31 pm

The 200spm spikes are isolated and infrequent. 3 occurrences in 30’. Is anyone deceived by their anomalous amplitude? Are you? Do you remember the strokes recorded as 50~55spm @ 12’ 30”? You should recall these strokes if they are accurate records of cadence at that time because they fall in the range of unusual yet credible stroke rates. If you don’t recall an effort to produce those strokes, your max cadence was 40spm. I see artifacts of an imperfect or corrupted electromagnetic recording process (or wireless transmission environment) which deceive no one.

There would be an issue if the spikes occurred with a frequency sufficient to significantly alter average spm over 30’ workout. The machine doesn't distinguish signal from noise. That task falls to us.
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Citroen
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Re: PM5 cadence spikes in recorded workouts

Post by Citroen » August 12th, 2018, 4:09 pm

Don't cross post. I've deleted your duplicate.

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NavigationHazard
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Re: PM5 cadence spikes in recorded workouts

Post by NavigationHazard » August 13th, 2018, 2:46 am

Are you using a wireless connection to your device? A USB connection instead might eliminate any RF interference....
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Re: PM5 cadence spikes in recorded workouts

Post by Citroen » August 14th, 2018, 1:05 am

What model of rower is the PM5 mounted on?

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Re: PM5 cadence spikes in recorded workouts

Post by patiofurniture » August 24th, 2018, 1:00 pm

jackarabit wrote:
August 12th, 2018, 12:31 pm
The 200spm spikes are isolated and infrequent. 3 occurrences in 30’. Is anyone deceived by their anomalous amplitude? Are you? Do you remember the strokes recorded as 50~55spm @ 12’ 30”? You should recall these strokes if they are accurate records of cadence at that time because they fall in the range of unusual yet credible stroke rates. If you don’t recall an effort to produce those strokes, your max cadence was 40spm. I see artifacts of an imperfect or corrupted electromagnetic recording process (or wireless transmission environment) which deceive no one.

There would be an issue if the spikes occurred with a frequency sufficient to significantly alter average spm over 30’ workout. The machine doesn't distinguish signal from noise. That task falls to us.
This is silly, I know it's obvious which points are fake, but I don't want to have to clean the data. Is it wrong to expect accuracy from a $1000 product? Even just one extreme point will throw off the scale for the graphs, and then the rest of the row will look like it was all at a constant cadence - so you lose the ability to perform a quick visual analysis.

Anyways, my question wasn't "Should this behavior bother me?" my question was "Does anyone else have this issue?" and "can anything be done about it?" (aside from feeding all my workout files through a cleanup script which is what I do now).
NavigationHazard wrote:
August 13th, 2018, 2:46 am
Are you using a wireless connection to your device? A USB connection instead might eliminate any RF interference....
Yes thanks. I'm using the ErgData app connected via BLE. I will try the cord and see if I still get the issue. But that would just identify the source of problem - it's not a fix (for me at least) bc then I need to carry the phone mount and cable with me, and I would probably prefer to just use a clean up script instead of carrying those items around.
Citroen wrote:
August 14th, 2018, 1:05 am
What model of rower is the PM5 mounted on?
It's a Model D.

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c2jonw
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Re: PM5 cadence spikes in recorded workouts

Post by c2jonw » August 24th, 2018, 2:54 pm

Pausing during a workout, especially if the pause is more than 5 seconds, will almost always result in an abnormally high or low stroke rate value. When you say it occurs "immediately after the end of an interval" what type of interval workout are you doing? Does the anomaly ever occur when you are just doing a steady state, non-stop workout? C2JonW
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Re: PM5 cadence spikes in recorded workouts

Post by jamesg » August 26th, 2018, 1:51 am

I get these spikes, in the PM bar chart, very frequent if a laptop is connected and more so if powered. Removing these connections and power supplies reduces the spikes substantially. They have no effect on averages or on training so have no importance.

A loss of impulse train due to beat frequencies (with 50 or 60 Hz power) will necessarily appear as the end of a stroke. The PM shows a double stroke in place of one, the second at high rating or as 1xx (seen as xx, due to truncation right and left).

Odd things can be seen in the force curve too, with scattered data points which often coincide with spikes.

External connections seem to take for granted the PM calculations, apparently doing no sums of their own; so all blips show.
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Re: PM5 cadence spikes in recorded workouts

Post by patiofurniture » August 28th, 2018, 7:12 pm

c2jonw wrote:
August 24th, 2018, 2:54 pm
Pausing during a workout, especially if the pause is more than 5 seconds, will almost always result in an abnormally high or low stroke rate value. When you say it occurs "immediately after the end of an interval" what type of interval workout are you doing? Does the anomaly ever occur when you are just doing a steady state, non-stop workout? C2JonW
Ya it happens after a pause, I haven't seen it during a non-stop workout yet.

Say I do a 4 min interval at a given pace, then I rest for a minute before starting another 4 min interval. These are not programmed rest periods, just resting while using the "free row" setting. It's hard to tell if the spike happens right at the end of the interval, or right at the start of the next interval, bc the monitor stops recording when you stop rowing.
jamesg wrote:
August 26th, 2018, 1:51 am
They have no effect on averages or on training so have no importance.
I realize that not everyone takes issue with these spikes, but *I* find them annoying because I am interested in what my max cadence was for a given workout. I am also interested in seeing how my cadence varies over the course of a workout, and as I said before, these spikes will effect the y-axis scale of the graphs. For example, when you have spikes that are above 200 spm, then on the graph its very hard to tell the difference between 35 and 40 spm, bc everything is scrunched down so that the data pt in the 200's is visible.

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Re: PM5 cadence spikes in recorded workouts

Post by jamesg » August 29th, 2018, 1:35 am

Try adjusting the y-axis, setting a top limit manually.

The PM too can show you how ratings vary, and power too, by setting shorter splits.

Intervals in Just Row will always give dodgy numbers, since the PM does not get enough information when we stop or start.
77y, 188cm, 85kg, MHR 160. Last 2k (May 1018) 8.37@23

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jackarabit
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Re: PM5 cadence spikes in recorded workouts

Post by jackarabit » August 29th, 2018, 9:01 am

. . . and as I said before, these spikes will effect the y-axis scale of the graphs. For example, when you have spikes that are above 200 spm, then on the graph its very hard to tell the difference between 35 and 40 spm, bc everything is scrunched down so that the data pt in the 200's is visible.
Looks to me that Concept 2 is taking a bit of a hit here. ErgData, a C2 product distributed as a free app, limits vertical scale, in the example shown, to 0-100 spm, thereby truncating the 200 spm spikes and preserving reasonable resolution in the rate range you are interested in. The Strava aspect ratio is squashed flat by the choice of 0-232 rpm/spm range for the vertical axis. The fact is that you did not pay 1K$ for ED; the big ticket item is the rower. At 59$ per annum subscribed, I assert that Strava is the poor bargain on the evidence of the graphs shown.
There are two types of people in this world: Those who can extrapolate from incomplete data

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patiofurniture
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Re: PM5 cadence spikes in recorded workouts

Post by patiofurniture » August 29th, 2018, 11:59 am

jackarabit wrote:
August 29th, 2018, 9:01 am
Looks to me that Concept 2 is taking a bit of a hit here. ErgData, a C2 product distributed as a free app, limits vertical scale, in the example shown, to 0-100 spm, thereby truncating the 200 spm spikes and preserving reasonable resolution in the rate range you are interested in. The Strava aspect ratio is squashed flat by the choice of 0-232 rpm/spm range for the vertical axis. The fact is that you did not pay 1K$ for ED; the big ticket item is the rower. At 59$ per annum subscribed, I assert that Strava is the poor bargain on the evidence of the graphs shown.

Yeah that's true, Strava is a poor bargain imo, and the concept2 graphs are better in this case with the max SPM of 100. But I don't agree with the ED claim, because ED (which they market) factored into my buying decision for the rower. Do you think this is an ED specific issue, and do you have any recommended free alternatives that I should check out?

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