PM5 - Wattage smoothened

Discuss all things related to the BikeErg, Concept2's newest product.
Post Reply
Livio Livius
1k Poster
Posts: 136
Joined: December 5th, 2009, 5:20 pm

PM5 - Wattage smoothened

Post by Livio Livius » June 7th, 2019, 2:56 pm

Does anybody know how much seconds the wattage show on the PM5 are smoothened, is it 1 sec, 5 or maybe 30 sec?

User avatar
johnlvs2run
Half Marathon Poster
Posts: 3676
Joined: March 16th, 2006, 1:13 pm
Location: California Central Coast
Contact:

Re: PM5 - Wattage smoothened

Post by johnlvs2run » June 7th, 2019, 3:48 pm

I tried watts for starts this morning, and they were jumping all over the place.
They appeared to be delayed, and then would jump way up.
After I finished a start and took a few easy strokes, the watts jumped up 30 points higher.
They are neither accurate nor reliable, so I won't use them again.
73 5'8 155
age 70+ world record pace per weight percentages
skierg: 100m 87.4 / 500m 86.2 / 1k 85.9 / 2k 89.4 / 5k 87.6 / 10k 89.4 / 60' 92.0 / 21k 93.6
my training log

jamesg
Half Marathon Poster
Posts: 2488
Joined: March 18th, 2006, 3:44 am
Location: Trentino Italy

Re: PM5 - Wattage smoothened

Post by jamesg » June 10th, 2019, 10:43 am

The erg measures the work done in each single stroke, using flywheel data and time. The PM divides this Work by the time taken for the stroke (finish to finish) and displays the result as power in Watts.

The Watt reading and its derivatives (pace, kCal etc) update immediatly after the finish.
78y, 188cm, 87kg, last seen MHR 163. 2k (24 May 19) 8.46.6@22

Allan Olesen
2k Poster
Posts: 374
Joined: April 27th, 2018, 6:40 am

Re: PM5 - Wattage smoothened

Post by Allan Olesen » June 10th, 2019, 11:37 am

jamesg wrote:
June 10th, 2019, 10:43 am
The erg measures the work done in each single stroke, using flywheel data and time. The PM divides this Work by the time taken for the stroke (finish to finish) and displays the result as power in Watts.

The Watt reading and its derivatives (pace, kCal etc) update immediatly after the finish.
To me, it seems to be an average of the power for the two last strokes.

If you suddenly change your stroke force, but maintain stroke rate, it will take two strokes before the power on the screen has fully catched up.

User avatar
Citroen
SpamTeam
Posts: 5882
Joined: March 16th, 2006, 3:28 pm
Location: Basingstoke, UK

Re: PM5 - Wattage smoothened

Post by Citroen » June 10th, 2019, 12:13 pm

Does the bikeerg work the same way? The movement on a bike isn't a series of discrete strokes it's a continuous motion.

jamesg
Half Marathon Poster
Posts: 2488
Joined: March 18th, 2006, 3:44 am
Location: Trentino Italy

Re: PM5 - Wattage smoothened

Post by jamesg » June 10th, 2019, 1:14 pm

With continuous action, presumably the bike-erg once calibrated, calculates delivered power directly from flywheel speed. If so it could average the observed speed with a certain frequency (maybe over one crank turn) and use that average. Watching the screen when starting should soon give an idea of the display refresh rate.

Fan speed and power are related by a cube law (W=kV^3), and calibration serves to find k.

On the rower too, the flywheel has to react to what we do, before PM can show any stable change. This can take some time, certainly more than a single stroke. Using Watts this is clearly seen given the high resolution (usually better than 1%).
78y, 188cm, 87kg, last seen MHR 163. 2k (24 May 19) 8.46.6@22

Allan Olesen
2k Poster
Posts: 374
Joined: April 27th, 2018, 6:40 am

Re: PM5 - Wattage smoothened

Post by Allan Olesen » June 10th, 2019, 3:13 pm

Citroen wrote:
June 10th, 2019, 12:13 pm
Does the bikeerg work the same way?
Sorry. I hadn't noticed that the question was asked in the BikeErg forum.

Post Reply