Less laggy power meters

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warx
Posts: 20
Joined: Sat Jan 03, 2015 1:45 am

by warx

So looking at getting what will be my third power meter and although I love my power2max (p2m) Type S the lag is sometimes frustrating. I measure it at 3.5-4 seconds reporting to my Garmin 520. In comparison my old Powertap G3 hub reports in 0.5 secs. When doing NM or VO2 intervals it is hard to gauge the power (e.g. aiming for 170 or 200% FTP interval ends up as over-under hysteresis) . On short (~15km) climby time trials I usually resort to the Powertap. Otherwise I love my P2M it's waterproof, knock-proof, never has data/sync glitches and the data is good. It's been dragged (and dropped) in rocky creeks and subjected to single-speed 'cross races.

I saw there is a new P2M (NG waiting in the wings) but I am wondering about trying the Quarq Speczd Speedzone for FACT Pro crank (not sure which Quarq it is equivalent to). Anyone have a comment on how much lag Quarq meters have? Will they withstand the same abuse?

Perhaps I need to calibrate myself and not be so intent on the real-time data and go more on feel for these short intervals. :-|

berend
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Joined: Thu Apr 21, 2016 7:51 am

by berend

I've had an Ergomo (Ergomo head unit), and currently I have a Quarq Cinqo (Garmin head unit).

The Ergomo was much less laggy (from memory), and it was an all-round better head unit. I think the problem is Ant+, and Garmin, not the power meter. I'd like to hear from a Quarq+Joule or SRM head unit.

For me, it's most annoying when hitting "lap" (oh, how I'd love an interval mode on the Garmin).

Ant+ only reports every second (Quarq has a faster report mode, you can set it using Qalvin), and I think the Garmin 500 screen is terribly slow in screen refreshes, and I think the Garmin is also terrible in averaging power.

I'll tell you why I think the Garmin is the culprit:
1. display lap-instant, and lap-average power
2. pedal steady (say 200 watts, whatever...)
3a. start a lap (interval)
3b. stomp it
4. lap-average power starts below 200 and slowly builds up

Remember that the power meter itself has no history, it can only provide instant power. History (and hence lap average) comes from the head unit.


I can't tell you if it's better or worse than a P2M, but it's sure worse than the Ergomo.

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Nejmann
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Joined: Mon May 06, 2013 6:25 pm

by Nejmann

Quarq etap and garmin 1000 here. No problems at all.

Stueys
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Joined: Sat Nov 22, 2014 1:12 pm

by Stueys

Power2max type s and vector here, both on a garmin 1000 head unit. I don't see any lag difference between the 2 power meters, and I would say both are pretty instant..

Stalkan
Posts: 109
Joined: Tue Sep 21, 2010 1:04 pm

by Stalkan

I have a P2M Classic, 4iiii, and SRM. All three take a second to report to the my 520 but once I have numbers I merely hold what I have or adjust up a bit or down to get me in the zone. Not sure how a 3 second lag would ruin your WO other than pushing too hard to get up then letting way off to get back down. Try being smoother, that is less forceful with your change in effort, and see if you can't get your lag to not matter. FWIW, I look at instant, 3s, 10s, 30s and lap power to see which way I am trending and this helps me be pretty darn smooth when doing any interval work.
Last edited by Stalkan on Mon Aug 29, 2016 1:56 pm, edited 1 time in total.

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ms6073
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by ms6073

warx wrote:I measure it at 3.5-4 seconds reporting to my Garmin 520

I assume this is for outdoor training? Did you configure your Garmin to use a 1-second recording interval instead of Smart Recording (4-5 seconds)? My Garmin Edge 520 updates every second and given the stochastic nature of power output from crank based powermeters such as P2M and SRM, I suggest you consider adding an interval data page to the Garmin that has only the interval specific data fields such as lap time, speed, %FTP, 3-Second Avg Power, 30-Second Average Power, Cadence, and HR %Max.

berend wrote:Ant+ only reports every second (Quarq has a faster report mode, you can set it using Qalvin), and I think the Garmin 500 screen is terribly slow in screen refreshes, and I think the Garmin is also terrible in averaging power.

I think that would depend on the type of powermeter in use as well as the age of the firmware/ANT+ Power profile and would be dependent on how the head unit is configured to display information:

All of the broadcast power messages have an Update Event Counter that is used by the receiver to calculate information accurately. There are two methods used by bicycle power sensors for information updates:

Event-Synchronous Update e.g. the power information is updated each time the power sensor detects a new crank rotation.
Time-Synchronous Update e.g. the power information is updated at 1Hz.
- Michael
"People should stop expecting normal from me... seriously, we all know it's never going to happen"

warx
Posts: 20
Joined: Sat Jan 03, 2015 1:45 am

by warx

Wow! - thanks for the replies! So a bit on my testing;
I set up a screen with several power options - as you say FTP and the various averaging options (least, 3s and 10s) and timer (running).

Cruise on flat without pedalling until everything is "0". Start pedaling at ~90rpm@250W on a round time (like 01:00). For the Powertap ALL the numbers change before 1 second is reached on the timer and the update looks like twice a second to me. For the P2M no number changes until the timer says 4 seconds (or sometimes just before). Likewise when stopping pedalling - the 1s average number drops to "0" in about 1-2secs for Powertap. the P2M reports full power for the next 4 seconds then drops.

So the scenario for high intensity intervals: (e.g. say 8 sets of 20x10 target @ 180% FTP). I don't know I am up to 180%FTP until the 4th or 5th second of a 20 second interval so it's pretty hard to tell. Up at those ranges you could likely be at 30% off, do some quick head math, adjust, check again in 4 seconds, adjust - urgh interval over.

Even when trying to stick at 105% for say a 25min TT it does make a difference. I know power meters are capable since my Powertap does it flawlessly with both my Garmin 500 and 520. I asked P2M Canada and they said the lag most probably can not be reduced. I was hoping for some firmware update magic.

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Sacke
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Location: South of France

by Sacke

Definitely a Garmin problem.

I recently bought a Rotor inPower, and in order to get the signal to my Polar V800, I also bought a Viiiivo HR strap that receives the ANT+ signal from the power meter and sends it through Bluetooth Smart to the Polar V800 watch.

I rode a couple of rides with both a Garmin 510 and the Polar, and to my surprise, the delay of the displayed wattages was LONGER on the Garmin, than on the Polar, that receives the information via the Viiiiva HR strap.

The only thing I need the Garmin for, is calibration, because as it seems, getting the Rotor software to work on Mac OS X El Capitan requires developer skills beyond following tutorials, but that is another story.

warx
Posts: 20
Joined: Sat Jan 03, 2015 1:45 am

by warx

Interesting as the NG P2M is supposed to transmit BLE as well as ANT+ but obviously the 520 won't use that. Maybe the new Garmin 820 adds BLE sensors. I will try with my Viiiiva and Samsung S5 IPbike to check this out before I give up on P2M. However, I could see this adding 0.5-1sec difference but not 4secs

Would be interesting to have software that does ANT+ & BLE sniffing. Hmm, I guess I could time my TrainerRoad and Suunto stick also.

On an unrelated note I had issues with my Viiiiva and 520 (spikes of 240bpm). 4iiii fixed that eventually but I had already switched to a Garmin HR.

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ms6073
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by ms6073

warx wrote:For the P2M no number changes until the timer says 4 seconds (or sometimes just before). Likewise when stopping pedaling - the 1s average number drops to "0" in about 1-2secs for Powertap. the P2M reports full power for the next 4 seconds then drops.

Since your Garmin is correctly displaying power metrics for the other PM, the ANT+ profile for the PM's is a standard that is not really open to interpretation, so would this not point to an issue with the P2M instead of the Garmin?
- Michael
"People should stop expecting normal from me... seriously, we all know it's never going to happen"

RyanH
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by RyanH

Related to this, has anyone noticed their headunits displaying power for a few seconds after you stop pedaling? The SRM seems to do this for 3-5 seconds.

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boysa
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by boysa

I currently run a P2M with a Garmin 520. I experience the same issue as op, but afaik this has been out in the public domain for a long time. P2M just lags, and there isn't much you can do about it.

When I do an interval, for example, I stomp on the pedals as soon as the timer goes, usually even just before, but when I look at the file in GC there is clearly a lag of around 3-8". So, if I want to be precise, I merely pare down the interval. For a 1' rep, it's usually about 52-55". Oh well.

I previously ran a Quarq Elsa and this problem didn't exist. In fact, one of the first things I noticed when switching was how my 5" and peak power dropped with P2M. Enough time has passed, however, where I'm comparing "apples to apples."

As for the back end, GC has a filter built just for this purpose. It removes the data added at the end.
"Deserve's got nothing to do with it." William Munny

warx
Posts: 20
Joined: Sat Jan 03, 2015 1:45 am

by warx

Google Drive managed to compress the video below enough to make the TrainerRoad display practically unreadable but you can still see when it is not 0. Looking at the time its like TrainerRoad displays non-zero at 4 seconds and Garmin 520 at 5 seconds. Likewise at the stop end too.

I re-did my Powertap G3 test (indoors, with Garmin HR strap). It's actually 3 seconds lag to Garmin and 2 to TR. This was more than my last test. I went outside and re-ran them. Powertap -> 520 2 seconds lag - BUT if wearing the HR 3 seconds lag. Must be an ANT thing. Bring on all BLE sensors!

Anyways the perceived difference between 3 and 5 seconds is a lot. I think I might try the Speczd branded Quarq (can buy it with the bike) as now I totally curious :-) Or wait to see how the P2M NG performs in BLE mode (will need new head unit of course).

Here's the video below is the P2M S starting on 00:00 and stopping on 00:10:

https://drive.google.com/file/d/0B1XDut ... sp=sharing

GothicCastle
Posts: 304
Joined: Mon Jul 04, 2016 1:52 am

by GothicCastle

berend wrote:For me, it's most annoying when hitting "lap" (oh, how I'd love an interval mode on the Garmin).


The Garmin will do that if you program in your workout and run in workout mode, if I understand what you are saying. It creates a lap for each segment of your workout.

zirxo
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Joined: Wed Mar 19, 2014 12:46 pm

by zirxo

The workout feature on the Garmin units is perfect for shorter intervals like 15/15 or 30/30 or if you're doing some crazy complicated session with lots of intervals of different length. It's so nice to not have to remember to press a button or check the time when you're on your 48th 15/15. ^^

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