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PostPosted: Wed Jul 04, 2012 2:41 am 
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Joined: Sat Dec 13, 2003 2:25 am
Posts: 4453
Location: Canada
fankozola101 wrote:
Geoff, are you saying...

If: You manually enter a new slope constant in the Power Control (head unit)

Then: the Power Control (head unit) sends a signal to the Power Meter, which changes the slope constant stored on the Power Meter.

And: This new slope constant stored on the power meter is what a Power Control (head unit) will detect (in future) when in "auto detection" mode.

Sorry for missing this (Canada Day, etc.) I also think that this answer may cover-off some of the other stuff you have asked. The answer is a qualified 'no'.

The 'auto-detect' feature is unique to the wireless SRM PowerMeter (i.e., not found on wired PowerMeters), so by default, only the PC6 and PC7 PowerControllers can 'benefit' from it. When you change the slope in manual mode using the SRM software, the slope stored in the PowerController is not then changed so that the 'auto-detect' feature will, thereafter, apply the new slope. Rather, the PowerMeter will default to the original, factory slope setting.

I know. It's lame. I imagine that this will lead to another round of comments about SRM seeking to further secure 'repeat' business. There is a way to do it, though...


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PostPosted: Sun Jul 07, 2013 5:11 pm 
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Joined: Mon Sep 21, 2009 11:12 pm
Posts: 31
Tapeworm wrote:
I pinched this from a forum somewhere, been sitting in my docs files for ages. Easy as it gets.

How to recalibrate SRM?

1. Look for a weight of about 30 to 40 kg. Hang it on a cable of about 25 cm, so that the weight does not touch the floor when it is hanging on the horizo ntal crank pedal, or take a longer cable and put the bike on a table.

2. Calculate the weight in Newton. E.g. 30 kg = 30 * 9.81 = 294.3 N 3.

3. Calculate the torque you get when the weight hangs on the horizontal pedal crank.
E.g. at 172.5 mm cranks : 0.1725m * 294.3 N = 50.77 Nm (Newton meter).

4. Switch the Powermeter on by pedalling backwards. Do this with a middle gea r so that the chain is in a line, e.g. 53/15.

5. Notice zero of Powermeter (MODE + SET, right number)
e.g. F0=500 Hz.

6. Bring crank in horizontal position and hang the weight on the left pedal.

7. Notice frequency output-left of Powermeter (MODE + SET, right number)
e.g. Fleft=1450 Hz.

8. Bring crank in horizontal position and hang the weight on the right pedal.

9. Notice frequency output-right of Powermeter (MODE + SET, right number)
e.g. Fright=1550 Hz.

10. Calculate frequency change of Powermeter with this weight as (Fleft+Fright)/2 -Fo
e.g. (1450+1550)/2 Hz - 500 Hz = 1000 Hz at a torque of 50.77 Nm.

11. Calculate average slope of Powermeter.
Slope = 1000 Hz/50.77 Nm = 19.90 H z/Nm.

12. This slope is the calibration of Powermeter and must be set in Powercontrol.
We recommend to check the slope monthly.


Is it possible to make these steps with a Garmin 810 unit?

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Posted: Sun Jul 07, 2013 5:11 pm 


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PostPosted: Tue Jul 09, 2013 12:18 am 
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Location: Canada
I am pretty sure it is NOT possible without a SRM head unit


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 Post subject: Calibrating Slope on SRM
PostPosted: Tue Jul 09, 2013 7:54 am 
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Location: Denmark
It is posible and even easier with a Garmin Edge unit as it doesn't leave the zero offset screen in the middle of the meassurements.

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PostPosted: Tue Jul 09, 2013 12:29 pm 
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Location: Canada
but then can you adjust the slope afterwards?


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PostPosted: Wed Jul 10, 2013 2:00 am 
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Location: USA
Yes, you can manually enter the slope on a Garmin


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