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Help with new Powertap and Edge 500
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So before posting this question, I took time to search using Google, search ST, check out Garmin's forums and both the Garmin and PT manuals.

I could not find specific instructions or guidelines on how to use the "Calibrate" feature on the Edge 500 when paired with a PT (I have the Pro+).

The questions I have are:

a) should calibration be performed while stopped -- right now if coasting, the Edge seems not to perform calibration, so I assume this is a yes but would love confirmation from someone else with the same setup.

b) more importantly, on the Edge 500 when I go into Settings > Bike Settings > Bike 1 > ANT+ Power > and click on Calibrate, I see the following message:

Calibration Successful
Current Calibration -18268

The auto zero function is "checked" or turned on.

Is this calibration value of any significance? I have friends using the Edge 500 with Quarqs and they've said they need to see a value within a specific range, so I wasn't sure if Powertap users have a similar guideline or if the number doesn't matter. I am thinking I will try a Computrainer ride to compare the numbers, but during the first ride I took with it today the power numbers seemed to be too high quite often.

Thanks in advance, I just couldn't find detailed info anywhere on the interwebs.

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Last edited by: trikicks: Oct 8, 10 19:41
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Re: Help with new Powertap and Edge 500 [trikicks] [ In reply to ]
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bump...i know i'm not the only person using an Edge 500 and PT here, can anyone help?
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Re: Help with new Powertap and Edge 500 [trikicks] [ In reply to ]
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Someone must have the same setup. I have an Edge 500 and was going to drop some cash for a Powertap, and would like to see the response. hopefully someone will give some good info.

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Re: Help with new Powertap and Edge 500 [B-Dub] [ In reply to ]
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Thanks. I was concerned (still am a little bit) because the power numbers displayed on the Garmin during my rides seem slightly high at certain points. I've yet to ride with the PT on the Computrainer to compare the difference.

FYI I setup my Garmin to display 3s power on screen and not instant power, to avoid seeing some of the jumpiness/spikes while riding.

I also called Saris today and their customer support was excellent. The rep said that if the Autozero function on the Garmin is turned on, there is nothing else you need to do since the Garmin head unit automatically zeroes out multiple times during a ride, so there should be no issue regarding the calibration. He did say I can try borrwowing a Cycleops computer/LYC from a friend, since you can actually see if the PT is calibrated correctly on those.
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Re: Help with new Powertap and Edge 500 [trikicks] [ In reply to ]
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1) the quarq manual is clear. Crank the crank backwards 5 times and have it endup at 12/6. That will reset the 0 offset. You should do this every time before you start riding

2) Edge 500 calibrate doesnt do a calibration. It just reports what the powermeter is currently using as its offset. (when you do the above procedure it send out an ant+ message with the offset)

3) if you are really reporting -18k your quarq is hosed and you need to talk to them.

Checkout http://www.iotexpert.com
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Re: Help with new Powertap and Edge 500 [alanhawse] [ In reply to ]
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Thanks, that is what I heard about the Quarq/Garmin calibration. I have a powertap so good to know I can ignore the offset number shown on screen.
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Re: Help with new Powertap and Edge 500 [trikicks] [ In reply to ]
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I have this setup and it works as you documented. I'm no guru, but when I get a 'Calibration Successful' message
and the PT reads zero when I'm coasting...life is good.

I had a wired PT previously, and it would read positive numbers (about 50W) when I coasted if it got out of calibration. After a few
years and thousands of miles, that went from happening 1-2 /year to being required on every ride (This was with the yellow PT computer)
and I sent it back to Saris for a rebuild/recalibration for about $250.

So - long story short - if you get zeros when you coast, you're probably OK.

.

" I take my gear out of my car and put my bike together. Tourists and locals are watching from sidewalk cafes. Non-racers. The emptiness of of their lives shocks me. "
(opening lines from Tim Krabbe's The Rider , 1978
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Re: Help with new Powertap and Edge 500 [TriDevilDog] [ In reply to ]
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thanks!

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