Powermeter temperature variations
amaferanga
Posts: 6,789
Simple questions really.
If I take my PowerTap from a nice warm house (~20 degrees Celsius) into a nice cold garage (~5 degrees Celsius) and just start riding on the turbo without doing a zero offset, will the power begin to over- or under-read as the hub cools? Does anyone know how many Watts error this might introduce?
I should say that usually I take my bike from the house (where it obviously lives) to the garage a good hour before riding and manually zero before each ride, but I have been known to forget to do a manual zero.
If I take my PowerTap from a nice warm house (~20 degrees Celsius) into a nice cold garage (~5 degrees Celsius) and just start riding on the turbo without doing a zero offset, will the power begin to over- or under-read as the hub cools? Does anyone know how many Watts error this might introduce?
I should say that usually I take my bike from the house (where it obviously lives) to the garage a good hour before riding and manually zero before each ride, but I have been known to forget to do a manual zero.
More problems but still living....
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Comments
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I forget which way the torque zero goes on a PT with a temp change (you need to have it in the test mode to find out as the PT's yellow computer head does not display negative units in the regular torque display mode).
Nevertheless, manually zeroing is a very good idea as the auto zero will not work if the T0 has moved too far from its current set point.0 -
I calibrated mine this morning just as I got out the door at 512. 30 mins of riding later when i got to work I calibrated it again, offset was 513.
Not sure if that means much or not...0 -
I only see the hub ID on my Garmin.More problems but still living....0
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I tend to put my bike outside for 60 minutes before riding, or as long as it takes me to get ready (usually longer as I am an ace procrastinator). Then calibrate before riding. But admittedly thats with SRMs not PT.--
Obsessed is just a word elephants use to describe the dedicated. http://markliversedge.blogspot.com0 -
That's what I usually do as well. But can anyone tell me which way the power would go if the PM is manually zero'd at say 20 degrees and then the temp drops to significantly less without doing any more manual or auto zeroing? It's not really an issue, I'm just curious and if anyone also has a ballpark 'number of Watts off' I'd also be interested to know.More problems but still living....0
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It depends on the power level and gear used, but a torque zero on a Powertap being out by 1 inch-pound (the smallest unit shown on the LYC display) will mean an error in power reading of ~ 1% to 3%. Lower the power, the bigger the error.amaferanga wrote:That's what I usually do as well. But can anyone tell me which way the power would go if the PM is manually zero'd at say 20 degrees and then the temp drops to significantly less without doing any more manual or auto zeroing? It's not really an issue, I'm just curious and if anyone also has a ballpark 'number of Watts off' I'd also be interested to know.0 -
I only see the hub ID on my Garmin.
What Garmin do you have?
Why would you not turn auto zero on?0 -
JimboPlob wrote:I only see the hub ID on my Garmin.
What Garmin do you have?
Why would you not turn auto zero on?
It is on (I never said it wasn't), but on the turbo I don't tend to coast.
Never mind.More problems but still living....0
