I'd been using an old Powertap SL+ hub along with the Joule GPS+. My Joule died. One of the mounting tabs broke and I got a little over over zealous in hacking a solution involving a screw... These are basically made for each other, so operation was pretty seamless. With the Joule I could do a zero calibration manually or automatically (coasting), check the torque reading, and do a "stomp" (hanging weight) test to check the PM's accuracy. Plus it used the hub's internal sensor for speed. With the Powertap software I'd export a detailed .csv file that had 1sec records of time, torque, speed, power, and gps coordinates, that I'd stick in a spreadsheet I made for doing Chung VE analysis. I needed torque because the power record always stayed "zero" for a couple seconds after coasting even though there was torque (a significant issue if doing half-pipes where there is a lot of coasting), and the GPS coordinates were used to determine heading so I could use a fixed ground wind direction and intensity in the analysis.
PT seems to be discontinuing the Joule, plus they are overpriced so I looked at alternatives. I wasn't having any luck finding detailed info on how exactly any of the computers would work with my PM, so I started at the bottom, and figured I'd work my way up if necessary. So I bought a Bryton 310 for $75, which seems to work great, except:
a)It doesn't appear to auto-zero (no selection anyway). It has a manual zero function but no way to tell if it worked.
b)There is no torque readout to check accuracy.
c)It doesn't pick up the speed sensor in the hub (uses GPS). So I'd need to get a different speed sensor.
d)Data (non standard .fit files), must go from the head unit to Bryton.com to Strava to Golden Cheetah to .csv file. I've already have determined that speed data on Strava is a little different than Bryton.com so I haven't bothered trying the other steps. Uploads to Strava from the Powertap software had similar weird issues. At any rate I want to keep translations to a minimum... preferably head unit file to .csv.
So. That didn't work :( I think a Garmin 520 will do what I want.** Anyone using a Wahoo Bolt for this? **
Head unit features: Zero calibration manually or automatically (both).
**Torque readout to check PM accuracy using a stomp (hanging weight) test. **
**Detailed .csv export. **
**GPS coordinates to calculate heading. If the heading was actually recorded, in the unit or in software, that would save me having to calculate it! **
**Read the PT hub speed sensor (not absolutely necessary, but definitely nice). **
I pronpbably understood less than 20% of what you wrote, however, I’ve been very happy with my Bolt.
Very simple to use. Turn it on, select calibrate for my PT hub, ride, then sync to Strava, etc. that’s all I need. The mapping works well when cycle touring.
Turn it on, select calibrate for my PT hub, ride, then sync to Strava, etc.
My Bryton does that…
So I guess you are doing a manual zeroing? What is the readout when you do that, does it display a torque value? Can you also select auto zero (zeros the PM when coasting).
Can you set it up to use either the PT hub for speed, or GPS?
I see Wahoo just came out with a firmware update to fix incorrect readings with a PT hub. Would have really pissed me off if I’d bought one a year ago. Is there a forum somewhere where people gripe about issues? The only one I found was on Google Groups.
BOLT WF09-1937 - 3 June, 2018
FIXED: Favero Assioma average power and cadence incorrectFIXED: PowerTap hub power meter data lowFIXED: Issue where user has to resync starred segments before each rideFIXED: Current grade data could fluctuate on a steady climbFIXED: bug with Garmin Vector power meter calibrationFIXED: bug causing issues with GPS accuracy during long rides (6+ hours)FIXED: bug causing sensor disconnects and failure to recover sensor connection after disconnect
I didn’t read most your post - but I have been riding with my Powertap Pro+for almost 10 years (with little yellow computer at first), then Garmin 510, then Garmin 520. It’s super simple and always works. I don’t know why you’re asking about calibration or zero’ing; I have never ever done that and always get consistent values. I thought in fact that this function wasn’t needed for anything anyways.
I don’t know why you’re asking about calibration or zero’ing; I have never ever done that and always get consistent values. I thought in fact that this function wasn’t needed for anything anyways.
All PMs are effected by temperature, that’s why you need to zero (calibrate) them. If your head units are set to auto-zero then it’s happening without your input, every time you coast. At least I assume this happens in the head unit rather than the hub itself.
I am pretty sure temperature compensation happens inside the powermeter through an extra strain gauge in the wheatstone bridge that is not subjected to strain (but only temperature) and provides the error voltage caused by temperature so the true voltage caused by strain is calculated.
There may be temperature compensation in the hub but it isn’t perfect. There is an additional procedure where the torque reading is zeroed when no load is applied. I think this is just something the head unit does rather than a change in the hub’s signal. For instance when coasting the head unit reads a torque offset of 508 in-lbs from the hub, so actual torque will be T-508.
All PMs are effected by temperature, that’s why you need to zero (calibrate) them. If your head units are set to auto-zero then it’s happening without your input, every time you coast. At least I assume this happens in the head unit rather than the hub itself.
I know only SRM cranks using the crank torque frequncy ANT+ protocoll don‘t performe auto-zero in the powermeter. For all other powermeter I know the head unit sends a single message to the powermeter requesting auto-zero on or off. After auto-zero is set on by the user via the head unit the power meter does not send any message to signal that the zero offset is changed.
For all other powermeter I know the head unit sends a single message to the powermeter requesting auto-zero on or off. After auto-zero is set on by the user via the head unit the power meter does not send any message to signal that the zero offset is changed.
For clarification, are you saying that the compensation is done at the PM level rather than the head unit? For instance if I have a head unit with an auto-zero setting, and I set that in the head unit, it’s the hub signal that behaves differently rather than the head unit applying an offset?
If so, I guess this would mean that auto-zero would be working on the Bryton, if hub that was already set that way…
There may be temperature compensation in the hub but it isn’t perfect. There is an additional procedure where the torque reading is zeroed when no load is applied. I think this is just something the head unit does rather than a change in the hub’s signal. For instance when coasting the head unit reads a torque offset of 508 in-lbs from the hub, so actual torque will be T-508.This happens in the powermeter. When the first power2max came out it didn’t have that, but then they added the extra hardware shortly after.
This happens in the powermeter. When the first power2max came out it didn’t have that, but then they added the extra hardware shortly after.
Interesting. So if I set the hub to auto-zero with a head unit that has that function, then it will likely still be on auto-zero when I’m using the Bryton?
This happens in the powermeter. When the first power2max came out it didn’t have that, but then they added the extra hardware shortly after.
Interesting. So if I set the hub to auto-zero with a head unit that has that function, then it will likely still be on auto-zero when I’m using the Bryton?
I’m watching this topic with interest.
When I bought my PT hub, I was under the impression it auto zeroed every time you coasted. That was a big influence on why I purchased it.
So. That didn't work :( I think a Garmin 520 will do what I want.
Head unit features: Zero calibration manually or automatically (both).
**Torque readout to check PM accuracy using a stomp (hanging weight) test. **
**Detailed .csv export. **
**GPS coordinates to calculate heading. If the heading was actually recorded, in the unit or in software, that would save me having to calculate it! **
**Read the PT hub speed sensor (not absolutely necessary, but definitely nice). **
The Garmin 520 has several features you listed in bold above:
Zero calibration manually or automatically
GPS coordinates
Read the PT hub speed sensor
It doesn’t provide torque readout, only calibration offset value. It exports data in FIT file format and not .csv. However, you can export activities uploaded to Garmin Connect to CSV files.
It doesn’t provide torque readout, only calibration offset value.
Thanks! I’m guessing if I get the zero offset value then I can still do the hanging weight test. I’ll just have to run the “calibration” with the weight on…? I still have a Powertap Cervo LYC with Ant+, and I can’t get Poweragent to read it’s files for some reason, but I think it will still work for torque testing.
BTW, I just bought a Garmin 520. $188 from Bike Tires Direct. Hope I like it.
